An excellent option for supporting a residential building would be a do-it-yourself strip foundation; step-by-step instructions will help you complete the work without errors. The result of the work will be a reliable foundation that can support even a brick building.
Before you make a strip foundation with your own hands, it is worth studying its design features. Depending on the technology used, the tape is of two types:
A - monolithic; b - prefabricated
A monolithic strip foundation will be a more profitable option for frequent construction. Prefabricated technology is more often used for mass construction. This is due to the fact that concrete blocks and prefabricated reinforced concrete foundation slabs are used for installation. Such structures are on average 1-2 meters long and weigh from a couple of hundred kilograms to a couple of tons.
The construction of a strip foundation made of blocks becomes impossible without renting lifting equipment: a tower or truck crane. This will significantly increase the cost of construction. In addition, in a small area, the problem of placing mechanisms arises.
Pouring a strip foundation avoids additional costs. This option is rational when building a house with your own hands. A few people will be enough to complete the work.
By design, the tape is of three types:
The first option is suitable for the construction of buildings on any basis. In this case, it is possible to make a basement or technical underground for utilities. The construction of a shallow-type strip foundation is considered for small buildings and in the case of non-heaving soils with good strength (coarse, medium or coarse sands) occurring on the site.
Unburied tape is used only for auxiliary buildings. You can put a gazebo or canopy on it. A properly selected type of foundation will be the key to the success of all work.
To choose materials for a strip foundation, you need to decide on the technology. When using prefabricated elements, you will need to purchase:
Sealing holes with brick or concrete is used because it is almost impossible to completely lay out an underground wall from standard blocks. Also, concrete and reinforcement will be useful to make a strip concrete belt along the edge of the supporting part. A reinforced concrete element is necessary to bind the entire structure into a single whole. It allows you to evenly transfer the load from the walls to the underlying parts. If necessary, read a detailed article about FBS foundations.
The technology of pouring a strip foundation involves the use of:
Before properly pouring a strip foundation under a house, you will also need to prepare bulk material. Use medium or coarse sand, crushed stone, gravel or a sand-gravel mixture. This pillow simultaneously performs several functions:
Before making the final decision to go deeper with the type of structures under consideration, it is worth studying the pros and cons of the types of strip foundations. A deep strip foundation has the following advantages:
A buried strip foundation also has disadvantages:
In some cases, a reasonable solution would be to install a shallow strip foundation. The option has the following advantages:
But the construction of a strip foundation of this type is not available in all cases. This reinforced concrete option has several disadvantages:
This question should be the most important when designing a structure. The buried strip foundation is supported so that its base is 20-30 cm below the freezing mark. This is the only way to protect the building from uneven deformations due to frost heaving.
The height of the strip foundation depends on the climatic characteristics of the area. The freezing depth is determined by formulas. But for a simplified calculation of the dimensions of the supporting part, you can use ready-made tables developed for different cities of the country.
Soil freezing depth by city
The shallow-depth design of the strip foundation involves its laying at a distance of 70-100 cm from the surface level. It is important to remember that this option has a lower load-bearing capacity and is not resistant to the forces of frost heaving.
Before you start concreting for your house, you need to carefully select the depth of the base. At the same time, not only freezing, but also ground water level is controlled. General rule: water should not be closer than 20 cm to the base of the building.
The foundations of low-rise buildings usually do not require detailed calculations. All values are assigned by eye. In this case, there is a high probability of cost overruns. But if possible, it is better to contact specialists who will accurately select the laying, width and reinforcement. If this is not possible, use the minimum values:
Making strip foundations is not such a difficult task. But you will need to carefully study all the nuances and components for private houses.
Strip foundation: device diagram
First of all, a strip foundation diagram must be prepared. All sizes are indicated on it. Such a drawing will make it possible not only to easily make a recessed strip foundation, but also to calculate in advance the required amount of materials.
Example of working drawing with dimensions
There is a certain order of work according to which a strip foundation is poured; the technology is as follows:
Preparation
How to make a strip foundation correctly? - Answer: do geology and calculations. You will also need to clear the area and remove debris.
Geological surveys are carried out by specialists. In a simplified version, you can make them yourself. In this case, holes are dug or wells are drilled to a depth that is 50 cm greater than the laying of the tape. The main task at this stage is to determine:
After the tests, the location mark is finally accepted, and the cross-section is assigned depending on the strength characteristics of the soil. Only an engineer can perform such work with high precision.
Site marking
For marking, use a wooden scrap and a cord. Another option is to draw lines along the ground using lime mortar. How to pour the foundation for a house with high precision? You need to try hard at the marking stage. It is worth preparing in advance a diagram of the strip foundation, which subsequently needs to be taken out to the area. The drawing made is needed so that all dimensions are at hand.
To mark, first mark the first corner. Then a side is built from this point. It is easier if this side is parallel to the fence or road. The next step is to construct a right angle. In such a situation, you need to use the Egyptian triangle method.
Cast-off stakes should be placed at a short distance from the outer walls of the building. This will prevent the cord from sagging when developing a trench or pit. After the markings for a square or rectangular building have been prepared, it is worth checking the dimensions of the diagonals. They must match. Deviation up to 20 mm is allowed. A house with a complex plan can be broken down into simple shapes.
To prepare the base for heavy equipment, you will need to mark out individual foundations. The expansion joint between them and the main tape is taken to be at least 10 cm. After pouring the structures, this space is filled with bulk non-combustible material.
Soil development
The technology requires a large amount of work. Most likely, additional equipment will be required: an excavator, dump trucks to remove soil outside the site. The scale of the work depends on whether the building will have a basement:
When performing earthworks, you must remember about safety precautions. The width of the trench must be such that formwork can be installed in it. The walls are made with a slight slope. To prevent soil from collapsing, temporary supports are installed. You should not work in the trench alone. There should always be another person on the surface to help in case of danger.
The dimensions of the trench or pit must provide unhindered access for workers to the side surface of the underground wall. This is necessary in order to insulate and waterproof the basement in the future. The width on each side of the tape increases by approximately 80 cm.
sand cushion
A sand (crushed stone or gravel) cushion is laid at the bottom of the pit or trench. Its thickness is determined depending on the strength of the soil from 20 to 50 cm. The weaker the soil, the thicker the bedding is needed. The same rule applies to heaving.
Sand cushion - the lowest layer of the base
The pillow must be level along its entire length. When laying it, it is compacted layer by layer (the thickness of the layer for compaction is taken to be no more than 15-20 cm. Compaction can be done by vibration or pouring water. The pouring method is not recommended for use for clay soils, since they have a low filtration coefficient.
A concrete preparation made of lean concrete B 7.5 with a thickness of 5-10 cm is placed on top of the pillow.
Drainage system
Drainage at the level of the tape base is used not only with high groundwater level. The device uses drainage pipes with a diameter of 110 to 200 mm. The choice of diameter is carried out depending on the geological conditions of the site. Pipes are laid with a slope of 0.003-0.01.
The drainage is installed in a layer of crushed stone with a fraction size of 20-40 mm. It performs a filtering function and prevents pipes from clogging. To prevent the crushed stone from spreading, it is wrapped in geotextile.
Drainage device at high groundwater level
When installing a drainage system, several rules are taken into account:
The system is discharged to an open area, to a septic tank or sewer.
