In this article we will look at how to make a strip foundation with your own hands. Why is it so important to make the right strip foundation? Let's find out the structure and types of strip foundations. What is a shallow strip foundation, pile strip foundation, monolithic strip foundation and how do they differ? Let's find out how to calculate a strip foundation and what kind of reinforcement is needed for a strip foundation. And also many many other questions so that you can clearly understand how to make a strip foundation with your own hands.
Let's first look at what types of strip foundations exist. Knowing this information will help in choosing your future foundation for your home. Not only the final cost of construction, but sometimes also the safety of residents depends on the correct choice of strip foundation for a house. After all, the wrong choice of foundation type can have disastrous consequences. Up to the destruction of the entire structure of the house. So let's get started.
Shallow strip foundation.
As the name itself suggests, a shallow strip foundation for a house differs from a buried foundation in its depth. You may have a question: exactly what depth should a strip foundation be in order for it to be considered shallow? We answer: this value should be less than the depth of soil freezing in your area. This also entails the features associated with this type of foundation.
Since the soil under such a foundation can freeze, this circumstance must be taken into account when designing. Freezing soil expands, which means it will push the foundation and everything built on it upward. And not always evenly. This may result in various distortions of the building, and an uneven load on the foundation can break the foundation. To prevent this from happening, the shallow foundation must have sufficient reinforcement, calculated on our website. You can find them in the top menu.
In what cases is a shallow foundation for a house most often chosen?
- When there is no heaving soil under the house (stone, sand, etc.).
- When the groundwater level is low enough.
- When drainage is done around the house.
- When an insulated blind area is made around the building.
- When the structure being built is sufficiently light and movable (for example,).
If you decide to choose this type of foundation for your building, try to avoid mistakes when planning it, taking into account all the above circumstances. After all, a shallow strip foundation has an undoubted advantage: it is quite strong and relatively cheap.
Pile strip foundation.
In fact, this type of foundation is not strip. The correct name for a pile-strip foundation is a pile-grillage foundation. And it’s exactly in this form: piles plus grillage, that’s what needs to be done. But some of our craftsmen do it easier for them. The piles and foundation strip are poured directly on the ground or by deepening it shallowly. As a result, in winter, this ribbon and piles protrude from the ground. Soil gets into the voids under the piles and in the spring, when the earth returns the foundation to its place, it will be distorted or cracked. We do not recommend that you make a pile-grillage foundation in this way. There must be a sufficient gap between the grillage and the ground to allow for the expansion of the ground due to frost heaving.
Recessed strip foundation.
And finally, the most frequently poured type of foundation is recessed. Its depth should be greater than the freezing point of the soil. It is made either in the form of a monolithic reinforced concrete strip, or made from FBS concrete blocks, which are placed on a reinforced concrete pad. An armored belt is made from such blocks on top of the masonry to fasten the foundation into a single whole.
DIY strip foundation. Step-by-step instruction.
How to make a strip foundation? How to pour a strip foundation? Let's try to formulate the answers to these and other questions in the form of consistent, step-by-step instructions. We hope that even a beginner who decided to make a strip foundation with his own hands will understand these instructions. So, instructions.
- We decide what type of strip foundation we will make.
- We make a drawing of a strip foundation. The strip foundation diagram will help us determine its depth (height) and width. The depth of the foundation depends on its type (shallow, recessed). The height depends on whether you will make the base as a continuation of the foundation or whether you will make it from a different material. For example, from brick or basement blocks. It is recommended to make the height of the base equal to the average height of the snow cover in your area. The width of the strip foundation depends on the width of the walls of your future home. Depending on the material of the walls, it is allowed to make the foundation a quarter less wide than the width of the walls.