Formwork work
There are two types of formwork for reinforced concrete foundations:
The second option also serves as thermal insulation and additional waterproofing. The formwork is placed strictly according to the markings. Its height is set 10 cm higher than the foundation. Supports are installed on the outside for stability. Jumpers can also be provided inside the structure. The first unit to be mounted is a corner one. Plastic film or roofing felt is placed in wooden formwork, which prevents the leakage of cement laitance.
The upper edge of the formwork is placed 2-5 cm above the concrete mark. This will allow you to compact the mixture without any problems. It won't splash. The fill mark is drawn on the inner surface of the formwork with a marker.
Installation of fittings
Reinforcing cages consist of three types of rods:
It is recommended to make all connections using a binding wire. Welding weakens the reinforcement and does not provide a high guarantee. Even if the rods are connected along the main length with a welding machine, wire is used at the corners. To reduce labor intensity, a knitting gun is used.
Sample placement of reinforcing frame
in a strip foundation
The pitch of the clamps is set on average to 20-30 cm. In places where the walls adjoin each other, the pitch is halved. Before carrying out work, you should carefully study the methods of reinforcing the foundation in nodes. Read the rest of the rules and recommendations in the article about reinforcement of strip foundations.
Pouring concrete
Before pouring a strip foundation under a house, it is recommended to order the mixture at the factory. This allows you to perform work without interruption. Also in the factory it is easier to maintain the proportions of components, which are very important. By adding a little more crushed stone or sand, you can get weaker concrete than required.
Pouring concrete
It is recommended to use material of classes from B15 to B20 for filling. The heavier the house (from frame to brick), the more durable the concrete will be required. It is advisable to perform the filling in one day (non-stop). This is the only way to prevent the appearance of concrete seams that weaken the structure.
When performing work, you should follow the basic rules:
Concrete maintenance and stripping
Before building a house, you need to study the weather forecast. It is recommended to perform pouring at an average daily temperature of +20 degrees Celsius. In hotter weather, the quality of the material decreases; in colder weather, the hardening speed decreases. In total, it takes 28 days to gain strength.
Immediately after pouring, the structure is covered with polyethylene, tarpaulin or burlap. This will prevent moisture loss too quickly. The formwork can be removed upon reaching 70% of the brand value. At an average daily temperature of +20°, this will take one or two weeks.
The film maintains the required humidity conditions during hardening
During the first week after laying the mixture, you need to water it with water at intervals of a couple of hours. This will avoid the appearance of cracks on the surface of the structure. One of the ways to wet the surface is to scatter sand or sawdust over the concrete; during maintenance, these materials are already wetted. They will gradually release moisture to the concrete.
Insulation and waterproofing
Insulation from moisture is mandatory. It includes:
Insulation is carried out if necessary (if a warm basement is planned). It is not allowed to use mineral wool for these works. The best option would be extruded polystyrene foam (“Penoplex”).
DIY strip foundation: step-by-step instructions with photos
When building a house or other buildings, preference is most often given to a strip foundation, since such a foundation has many advantages. A strip foundation for a house is quite simple to install and, if necessary, it can be poured without the involvement of construction equipment. Such a foundation is a universal design and is used in the construction of light wooden and heavy stone buildings on various types of soil. We will look in more detail at what a strip foundation is, its types, and how it is installed in our article.
Sectional strip foundation Source bayanay.info
Before proceeding with the construction of such a foundation, it is necessary to carefully consider its features and varieties. This will allow you to choose the right foundation for the construction of a particular structure. This will also make it possible to carry out all the necessary work correctly. A strip foundation is not just one way to make a foundation for a house; there are several types:
A monolithic or solid strip foundation is constructed directly at the construction site. To begin with, formwork is constructed into which a reinforced belt is laid along its entire length. After this, concrete is poured.
The base is a closed monolithic contour made of reinforced concrete. Thanks to this, you can create a solid frame that is suitable for any soil, including unstable ones. On such a foundation you can easily build a country house or a stone fence.
Among the advantages of this design are ease of construction and reliability. In this case, the base can have a different shape. As for the disadvantages, there is a large mass of the monolithic structure.
Solid strip foundation - concrete is poured in one step into the prepared formwork Source sazhaemvsadu.ru
Ready-made reinforced concrete blocks are used to construct the foundation. They are used to lay out a tape of the desired shape directly on the site. They are held together using cement mortar. They are optimally suited for the construction of low-rise buildings. It is quite easy to purchase ready-made blocks, since many factories are engaged in their production.
Among the advantages, it is worth highlighting the ease of assembly, which can significantly save time on foundation construction. But, at the same time, prefabricated structures have some disadvantages. The non-solid structure and the need to attract heavy construction equipment reduces the popularity of this type of strip foundation.
For reference! If we talk about the price of the issue, the difference between prefabricated and monolithic strip foundations is insignificant. Therefore, when choosing, you should focus on the structural features.
A prefabricated strip foundation is assembled from ready-made slabs, and the joints between them are sealed Source kinozavr.info
This type of foundation is mainly used in the construction of light buildings. So, these can be frame houses and structures made of timber and logs. The peculiarity of this foundation is that it is located slightly above the soil freezing level. Therefore, it is often used on less problematic soils.
Shallow structures easily tolerate soil heaving that occurs in winter. During construction, special attention is paid to waterproofing and thermal insulation. This will protect the base from the negative effects of the environment.
The advantages of a shallow foundation include its low construction cost. At the same time, there is no need for complex earthworks. It has several disadvantages. First of all, it is worth noting that this design cannot be used on all types of soil and for the construction of not all structures.
The design of a shallow foundation is standard - it is simply buried into the ground no more than 50-70 centimeters Source novostroika93.ru
On our website you can find contacts of construction companies that offer foundation design and repair services. You can communicate directly with representatives by visiting the “Low-Rise Country” exhibition of houses.
The construction of a strip foundation of this type is carried out below the freezing level of the soil. This makes it possible to distribute the load from the future structure onto a stable layer of soil. Due to this, deep foundations are used for the construction of multi-story buildings that have significant weight.
The advantage of this design is that they are suitable for the construction of heavy structures. It is also possible to equip the basement and basement. Of course, arranging the foundation will require significant physical and material costs. This is especially true for excavation work.
A deep strip foundation is buried below the soil freezing level - this can be 1.7-2.2 meters or lower, depending on the region Source diagnostika.spb.ru
To find out the approximate cost of a strip foundation, use the following calculator:
When choosing a foundation, you should pay attention to the advantages and disadvantages of one or another option. This also applies to monolithic strip construction. The benefits include:
Unfortunately, strip foundations have some disadvantages:
It is worth considering that the concept of pros and cons is ambiguous, since everything here depends on the depth of the structure. Therefore, each type of foundation must be considered separately.
To make the base you will need various materials. It all depends on its type. So, for the construction of a prefabricated foundation, the following materials are used:
Photo of the foundation with collapsible formwork:
One of the waterproofing options is laid during the formwork assembly process. Source readmehouse.ru
It is almost impossible to lay out a tape exclusively from blocks. Therefore, concrete mortar and even bricks are used to fill gaps. It is also recommended to install a reinforced concrete strip, which will allow all the elements to be connected into one.
As for the monolithic structure, for its construction you will need:
When constructing a strip foundation for a house, it is worth considering that there is a need for certain work. This applies to the arrangement of the pillow. To do this you will need sand or crushed stone, as well as waterproofing material.
Designing a foundation is a very complex and responsible task, the solution of which is best left to professionals. During this process you need to determine:
Scheme of arrangement of strip foundation drainage Source krovli-zabori.ru
In order to determine these values, you must have certain knowledge. That is why it is better to entrust this work to professionals. Only they can do it efficiently. It is worth remembering that the strength and durability of not only the foundation, but also the structure built on it will depend on this.
Arranging a basement in a house with a strip foundation is a very labor-intensive and costly process. To resolve this issue, it will be necessary to involve construction equipment and carry out false earthen and concrete work. The arrangement of the basement is carried out in the following sequence:
When constructing walls, special attention should be paid to their height. They must coincide with the top point of the foundation. After constructing the base, the basement is covered by pouring a monolithic slab.
The depth of the foundation is calculated at the design stage. The buried structure is installed so that its base is 25 cm below the soil freezing level. This will protect it from uneven deformations that occur during frost heaving of the soil.
The height of the structure depends on the climatic characteristics of a particular area. The freezing depth is determined by the formula. But, there is a ready-made table where you can find these values for a particular region.
Approximate depth of soil freezing in various regions of the Russian Federation and the CIS Source izchegopostroit.ru
If we talk about a shallow foundation, it is located at a distance of 85 cm from the soil freezing level. When constructing a structure, it is worth considering that it will have a low load-bearing capacity. Also, when constructing the foundation, it is worth taking into account the groundwater level. The sole should be located at a distance of 20 cm from it. So, how to make a strip foundation?
Making a strip foundation is not such a difficult task. But in order to do the job correctly, you need to carefully study all the nuances and requirements. And you should start by drawing up a design diagram. The dimensions of the elements are indicated on it, which will make its construction easy. Also, using this scheme, you can calculate the required amount of materials.
The strip foundation technology looks something like this:
At the preparation stage, calculations, markings and other equally important work are carried out. It’s worth starting with geological recovery - this work is trusted exclusively to specialists.
To carry out geological surveys competently, you need special equipment and specialized knowledge. Source ro.decorexpro.com
During the geological recovery process, the following must be determined:
After this, the elevation and thickness of the monolithic tape are calculated. When the geological penalties are completed, they begin marking the site. To do this, use a wooden board and cord. You can also use lime mortar. With its help, a mark is made on the ground where the tape will pass. To simplify the task, the work is carried out using a pre-prepared foundation diagram.
Marking starts from one corner. After this, a party is planned. It is better to do it parallel to the fence or road. Then the other side is outlined and so on. In this case, it is worth carefully checking the corners and diagonals. This will avoid problems with the construction of walls. The permissible error between diagonals is 2 cm.
According to the applied markings, a pit or trenches are dug. The first option is used when constructing houses with a basement. This will require the use of heavy construction equipment.
Why the foundation is being prepared, see the following video:
A sand cushion is placed at the bottom of the prepared pit or trench. The thickness of the embankment can reach 50 cm. This parameter depends on the characteristics of the soil. The pillow is carefully compacted. This is done by vibrating or pouring water. A prepared layer is made on top of the pillow. To do this, pour thin concrete no more than 10 cm thick.
The construction of a strip foundation is carried out using the following types of formwork:
The peculiarity of the second option is that polystyrene foam plays the role of a heat and waterproofing layer. The formwork is placed strictly according to the applied markings. It rises 10 cm above the foundation. To ensure the stability of the structure, it is supported by supports from the inside and outside. A polyethylene film is placed in the formwork, which will prevent the leakage of cement laitance.
A mark is made on the inside of the formwork to mark the top point of the concrete. A marker is used for this. In the process of carrying out this work, a hydraulic level is used. This will allow the concrete to be poured evenly.
What permanent waterproofing formwork looks like, see the following video:
To make a frame, three types of reinforcement are used, which perform a specific task:
Before buying reinforcement, you need to calculate how much it will be needed to build the frame. It is worth taking into account the features of its design. The distance between the clamps is on average 25 cm. In the corners and at the joints of the walls, the pitch is slightly reduced. When reinforcing, certain standards and requirements must be observed.
For more information about reinforcement, watch the following video:
Now you need to decide how to fill the strip foundation? If it is of significant size, then it is better to order a ready-made concrete solution, which will allow you to fill the formwork in one go.
When concreting, you should adhere to some rules:
It is best to pour a strip foundation at an average daily temperature of about 20°C. After completion, the structure is covered with plastic film, which will slow down moisture loss.
For a clear overview of the entire technology for creating strip foundations, see the following video:
Although the construction of a strip foundation seems quite simple, it requires a lot of effort and materials, and the cost is about a third of the entire construction budget. A good foundation is calculated for the project of a specific house and it is better to entrust this work to professionals. Do not forget that the service life of the structure will depend on the quality and strength of the foundation.
The concept of “strip foundation” characterizes only its shape. In practice, for low-rise buildings, there are several technology options for manufacturing a base of this shape. We will briefly talk about some of them and provide instructions for the step-by-step construction of a monolithic foundation.
There are two types of tape based on depth. If the sole is no deeper than 60 cm, then this is a shallow foundation.
This also includes bases when the sole is on the surface of the ground. And to be more precise, a little lower, taking into account that the site is leveled. In practice, such a foundation in its pure form is placed where there is no fertile layer. Such conditions are rare. In most cases, there is a humus layer on the construction site, so the layout of a non-buried foundation looks like this:
But more common is a foundation buried in the ground up to 60 cm.
All these options are common in private construction, when the project does not provide for a basement. It has been proven that heaving forces at shallow depths are compensated by the weight of a low-rise building, and the load-bearing capabilities of a shallowly buried belt are sufficient to withstand the loads.
The bottom of the buried one lies in the ground below the freezing point.
This type is the most durable, but it is also the most material-intensive. It is laid when a basement or underground technical floor is needed to accommodate engineering systems equipment.
According to the manufacturing method, there are three types of base tape: prefabricated, monolithic, combined. And these technologies already have their own subtypes.
The prefabricated base is usually assembled from concrete blocks (FBS).
They also use a “smaller format”: ceramic brick or cinder block. But even with a foundation made of solid building blocks, the load-bearing capacity is weakened by the seams - and even reinforcing belts cannot fully compensate for this. Therefore, a pure brick or cinder block foundation is rarely found, and building blocks go to the base of combined foundations.
If for FBS a mortar is needed to fill the unevenness of the spoon and there are no special requirements for the brand (the adhesion strength of the blocks is ensured by the weight), then when using “small forms” a full-fledged masonry mortar is required. In addition to assembling from FBS, foundations made from medium-sized natural stone are also popular.
And the popularity can be explained simply - high decorative properties.
Combined foundations can also have different technological schemes. For example, an underground part made of reinforced concrete plus a brick base.
Monolithic tape comes in two types: with rubble stone filled with concrete, and reinforced concrete.
In the first option, the reinforcing role is assigned to a small-sized rubble stone. Unlike a “pure” rubble foundation, a rubble concrete foundation involves: installation of formwork, laying a cushion, pouring a small layer of concrete, laying the first row of stone into it, pouring a layer of mortar, laying the second row, etc. The distance between the stones is maintained at about 5 cm, and the ratio of the volumes of mortar and stone is approximately 1:1.
The attractiveness of this type of foundation is that it reduces the volume of concreting and, consequently, the cost of materials.