- The strip foundation reinforcement scheme is important, so we do it too. We can give general recommendations on which reinforcement for a strip foundation is suitable and how to reinforce a strip foundation. The diameter of the reinforcement used is usually in the range of 10-16 mm. The reinforcement is located 20-30 mm from the lower and upper edges of the foundation strip. The number of reinforcing threads depends on the width of the foundation (usually 2-3 threads at the top and bottom). If the foundation is planned to be more than 400 mm high, then vertical reinforcement is also performed with reinforcement 8-12 mm in diameter every 300-500 mm. In difficult cases, entrust the design of the foundation to a specialist. Incorrect reinforcement can ruin all your work.
- We calculate the strip foundation using a calculator.
- Select the brand of concrete or type of FBS blocks. If you are making a monolithic reinforced concrete foundation, then the appropriate grade of concrete for a strip foundation will be no lower than M200. The blocks are selected based on the dimensions you need in width, height and length.
- We mark the future strip foundation. We place wooden structures in the corners in the shape of the letter P. We stretch the thread or fishing line, marking the walls of the foundation. We make sure that the resulting rectangle has the same lengths of diagonals. After installing the external walls of the house, we perform the same manipulations for all internal load-bearing walls.
- We dig a trench. Don’t forget to constantly monitor its depth with a laser level, level, etc. The bottom of the trench should be located in a single horizontal field.
- We place it at the bottom of the trench, cover it with a layer of coarse sand about 10-15 cm and tamp it. We spill the sand with water and tamp it again.
- We install waterproofing. You can use film, roofing felt, etc.
- We expose the reinforcement frame. We place either pieces of stones or fragments of brick under the lower reinforcement bars, or you can place a protective layer of concrete on special plastic clamps. You can see how to properly knit reinforcement for a strip foundation in this article.
- Then we carry out the work based on the type of soil on your site. If the soil is dense, such as clay, you can pour a concrete strip foundation directly into the soil. And then we build the formwork for the base and fill the remaining part. Or we lay out the base from stone, brick, etc. If the soil is loose, then we erect the formwork immediately.
- The formwork for a strip foundation is made from boards of at least 30 mm thickness, with vertical supports every 50 cm. Or you can make formwork panels from timber and sheet material: plywood, OSB boards, etc. If you want to keep the boards or slabs intact and free from concrete, cover the inside of the formwork with film. Please note that only dense construction film with a thickness of at least 100 microns is suitable.
- We fix the formwork around the perimeter. We don’t skimp on this material, because... concrete is very heavy and will easily crush a light, unsupported structure. To fix the formwork panels, they often use studs (threaded rods) passed through sections of plastic water pipe to protect them from concrete.
- We pour concrete into the formwork. The strip foundation is poured in one go. In extreme cases, the foundation can be poured several times, but in this case, this is done in layers. There should be no vertical breaks. Concrete grade for strip foundations M200 and higher.
- Sprinkle the freshly poured concrete with a thin layer of cement (you can use a sieve) and cover it with waterproofing.
- For the first few days, you will need to water the hardened concrete well to prevent cracking.
- Then you can remove the formwork. The foundation can be loaded a week after pouring.
For a block strip foundation we do the same thing. We pour a concrete support pad, place FBS blocks on it, fastening them with cement mortar. Then on top of the blocks we make 
- If you have a basement, then you need to waterproof the strip foundation. Usually this is a bitumen-based coating waterproofing.
- Then the strip foundation is insulated. It is carried out with extruded polystyrene foam. White regular polystyrene foam is not suitable because... destroyed by moisture.
If you are not making your own basement, then you can apply horizontal waterproofing from roofing felt or coating penetrating waterproofing on top of the foundation strip. The strip foundation for the house is ready. You can carry out and build the house further.
The requirements for the foundation are very high.
The strength and reliability of the foundation are among the main, but not the only tasks assigned to supporting structures.
- Not buried. It is created on absolutely motionless soils - rocks, strong stable soils. It is extremely rare.
- Shallow. Used for construction on durable soils not subject to frost heaving. The depth is less than the level of winter soil freezing.