But the most reliable is a monolithic concrete strip with a reinforcing frame.
The manufacturing technology has the following sequence.
A pit (for a deep foundation) or a trench system (for a shallow foundation) is marked on the ground. Excavation work is being carried out.
If the tape is shallow and communications enter/exit under the sole, then a trench is dug for them and sleeves are laid for laying pipes under the tape. Level (plan) the bottom of the pit or trenches. The sand and gravel bed is filled, leveled, moistened and compacted. The total thickness of the cushion is up to 30 cm (the ratio and volume of the parts depend on the characteristics of the soil), and the width of the cushion is 30 cm wider than the heel of the foundation. Install the formwork.
The materials are edged boards and timber. It is allowed to use edged boards with wane, but so that there are no gaps between them.
To simplify the assembly procedure, you can make shields from boards and timber on the ground. The thickness of the formwork walls must withstand the pressure of the concrete. The strength of the formwork is increased by connecting the racks horizontally with steel wire and strengthening them with side stops on the ground on one or both sides.
For a deep foundation, when constructing a basement, it is recommended to install permanent foam formwork.
At the formwork of the buried foundation, holes are cut for sleeves for utility lines. For sleeves, sections of plastic or asbestos concrete pipes are used. The diameter of the sleeve is selected based on the size of the passing pipes and the insulation layer. During foundation work, the sleeves are filled with sand and the holes are closed.
Install a reinforcing frame. The reinforcement diameter and mesh parameters depend on the calculated load-bearing properties. The main purpose of the “iron” is to improve the resistance of the foundation to fracture and lateral loads; the compressive strength of concrete stone is already high. The distance between the reinforcement and the walls of the formwork is at least 50 mm.
Concrete is poured in layers. If there are access roads and a concrete plant nearby, then it is better to use a ready-made mixture.
Otherwise, prepare the mixture yourself, observing the proportions to obtain the required brand.
The optimal layer thickness is up to 20 cm. And the filling of the layer should be continuous around the entire perimeter. Each layer is compacted in one of the following ways: with a deep vibrator or bayoneted with a piece of reinforcement (for small volumes).
After pouring the last layer, it is covered with plastic film (this is a necessary condition for normal hydration of concrete). It is allowed to cover the base part of the foundation with burlap and periodically wet it. The first seven days are critical, when the concrete stone gains 70% of its design strength.
After four weeks, the formwork is removed. Then waterproofing is carried out. The choice of materials and technology depends on the nature of the soil and groundwater level. Popular are roll materials that are fused onto the prepared surface.
The construction of buildings begins with a load-bearing foundation, which determines not only the service life of the structure itself, but also shapes the comfort and microclimate inside the premises. Strip foundations are one of the most popular types of foundations used both for the construction of private housing and for the construction of technical buildings.
A strip foundation is a load-bearing foundation, which is a closed loop in the form of a strip of reinforced concrete, brick and block building materials. The tape is erected under the load-bearing walls of the building, which contributes to the uniform distribution of the load and its further transfer to the underlying layers of the soil.
For the manufacture of monolithic strip foundations, high-strength concrete grades are used
The design of the strip foundation allows the construction of buildings both from wood and foam concrete, and from brick and concrete blocks. When constructing a foundation, a large amount of excavation and construction work is required. Despite this, strip foundations are popular both among summer residents and owners of suburban areas, as well as among professionals.
The foundation is laid on a pre-compacted bed of sand and gravel. After hardening, the supporting tape is covered with an insulating material that will protect the integrity of the reinforced concrete surface. If the total weight of the structure being erected is small (up to 50 tons), then the preparation of the underlying cushion can be neglected.
The configuration of the supporting tape depends on the shape of the walls of the building being constructed
The competitive advantages of strip foundations include:
The disadvantages include the fact that the construction of a strip foundation is a very labor-intensive process that requires the investment of a considerable amount of finance. On average, the cost of a load-bearing foundation is 15–20% of the total budget allocated for building a house.
The foundation construction technology assumes that the tape will be poured during a work shift, and it is problematic to prepare such a volume of concrete mixture even with the help of a concrete mixer. Because of this, there is a need to purchase concrete from the manufacturer, which is also a significant waste.
According to SNiP 3.02.01–87 “Earth structures, foundations and foundations”, strip load-bearing foundations are classified according to two criteria:
The depth of the foundation depends on the bearing capacity of the soil and the design load that will be exerted on the foundation being built. The bearing capacity of the soil is determined based on its type, freezing depth and the presence of groundwater in the area where the building is planned to be built. Read about the design and method of constructing a strip foundation in the next section.
A shallow strip foundation is a strip of concrete and a reinforcing frame located at a shallow depth in the ground. The minimum laying level depends on the depth of soil freezing, its heaving and the height of groundwater.
A shallow strip foundation can be made of reinforced concrete, brick or foam blocks
For example, if the groundwater is high and the depth of soil freezing is large, then the foundation will be affected by both lateral and tangential heaving forces, which will compress and displace the shallowly buried load-bearing tape. And vice versa - the lower the groundwater level and the higher the level of soil freezing, the less the impact of heaving forces.
The recommended minimum depth of the strip foundation can be found in SNiP II-B.1-62. For your reference, we offer a table compiled based on data from this document. On average in Russia, the laying depth varies from 0.4 to 0.75 m. Additionally, you can consider the depth of seasonal soil freezing in the region where it is planned to lay the load-bearing foundation.
The depth of laying a shallow strip foundation in the central region of Russia should not be less than 0.5 m
The construction of shallow strip foundations is recommended in the following cases:
The construction of a shallow strip foundation on soil consisting of peat, sapropel, silt and other organic deposits is strictly prohibited. It is not recommended to build this type of strip foundation on mixed and heaving soil types that are oversaturated with moisture.
A buried foundation or deep foundation is a load-bearing reinforced concrete or prefabricated strip located 20–30 cm lower than the freezing level of the soil.
The depth of laying the carrier tape can reach 1.5–2 m, depending on the level of soil freezing
The main idea of deep laying of the load-bearing tape is to rely on dense layers of soil that have a higher load-bearing capacity. This type of foundation involves even larger volumes of excavation work and the cost of concrete mixture.
The construction of a deep strip foundation is recommended:
In addition, a buried foundation allows you to build a basement. With high-quality insulation and sufficient insulation, it is possible to arrange a basement floor intended for living or storing things.
Depending on the design features, strip foundations can be monolithic or prefabricated. They, in turn, can be divided into monolithic foundations with vertical supports and prefabricated strips made of brick or foam block.
When installing a monolithic strip foundation, reinforcement and pouring of the foundation are carried out directly at the construction site. As a result, the overall integrity and continuity of the carrier tape is achieved.
A monolithic strip foundation is a continuous reinforced concrete strip along the entire perimeter of the building
Depending on the geology of the site, the depth of a monolithic foundation varies from 80 to 250 cm. When constructing private houses, the depth of laying rarely exceeds 150 cm.
Monolithic types of foundations, regardless of technology, are used for the construction of objects for various purposes on heaving and moving types of soil. The solidity of the structure ensures high strength and reliability of the load-bearing base.
Pile-tape and column-tape foundation types are a monolithic strip of reinforced concrete located on supports buried in the ground. Essentially, these types of foundations - nothing more than a modernized version of pile or columnar foundations with a grillage.
Pillars or piles are located along the perimeter of the foundation in increments of 2 m
In the first case, steel products in the form of piles of various lengths are used as supports, which are screwed into the ground manually or automatically. In the second, the supports are made from the same concrete mixture that is used to fill the supporting tape.
The arrangement of pile and columnar strip foundations is justified only when constructing objects in areas with a large depth of soil freezing. Steel piles or reinforced concrete pillars, buried below the freezing level of the soil, will distribute the load that is transmitted from the reinforced concrete strip.
The main material for the construction of a prefabricated strip foundation is reinforced concrete foundation blocks (FBC), made from heavy grades of concrete. The blocks form a load-bearing foundation strip, which is located along the perimeter and area of the future structure. To connect the blocks to each other, concrete grade M350 and steel reinforcement Ø15 mm are used.
After assembling the foundation, the outer surface of the load-bearing base is treated with waterproofing materials. The most commonly used are bitumen mastic and special bitumen membranes that have a self-adhesive base.
Prefabricated strip foundation consists of reinforced concrete foundation blocks connected by concrete
The main advantage of a prefabricated strip foundation is the short construction time. Unlike a monolithic base, you do not have to wait for the concrete mixture to reach the minimum strength. You can start building a house within a few days from the moment the tape is assembled.
Despite this advantage, prefabricated strip foundations are used for the construction of private houses a little less frequently than a monolithic concrete foundation. This is largely due to the fact that the prefabricated structure is not suitable for use on moving types of soil. With the same thickness, the strength indicators of a prefabricated structure are 20–30% lower than a monolithic one.
Brick strip foundations are a prefabricated structure and are often used for the construction of one-story houses using frame technology. Burnt solid brick is used to make the tape. Laying depth - 40–50 cm.
A brick strip foundation is highly repairable, but requires high-quality waterproofing
After assembly, as in the case of blocks, it is necessary to install a full waterproofing layer. The advantages of this foundation include:
If we make a more detailed comparison of bricks with reinforced concrete blocks, then foundations made of blocks are less hygroscopic and have higher strength. Brick is more fragile, which affects not only the frequency of repairs, but also the service life of the structure as a whole. Taking this into account, it is recommended to build a brick strip foundation in areas with dry and hard soil, as well as in areas with low groundwater levels.
In order to begin the construction of a strip foundation, you will need to perform calculation operations, during which you need to find out the depth of the foundation and the width of the supporting strip. If possible, these works can be delegated and contacted by a design and construction organization, where they will calculate all the necessary parameters on the basis of which a project for the future foundation will be drawn up.
If you decide to carry out soil surveys and draw up a project yourself, then be prepared that even a small mistake made can lead to the destruction of the house. Especially if you are planning to build a two- or three-story building.
| Type of building | Depth of strip foundation (cm) depending on soil type | ||||||
| Rocky soil, opoka | Dense clay, soft loam | Packed dry sand, sandy loam | Soft sand, silty soil | Very soft sand, sandy loam, silty soil | peat bog | ||
| Barn, bathhouse, outbuildings. the buildings | 20 | 20 | 30 | 40 | 45 | 65 | |
| One-story cottage with attic | 30 | 30 | 35 | 60 | 65 | 85 | A different type of foundation is needed |
| Two-story dacha | 50 | 50 | 60 | Requires specialist calculations | Requires specialist calculations | A different type of foundation is needed | |
| Multi-storey cottage | 70 | 65 | 85 | Requires specialist calculations | Requires specialist calculations | Requires specialist calculations | A different type of foundation is needed |
For low-rise buildings made of wood, garages, bathhouses, chicken coops and technical buildings, calculations can be performed taking into account the recommendations given in SNiP II-B.1-62 “Foundations of buildings and structures”.
The simplest option is to check the known parameters with a special table that allows you to determine the depth of the strip base. The table mentioned is shown above. For reference: 1 kN = 101.9 kg. The table was compiled based on European standards adopted in 2010.
To level the area, improvised means, hand tools and special equipment are used.
As an example, let's calculate the parameters of the strip foundation required to build a one-story dacha made of timber, the length of which is 8 m and the width is 6 m. The height of the dacha, not including the roof, is 2.5 m. The structure will be built on the ground of dry fine sand. The depth of soil freezing is 1.4 m, which corresponds to the central part of Russia.
The sequence for calculating a strip foundation is as follows:
Based on this, we can conclude that the previously indicated width of the supporting tape (0.2 m) is ideal for a one-story dacha weighing no more than 100 tons. As a result, it turns out that to build a timber dacha with an area of 48 m2, a strip foundation 0.2 m wide is required, which will be buried 0.6 m into the ground.
Using the tables given in this article and SNiP 2.02.01–83, you can perform a calculation for any strip foundation that will be erected on non-heaving soil types. Data on the weight of building materials can be taken from open sources, and online calculators can be used for rough calculations.
After all calculation operations have been completed and a design for the foundation and future building has been received, you can proceed to preparing the land plot. During preparation, it is necessary to clean and mark the surface of the area using available means.
Marking the area for a strip foundation is done using wooden pegs and a strong rope that is stretched between them
To prepare, you will need to complete the following steps:
For the final check, it is necessary to measure the diagonals of the foundation site. To do this, the thread is pulled crosswise. If everything is done correctly, the diagonals will be equal. Otherwise, you need to double-check the corners using the device and rearrange the pegs.
During excavation work, it will be necessary to dig trenches to the design depth, which is calculated taking into account the type of soil and the foundation being built. To do this, you can use both special equipment and hand tools in the form of shovels and crowbars.
The trench for the strip foundation is dug to the design depth of the load-bearing foundation and underlying cushion
To arrange trenches around the perimeter of the foundation, you will need to perform the following activities:
For the manufacture of formwork, edged boards of 20×150, 20×175 or 20×299 mm are used, which are fastened with wooden blocks of 50×50 mm. If possible, you can use moisture-resistant plywood, which is mounted on a pre-assembled timber frame. The principle of constructing formwork panels is shown in the photo below.
Installation of formwork is carried out in the following sequence:
If the foundation provides for the laying of pipes for communications and the creation of ventilation gaps, then special holes of the required cross-section are cut into the formwork. For this, an electric drill with a crown attachment is used.
To reinforce the strip foundation, a frame made of steel reinforcement Ø12–15 mm is used. The frame is assembled by welding or using steel wire.
The knitting of the reinforcing frame occurs as follows:
When knitting, remember that the frame must be hidden under a layer of concrete to a depth of 5–6 cm. The maximum length of the lintel with a tape width of 40 cm should not exceed 30 cm.
To speed up the knitting process, you can purchase a special construction gun, which works on the principle of a stapler, but instead of the usual staples, it uses steel wire of the required cross-section.
When constructing strip foundations for private housing, a concrete mixture of grade M200, M250, M300 or M350 is used. Concrete grade M200, as a rule, is used only for small frame baths and utility rooms. Concrete of higher grades is for pouring foundations for the construction of two- and three-story houses, and concrete M350 is only for large buildings.
The foundation is poured strictly in one step, so it is important to ensure the required volume of concrete mixture, which is calculated based on the size of the foundation. If it is not possible to prepare the required amount of concrete, then the foundation is poured in layers with the obligatory compaction of each layer.