- Recessed. The depth of such a tape is slightly below the soil freezing level. Used for the most massive and heavy buildings, suitable for most types of soil and hydrogeological conditions.
The choice of the appropriate type is determined by an analysis of all site conditions - soil composition, number and properties of layers, depth of soil water, etc.
What buildings is it suitable for?
Strip foundations are a reliable support for buildings made of various materials:
- Tree.
- Foam and aerated concrete.
- Brick.
- Concrete plates.
The material and number of floors determine the weight of the building, on which the design parameters of the tape depend - the degree of penetration and thickness. Along with the soil characteristics, the building parameters are the main material for performing engineering calculations during design.
How to calculate depth
strip foundation depends on the type of foundation. E if construction is planned option, then it is necessary to rely on the tabular data of SNiP, displaying the depth of soil freezing in a given region.When constructing a shallow type of belt, the composition of the soil, the presence and depth of groundwater are taken into account. The optimal depth is usually considered to be 0.75-1 m, but on stable and dry soils the depth can be slightly reduced.
NOTE!
The most common immersion depth for a shallow belt is considered to be 0.7 m.
How is a shallow strip foundation constructed?
Almost completely repeats the recessed version, only with a lower level of immersion.There is a trench in which a drainage layer of backfill is created and a concrete strip is poured.
The base design has fewer capabilities than a full-fledged tape, but for relatively small low-rise buildings its load-bearing capacity is quite sufficient.
Step-by-step DIY installation instructions
Let's consider the procedure for creating a strip foundation:
- Preparation.
- Site marking.
- Digging a trench.
- Laying and arrangement of the drainage system.
- Creation of sandy.
- Production of formwork.
- Installation of reinforcement cage.
- Pouring concrete.
- Wait for hardening.
- Stripping.
- Waterproofing and insulation tape.
- Further work.
The order of actions does not change under almost any circumstances, since all stages are a consequence of previous operations.
Surface marking
The beginning of work consists of removing the top layer of soil and marking the area. For this, wooden stakes are used, which are installed at the intersection points or corner points of the future trench.
The width is selected based on the calculated parameters of the base, but at least 20 cm greater than that of the tape. This is important, since it will be necessary to install formwork inside the trench, and subsequently ensure a sufficient thickness of the backfill layer for the sinuses.
Preparing the trench
Digging a trench is done with an excavator or manually. The second option is difficult, but if difficulties arise with the delivery or approach of construction equipment to the site, it is quite possible. The excavated soil is stored on the sides of the trench or immediately removed from the site.
It is necessary to ensure the same depth, but there is no need to try too hard and level the bottom down to centimeters. The corners of the trench are aligned manually, regardless of the digging method.
Drainage device
The drainage system allows groundwater to be removed from the sand cushion layer, eliminating the possibility of heaving loads occurring in winter.
There are different types of systems:
- Open. It is created on the daytime surface and is intended to drain rain or melt water. Used on dry soils with deep groundwater.
- Closed. Consists of a pipeline system placed in a trench near the belt. Serves to remove groundwater from a layer of sand backfill (pillow), used on soils with the presence or seasonal changes in the level of soil water.
In practice, the closed type is most often used, since there is a danger of water in most cases. A special-purpose pipeline system is installed that receives and discharges moisture into a drainage well.
For high-quality drainage to work, it is necessary to install a filtration piping and have a slope for the natural movement of water. The filtration layer cuts off small organic particles, preventing the inner surface of the drainage pipes from silting.
This helps extend the life of the system and reduces the risk of failure.
Pillow
The sand cushion is an important and mandatory element of the base structure. Its thickness varies, on average it is 20 cm. Typically, clean river sand is used or alternately a 10 cm layer of sand, 10 cm of fine crushed stone and again a 5 cm leveling sand layer.
After filling each layer, careful compaction is carried out using construction vibrating machines or hand tools. It is recommended to shed the layers with water, this helps to seal the pillow better.