The proportions of the solution when mixing the mixture yourself are 1 part cement, 2 parts sifted sand and 4 parts crushed stone of fraction 20–40. When changing the proportions of the solution, you should remember that there should be 1.5–2 times more crushed stone than sand.
Automated supply of concrete mixture will greatly speed up the process of pouring a strip base
You can start pouring the mixture from any convenient place in the trench. Concrete is supplied in portions so that it can be evenly distributed throughout the volume of the trench. To compact the mixture, a reinforcement rod or wooden lath is used.
The last portion of concrete is leveled along the tensioned guideline. To do this, raw concrete is filled with dry cement and rubbed with a wooden float. After this, the foundation is covered with plastic film and moistened with a small amount of water 2-3 times a day.
The concrete strip foundation will gain full strength no earlier than after 27 days, but after 14–17 days the formwork can be dismantled. After 27–30 days, the foundation is waterproofed and backfilled.
Despite the relatively high cost, strip foundations are one of the most durable types of load-bearing foundations. In addition, many owners of summer cottages prefer this type of foundation, as it allows them to equip a basement or even an entire basement.
Everyone knows the old proverb that a real man must do three things in his life: plant a tree, raise a son and build a house. With the last point, especially many questions arise - what material is better to use, choose a one- or two-story building, how many rooms to count on, with or without a veranda, how to install the foundation and many others. Among all these aspects, the foundation is fundamental, and this article will be devoted to its strip type, its features, differences, and construction technology.
Despite the fact that there are several types of foundations for a house, preference in modern construction is given to strip foundations. Thanks to its durability, reliability and strength, it occupies a leading position in the construction industry around the world.
Already from the name it is clear that such a structure is a tape of a set width and height, laid in special trenches along the boundaries of the building under each of the external walls, thus forming a closed contour.
This technology gives the foundation extreme rigidity and strength. And through the use of reinforced concrete when forming the structure, maximum strength is achieved.
Among the key features of the strip foundation type are the following:
According to GOST 13580-85 standards, a strip foundation is a reinforced concrete slab, the length of which is from 78 cm to 298 cm, the width is from 60 cm to 320 cm and the height is from 30 cm to 50 cm. After calculations, the grade of the base with a load index of 1 is determined up to 4, which is an indicator of the pressure of the walls on the foundation.
In comparison with pile and slab types, the strip base, of course, wins. However, a columnar foundation overpowers the base with tape due to the significant consumption of materials and increased labor intensity.
This figure is influenced by:
The service life of a strip foundation directly depends on the correct choice of site for construction, compliance with all requirements and building codes. Taking into account all the rules will extend the service life for more than one decade.
An important feature in this matter is the choice of building material:
Tape foundation construction technology can be used:
Among all the many advantages, it is worth mentioning some of the disadvantages of a strip foundation:
By classifying the selected type of foundation according to the type of device, we can distinguish between monolithic and prefabricated foundations.
Continuity of underground walls is assumed. They are characterized by low construction costs in relation to strength. This type is in demand when building a bathhouse or a small wooden house. The disadvantage is the large weight of the monolithic structure.
Monolithic foundation technology involves a reinforced metal frame, which is installed in a trench and then filled with concrete. It is due to the frame that the necessary rigidity of the foundation and resistance to loads is acquired.
Cost per 1 sq. m - approximately 5100 rubles (with characteristics: slab - 300 mm (h), sand cushion - 500 mm, concrete grade - M300). On average, a contractor will charge about 300-350 thousand rubles for pouring a 10x10 foundation, taking into account installation and the cost of materials.
A prefabricated strip foundation differs from a monolithic one in that it consists of a complex of special reinforced concrete blocks connected to each other through reinforcement and masonry mortar, which are mounted using a crane at the construction site. Among the main advantages is a reduction in installation time. The downside is the lack of a unified design and the need to attract heavy equipment. In addition, the strength of a prefabricated foundation is inferior to a monolithic one by as much as 20%.
Such a foundation is used in the construction of industrial or civil buildings, as well as for cottages and private houses.
The main costs will be for transportation and hourly rental of a truck crane. 1 linear meter of prefabricated foundation will cost no less than 6,600 rubles. About 330 thousand will have to be spent on the base of a building with an area of 10x10. Laying wall blocks and pillows with a small distance will allow you to save money.
There is also a strip-slotted subtype of construction, which is similar in its parameters to a monolithic strip foundation. However, this base is adapted for pouring exclusively on clay and non-heaving soils. Such a foundation costs less due to the reduction of earthworks, since the installation takes place without formwork. Instead, they use a trench, which visually resembles a gap, hence the name. Slotted foundations allow you to equip a garage or utility room in low-rise, non-massive buildings.
Important! Concrete is poured into wet soil, since in a dry trench some of the moisture goes into the ground, which can cause the quality of the foundation to deteriorate. Therefore, it is better to use concrete of a higher grade.
Another subtype of prefabricated strip foundation is cross. It includes glasses for columns, support and intermediate plates. Such foundations are in demand in row building conditions - when a columnar foundation is located close to a foundation of the same type. This arrangement is fraught with subsidence of structures. The use of cross foundations involves the contact of the grid of end beams of the building under construction with an already constructed and stable structure, thereby allowing the load to be evenly distributed. This type of construction is applicable for both residential and industrial construction. Among the disadvantages is the labor intensity of the work.
Also, for a strip foundation type, a conditional division can be made regarding the laying depth. In this connection, according to the magnitude of the load, buried and shallow types are distinguished.
Deepening is carried out below the established level of soil freezing. However, within private low-rise buildings, a shallow foundation is acceptable.
The choice in this typing depends on:
Determining the listed indicators will help in choosing the right type of strip foundation.
The recessed type of foundation is intended for a house made of foam blocks, heavy buildings made of stone, brick, or multi-story buildings. Such foundations are not afraid of significant differences in height. Perfectly suitable for buildings in which it is planned to equip the ground floor. It is erected 20 cm below the soil freezing level (for Russia this is 1.1-2 m).
It is important to take into account the frosty buoyancy forces of heaving, which should be less than the concentrated load from the house. To confront these forces, the foundation is set in the shape of an inverted "T".
The shallowly buried belt is distinguished by the ease of construction that will be located on it. In particular, these are wooden, frame or cellular structures. But its location on the ground with a high groundwater level (up to 50-70 cm) is undesirable.
The key advantages of a shallow foundation are the low cost of building materials, low labor intensity and short installation time, in contrast to a buried foundation. In addition, if it is possible to get by with a small cellar in the house, then such a foundation is an excellent and low-cost option.
Disadvantages include the inadmissibility of installation in unstable soils., and such a foundation will not be suitable for a two-story house.
Also, one of the features of this type of foundation is the small area of the lateral surface of the walls, and therefore the buoyant forces of frost heaving are not harmful to light construction.
Today, developers are actively introducing the Finnish technology for installing foundations without deepening - pile-grillage. The grillage consists of slabs or beams that connect the piles to each other above the ground. The new type of zero-level device does not require the installation of panels and the installation of wooden blocks. In addition, there is no need to dismantle the hardened concrete. It is believed that such a structure is not subject to heaving forces at all and the foundation is not deformed. Installed on formwork.
In accordance with the standards regulated by SNiP, the minimum depth of the strip foundation is calculated.
Strip foundations are mainly installed from brick, reinforced concrete, rubble concrete, using reinforced concrete blocks or slabs.