NOTE!
Experts recommend following the following criteria for the quality of compaction of the backfill layer: there should be no traces of shoes left on the surface when walking. This is important, since settlement of the cushion is unacceptable, as it will cause deformation of the tape with unpredictable consequences.
Installation of formwork
To create the formwork, edged boards with a thickness of 25-40 mm are used (depending on the size of the tape). First, shields with a width slightly exceeding the height of the tape are assembled next to the trench. As they are assembled, the shields are lowered into the trench and fixed from the outside with inclined stops and vertical support bars.
Crossbars are installed from the inside, defining the distance between the panels equal to the width of the tape. The formwork must be strong, ready to accept loads when concrete is poured and hardened. There should be no gaps; all gaps larger than 3 mm must be filled with tow or clogged with slats.
This will eliminate wasteful consumption of concrete when leaking into the cracks.
Reinforcement
Reinforcement is designed to compensate for tensile axial loads that concrete cannot withstand. It easily takes a lot of pressure, but when bending the tape is unstable and breaks immediately.
For reinforcement, a reinforcing belt is created, the main element of which is horizontal working rods made of metal or fiberglass ribbed reinforcement.
To support the rods in the required position, smooth rods of smaller diameter are used, from which vertical elements (clamps) are made, which, in combination with the working rods, form a spatial lattice.
Its dimensions are such that the horizontal rods are immersed in concrete to a depth of 2-5 cm.
Working rods are selected based on the width of the tape. Their diameter for a shallow base is in the range of 12-14 mm (with a width of 30-40 cm) or 16 mm with a larger width.
Knitting reinforcement
The connection of reinforcement frame elements is made in two ways:
- Electric welding.
- Knitting with soft steel annealed wire.
The first option is used for thick rods and is practically not used when constructing shallow foundations. The assembly of the arm belt most often occurs using the knitting method.
A soft wire is used, which quite reliably holds the frame elements, but has a certain degree of freedom, which allows maintaining the integrity of the frame when loads occur during pouring.
For knitting, a special hook-shaped tool is used. A piece of wire about 25-30 cm long is folded in half. The resulting half-loop wraps around both connecting rods in a diagonal direction, the ends rising upward.
Then grab the fold loop with a hook and, leaning on the second free end, make 3-5 rotational movements, due to which both rods are tightly and firmly connected to each other.
The operation is simple, usually the skill is developed on the first day.
Selecting concrete for pouring
There are quite a few grades of concrete designed for different conditions and loads. Since shallow strip foundations are mainly used in low-rise private construction, the optimal choice would be M200 grade concrete.
It is able to provide the necessary strength and load-bearing capacity of the belt with a relatively low dead weight.
For those who want to approach the issue more carefully, we can recommend using an online calculator to calculate the grade and amount of concrete. The result obtained should be duplicated on another resource to protect yourself from possible errors.
Fill
Filling must be done as quickly as possible, ideally at once. Breaks in pouring for more than a day are unacceptable; in such cases, it is necessary to keep the concrete until it hardens completely and only then continue work. The quality and strength of such a tape is much lower than that of simultaneous casting.
This condition is most easily met by using ready-mixed concrete, which is delivered directly to the site in the mixer. The result is a significant saving of time, and the quality of the concrete will in any case be better than that of a homemade solution.
It is necessary to pour from several points, trying to distribute them as evenly as possible along the length of the tape.. This will allow you to obtain a casting with the same parameters around the entire perimeter, which will ensure high strength of the base.
Features of waterproofing
Exposure to moisture is extremely detrimental to shallow tape. Penetrating into concrete, water sooner or later freezes and tears the material from the inside. This should not be allowed under any circumstances.
There are two types of waterproofing that you can do:
- Horizontal. Protects the lower and upper plane of the tape from moisture penetration from the lower layers of soil and from rain or melt water flowing from the walls. The lower waterproofing is laid before installing the formwork and reinforcing belt, and the upper one is done after the concrete has completely hardened in parallel with the vertical waterproofing. Both layers consist of roofing felt laid in two layers coated with bitumen mastic.