Brick is suitable if the house is to be built frame or with thin brick walls. Since brick material is very hygroscopic and easily destroyed due to moisture and cold, such a buried foundation is not welcome in places with high groundwater levels. It is important to provide a waterproofing coating for such a base.
The popular reinforced concrete base, despite its cheapness, is quite reliable and durable. The material contains cement, sand, crushed stone, which is reinforced with metal mesh or reinforcement rods. Suitable for sandy soil when constructing monolithic foundations of complex configuration.
A strip foundation made of rubble concrete is a mixture of cement, sand and large stone. A fairly reliable material with parameters of length - no more than 30 cm, width - from 20 to 100 cm and two parallel surfaces up to 30 kg. This option is perfect for sandy soils. In addition, a prerequisite for the construction of a rubble concrete foundation must be the presence of a gravel or sand cushion 10 cm thick, which simplifies the process of laying the mixture and allows you to level the surface.
The foundation made of reinforced concrete blocks and slabs is a finished product manufactured at the enterprise. Among the distinctive features are reliability, stability, strength, and the ability to be used for houses of various designs and types of soil.
The choice of material for constructing a strip foundation depends on the type of device.
The prefabricated base is made:
Before a project is drawn up and the parameters of the building’s foundation are determined, it is recommended to review the regulatory construction documents, which describe all the key rules for calculating the foundation and tables with established coefficients.
Among these documents:
GOST 25100-82 (95) “Soils. Classification";
GOST 27751-88 “Reliability of building structures and foundations. Basic provisions for calculation";
GOST R 54257 “Reliability of building structures and foundations”;
SP 131.13330.2012 “Building climatology”. Updated version of SN and P 23-01-99;
SNiP 11-02-96. “Engineering surveys for construction. Basic provisions";
SNiP 2.02.01-83 “Foundations of buildings and structures”;
Manual for SNiP 2.02.01-83 “Manual for designing foundations of buildings and structures”;
SNiP 2.01.07-85 “Loads and impacts”;
Manual for SNiP 2.03.01; 84. “Manual for designing foundations on a natural foundation for columns of buildings and structures”;
SP 50-101-2004 “Design and installation of foundations and foundations of buildings and structures”;
SNiP 3.02.01-87 “Earth structures, foundations and foundations”;
SP 45.13330.2012 “Earth structures, foundations and foundations.” (Updated edition of SNiP 3.02.01-87);
SNiP 2.02.04; 88 “Foundations and foundations on permafrost soils.”
Let us consider in detail and step by step the calculation plan for the construction of the foundation.
To begin with, a total calculation of the entire weight of the structure is made, including the roof, walls and ceilings, the maximum permissible number of residents, heating equipment and household installations, and the load from precipitation.
You need to know that the weight of the house is determined not by the material from which the foundation is made, but by the load that is created by the entire structure made of various materials. This load directly depends on the mechanical features and the amount of material used.
To calculate the pressure on the sole of the base, it is enough to sum up the following indicators:
The first point is calculated by using the formula snow load = roof area (from the project) x established parameter of snow cover mass (different for each region of Russia) x correction factor (which is affected by the angle of inclination of a single- or gable roof).
The established parameter of snow cover mass is determined according to the zoned map SN and P 2.01.07-85 “Loads and impacts”.
The next step is to calculate the potential payload. This category includes household appliances, temporary and permanent residents, furniture and bathroom equipment, communication systems, stoves and fireplaces (if available), and additional utility routes.
There is an established form for calculating this parameter, calculated with a margin: payload parameters = total structure area x 180 kg/m².
In the calculations of the last point (load of parts of the building), it is important to list as much as possible all the elements of the building, including:
Moreover, to calculate the sum of all the above elements, two methods are used - mathematical and the results of marketing calculations in the building materials market.
Of course, there is also the option of using a combination of both methods.
The first method's plan is:
The marketing calculation method is based on data from the Internet, the media and reviews of professionals. The specified specific gravity is also summed up.
The design and sales departments of enterprises have accurate data, where it is possible to call them to clarify the nomenclature or use the manufacturer’s website.
The general parameter of the load on the foundation is determined by the summation of all calculated values - the load of parts of the structure, useful and snow.
approximate specific pressure = mass of the entire structure / dimensions of the base area.
Having determined these parameters, an approximate calculation of the geometric parameters of the strip foundation is permissible. This process occurs according to a certain algorithm established during research by specialists from the scientific and engineering department. The scheme for calculating the size of the foundation depends not only on the expected load on it, but also on the construction documented standards for deepening the foundation, which, in turn, are determined by the type and structure of the soil, groundwater level, and freezing depth.
Based on the experience gained, the developer recommends the following parameters:
Soil type | Soil within the calculated freezing depth | Interval from the planned mark to the groundwater level during the freezing period | Foundation installation depth |
Non-heaving | Coarse, gravelly sands, large and medium-sized | Not standardized | Any, regardless of the freezing limit, but not less than 0.5 meters |
Heaving | The sand is fine and dusty | Exceeds the freezing depth of more than 2 m | Same figure |
Exceeds the freezing depth by at least 2 m | Not less than ¾ of the calculated freezing level, but not less than 0.7 m. |
||
Loam, clay | Less than the calculated freezing depth | Not less than the calculated freezing level |
The width of the strip foundation should not be less than the width of the walls. The depth of the pit, which determines the height of the base, should be designed for a 10-15 centimeter sand or gravel cushion. These indicators allow further calculations to determine: The minimum width of the foundation base is calculated depending on the pressure of the building on the foundation. This size, in turn, determines the width of the foundation itself, which presses on the soil.
This is why it is so important to do a soil examination before starting to design a structure.
Rubble stone:
Rubble concrete:
Clay brick (ordinary):
Concrete (monolith):
Concrete (blocks):
Next, it is important to optimally adjust the parameters by adjusting the norms of specific pressure on the soil of the sole in accordance with the calculated soil resistance - the ability to withstand a certain load of the entire structure without settling.
The calculated soil resistance must be greater than the parameters of the specific load from the building. This point represents a significant requirement in the process of designing the foundation of a house, according to which in order to obtain linear dimensions it is necessary to simply solve an arithmetic inequality.
When drawing up a drawing, it is important that this difference be 15-20% of the specific load of the structure in favor of the soil’s ability to withstand pressure from the building.
In accordance with the types of soil, the following calculated resistances are derived:
100 kPa = 1 kg/cm²
Having adjusted the results obtained, we obtain approximate geometric parameters of the foundation of the structure.
In addition, today's technologies make it possible to significantly simplify calculations using special calculators on developer websites. By indicating the dimensions of the base and the building material used, you can calculate the total cost of building the foundation.
To install a strip foundation with your own hands you will need:
When planning to build a structure on a site, it is worthwhile to first examine the site where construction is planned.
There are certain rules for choosing a place for the foundation:
Having determined that the selected area complies with all standards, you should begin marking the area. First of all, it needs to be leveled and rid of weeds and debris.
For marking work you will need:
The first marking line is decisive - it is from it that all other boundaries will be measured. It is important to establish an object that will serve as a guide. This could be another structure, a road or a fence.
The first peg represents the right corner of the building. The second is installed at a distance equal to the length or width of the structure. The pegs are connected to each other with a special marking cord or tape. The rest are hammered in the same way.