- Vertical. Apply to the outer and inner surface of the tape after stripping and complete drying. Materials of different types of action are used - impregnation, coating or pasting. Impregnations are the most effective, but they appeared relatively recently and are little known to builders.
Insulation issues
Insulation of the tape eliminates the formation of condensation. There are two options - external and internal insulation. In the first case, the insulation is installed from the outside, in the second - from the inside.
Experts recommend performing both types of insulation at the same time, since it is impossible to achieve the expected result separately. Taking into account the specifics of placement, it is necessary to use moisture-proof types of heat insulators - foundation penoplex, liquid polyurethane foam, polyethylene foam, etc.
Mineral wool should not be used in this case, as it can absorb water with complete loss of performance.
Proper care of concrete after pouring
After pouring, it is necessary to regularly water the surface of the tape with water for 10 days.:
- The first 3 days - every 4 hours.
- The next 7 days - 3 times a day.
The tape must be hidden from the scorching rays of the sun under a layer of polyethylene. Watering with water allows you to somewhat equalize the moisture content of the outer and inner layers of the tape, reducing loads and the risk of cracks.
The final hardening of concrete takes a very long time, but you can continue working with the tape after 28 days.
Stripping
Stripping is the procedure for dismantling formwork. It can be done no earlier than 10 days after pouring.
You should not try to speed up the process; the foundation is too important an element of the building to take risks and rely on chance.
Basic mistakes
Most often, sedimentation of the sand cushion occurs due to poor compaction of the backfill layer. In addition, the use of unsuitable materials, especially concrete of the wrong grade, is often encountered.
Some unscrupulous suppliers deliver low-quality material to save money. Experienced experts recommend ordering heavier concrete - instead of M200, take M250. The difference in cost and weight is small, but there is hope that the material will be more durable.
In addition, they often try to reduce the cost of money and labor by abandoning and. These procedures require some time, but, compared to the service life of the base, they are performed very quickly and cannot be neglected.
Useful video
In this video you will learn how to install a strip foundation:
Conclusion
Creating a strip foundation is not so much a difficult task as it requires a full understanding of the meaning of all stages and high-quality implementation of the necessary actions.
For an untrained person with no experience, it is recommended not to deviate from the technology and strictly comply with the requirements of SNiP.
This will help build a strong and high-quality shallow strip foundation.
In contact with
A shallow strip foundation (MSLF) is a type of strip foundation, which is located 0.3-0.7 m below the zero level. The construction of this type of foundation requires a minimum of financial and labor costs. MZLF is excellent for light buildings erected on various soils. The foundation has its advantages and disadvantages, as well as a special construction technology.
Shallow strip foundation: scope of application, pros and cons
The bearing capacity of MZLF, in comparison with foundations of other types, is assessed as average and largely depends on the type of soil on the site. A shallow foundation is suitable for the construction of country houses, timber buildings, frame houses, as well as outbuildings, bathhouses, barns, etc. For brick houses, large cottages made of foam concrete and aerated concrete blocks, a shallow foundation is not suitable. For such buildings, an excellent option would be a combined foundation on piles, for example, a shallow pile-strip type on bored supports.
It is advisable to build a foundation of this type on slightly heaving and non-heaving soils. The ideal option is sandy and sandy loam soils with low moisture content. The groundwater level must be at least 0.5 m below the laying depth. On clay, the construction of an MZLF is accompanied by difficulties, because Most clayey soils are classified as medium- and high-heaving soils. We will consider the features of constructing a foundation with a shallow laying depth on heaving soils below.
The advantages of this type of base include
- economical, concrete consumption is 30% lower than when constructing a conventional recessed strip foundation or a foundation with a monolithic floor slab;
- ease of construction, you can build it yourself without the involvement of workers and special equipment;
- small amount of excavation work - a narrow trench with a depth of no more than 0.7 m is dug;
- small area of contact between the structure and the ground.