Having defined the external boundaries, you can move on to the internal ones. For this purpose, temporary pegs are used, which are installed at a distance of the width of the strip foundation on both sides of the corner markings. Opposite marks are also connected to each other by a cord.
Lines of load-bearing walls and partitions are installed using a similar method. Potential windows and doors are highlighted using pegs.
When the marking stage is completed, the cords are temporarily removed and, following the marks on the ground, trenches are dug under the external load-bearing walls of the structure along the entire perimeter of the marking. The internal space is torn out only if a basement or basement is planned.
The established requirements for carrying out excavation work are specified in SNiP 3.02.01-87 on earthworks, foundations and foundations.
The depth of the trenches must be greater than the calculated depth of the foundation. Do not forget about the mandatory preparatory layer of concrete or bulk material. If the excavated excavation significantly exceeds the depth taking into account the reserve, this volume can be replenished with the same soil or crushed stone, sand. However, if the overshoot exceeds more than 50 cm, you should contact the designers.
It is important to take into account worker safety - the excessive depth of the pit requires strengthening the walls of the trench.
In accordance with regulatory documents, fastenings are not required if the depth is:
Typically, for the construction of a small building, the average trench depth is 400 mm.
The width of the excavation must correspond to the plan, which already takes into account the thickness of the formwork, the parameters of the underlying preparation, the protrusion of which beyond the lateral boundaries of the base is allowed at least 100 mm.
The usual parameters are the width of the trench equal to the width of the tape plus 600-800 mm.
Important! To ensure that the bottom of the pit is a perfectly flat surface, you should use a water level.
This element represents the form for the intended foundation. Wood is most often used as the material for formwork due to its availability in terms of cost and ease of implementation. Removable or permanent metal formwork is also actively used.
In addition, depending on the material, the following types differ:
Classifying formwork depending on the type of structure, there are:
Grouping the types of formwork according to thermal conductivity, they differ:
The structure of the formwork is:
For installation you will need the following materials:
The amount of materials listed depends on the parameters of the strip foundation.
The installation itself requires strict adherence to the established requirements:
Step-by-step instructions for arranging continuous formwork for a strip base:
The installation of a stepped structure goes through several stages. Each subsequent tier of formwork is preceded by another similar tier:
Installation of stepped formwork is also possible at once, similar to the mechanism for assembling a continuous structure. In this case, it is important to adhere to the horizontal and vertical arrangement of the parts.
During the formwork construction phase, a significant issue is the layout of ventilation openings. Vents should be located at a minimum height of 20 cm from the ground surface. However, it is worth taking into account seasonal flooding and varying the location depending on this factor.
The best material for the ventilation hole is a round plastic or asbestos-cement pipe with a diameter of 110-130 mm. Wooden beams tend to stick to the concrete base, which makes them difficult to remove later.
The diameter of the vents is determined depending on the size of the building and can reach from 100 to 150 cm. These ventilation holes are located in the walls strictly parallel to each other at a distance of 2.5-3 m.
With all the need for vents, there are cases when the presence of holes is not required:
The correct choice of reinforcement is facilitated by understanding the variety of material classifications.
Depending on the manufacturing technology, the fittings may vary:
Depending on the surface type, the rods:
By purpose:
Most often, reinforcement in accordance with GOST 5781 is used for strip foundations - a hot-rolled element, applicable for conventional and prestressing reinforced structures.
In addition, in accordance with the grades of steel, and therefore the physical and mechanical properties, the reinforcement bars vary from A-I to A-VI. For the manufacture of elements of the initial class, low-carbon steel is used; in high classes, properties close to alloy steel are used.
In planned areas with the greatest load, mounting fittings are installed in the direction of the expected additional pressure. Such places are the corners of the structure, areas with the highest walls, the base under a balcony or terrace.
When installing a structure made of reinforcement, intersections, junctions and corners are formed. Such a poorly installed unit can lead to a crack or subsidence of the foundation.
That is why for reliability we use:
It is important to remember that each class of reinforcement has its own specific parameters for the permissible bending angle and curvature.
The parts are connected into a solid frame using two methods:
You can make a hook if you take a thick and durable metal rod. A handle is made on one edge for more convenient use, the other is bent in the form of a hook. Fold the mounting wire in half to form a loop at one end. Then it should be wrapped around the reinforced knot, inserting the hook into the loop so that it rests on one of the “tails”, and the second “tail” is wrapped around the mounting wire, carefully tightening it around the reinforcing rod.
All metal parts are carefully protected with a layer of concrete (minimum 10 mm) to prevent acid corrosion.
Calculations of the amount of reinforcement that will be needed for the construction of a strip foundation require determining the following parameters:
SNiP standards indicate the parameters of the total cross-sectional area of longitudinal reinforcement elements, which will be at least 0.1% of the cross-sectional area.
It is recommended to pour a monolithic foundation with concrete in layers 20 cm thick, after which the tier is compacted with a concrete vibrator to avoid voids. If you pour concrete in winter, which is undesirable, then you need to insulate it using available materials. In dry seasons, it is recommended to use water to create a damp effect, otherwise this may affect its strength.
The consistency of the concrete should be the same for each layer, and pouring should be done on the same day, since a low level of adhesion (a method of adhesion of surfaces of dissimilar solid or liquid consistencies) can lead to the formation of cracks. In the event that it is impossible to fill in one day, it is important to at least generously water the surface of the concrete and, in order to maintain dampness, cover the top with plastic film.
The concrete must settle. After 10 days, the outside walls of the base are treated with bitumen mastic and a waterproofing material (most often roofing felt) is glued to protect against water penetration.
The next stage is backfilling the cavities of the strip foundation with sand, which is also laid in layers, carefully compacting each tier. Before laying the next layer, the sand is watered.
A properly installed strip foundation is the key to long years of operation of the building.
It is important to strictly maintain a constant foundation depth over the entire area of the construction site, since minor deviations lead to differences in soil density and moisture saturation, which jeopardizes the reliability and durability of the foundation.
Among the common omissions during the construction of the foundation of a building are mainly inexperience, inattention and frivolity in installation, as well as:
To avoid such mistakes, it is fundamentally important to contact only specialists involved in installing the foundations of structures and try to follow the stages of construction. If you still plan to install the base yourself, before starting work it would be preferable to consult with specialists in this field.
An important topic when building a foundation is the question of the recommended time of year for such work. As mentioned above, winter and late autumn are considered undesirable times, since frozen and wet soil leads to inconvenience, slowdown of construction work, and, importantly, shrinkage of the foundation and the appearance of cracks in the finished structure. Professionals indicate that the optimal time for construction is warm and dry periods (depending on the region, these periods fall in different months).
Sometimes, after the foundation has been erected and the building has been in operation, the idea of expanding the living space of the house comes to mind. This issue requires a close analysis of the state of the foundation. If the construction is insufficiently strong, it can lead to the foundation bursting, sagging, or cracks appearing on the walls. Such an outcome can lead to the complete destruction of the building.
However, if the condition of the foundation does not allow you to complete the building, do not be upset. In this case, there are some tricks in the form of strengthening the foundation of the structure.
This process can be carried out in several ways:
The most important thing when building any type of foundation is to correctly determine the required type, carry out a thorough calculation of all parameters, carry out all the steps exactly according to the instructions, follow the rules and advice of experts and, of course, enlist the support of assistants.
Strip foundation technology is in the next video.