Among the disadvantages of MZLF they note
- pouring is carried out at stable temperatures above +10 C;
- limited use due to low load-bearing capacity
- construction is possible only on a flat surface with a slope of no more than 5 degrees;
- lack of a basement in the house.
Expert opinion
Sergey Fedorov
Ask a question to an expertIf you are planning to build an MZLF foundation and “freeze” the construction, then keep in mind that you cannot leave the foundation unloaded during the winter! When the soil freezes, it will push out the monolithic tape, which will lead to a violation of its integrity.
Features of the design of a shallow foundation
A shallow monolithic strip foundation is erected on a flat surface. When building a house on a slope, you will have to combine MZLF with a pile foundation, using supports to level out the height difference. In terms of strength and resistance to deformation, the structure must comply with SNiP 2.03.01-84.
In cross-section, a shallow foundation looks like this:
Features of MZLF that must be taken into account during calculation and construction:
- The depth of the foundation base depends on the depth of soil freezing.
- Be sure to install a cushion made of dry bulk materials: a mixture of coarse sand and gravel.
- When the groundwater level is high, drainage is performed under and around the foundation.
- The base on which the monolithic tape is installed is compacted as much as possible.
- It is necessary to arrange a blind area to drain rainwater and snow.
Taking these features into account, we can conclude that the backfill and blind area are an integral part of the shallow foundation. Requirements for the blind area are specified in SNiP 2.02.01–83.
Calculation of a shallow strip foundation
Calculating the MZLF, which is being built on low- and non-heaving soils, is not difficult. During the calculation, three main parameters are determined:
Laying depth
Determined on the basis of SN “Foundations and Foundations”. The document specifies the following minimum depth values for the foundation base:
- when the soil freezes less than 2 m - 50 cm;
- when the soil freezes to a depth of 3 m - 75 cm;
- when the soil freezes more than 3 m - 100 cm.
For most regions of the middle zone, the depth of the MZLF will be 50 cm. For light buildings, such as a frame barn or a small country house, this parameter can be reduced to 30 cm.
Width of monolithic tape
In order not to make complex calculations, we recommend taking the width of the sole based on the table:
| Wall and ceiling materials | Number of floors | MZLF sole width, m |
| Walls made of lightweight brickwork or aerated concrete with reinforced concrete floors | 1 | 0,6 |
| 2 | 0,8 | |
| 3 | 1,2 | |
| Timber frame walls with timber ceilings | 1 | 0,4 |
| 2 | 0,4 | |
| 3 | 0,6 | |
| Log walls with wooden ceilings | 1 | 0,3 |
| 2 | 0,4 | |
| 3 | 0,6 | |
| Walls made of timber with wooden floors | 1 | 0,2 |
| 2 | 0,3 | |
| 3 | 0,4 |
Height above ground level
The higher the monolithic strip rises above ground level, the better the floors of the house will be protected from dampness and cold. However, the height of the foundation to maintain stability and load-bearing capacity must correlate with its width. The best option: the height of the tape above the zero mark is equal to its width.
Expert opinion
Sergey Fedorov
Professional builder. 18 years of experience
Ask a question to an expertExample: The laying depth is 50 cm. The width of the monolithic tape according to the table is 30 cm. This means that the height above ground level will be 30 cm, and the height of the entire monolithic tape will be 80 cm. The height of the ground part of the MZLF should not be lower than the snow level. The snow depth value depends on the region (you can find it on the Internet). For regions of the middle zone, this value does not exceed 8-10 cm.
Calculation of MZLF on heaving soils
When building a house on heaving soils, more complex calculations are performed, the purpose of which is to determine the heaving deformation. It is quite difficult to make such a calculation yourself, so you need to entrust it to professional designers or use a ready-made table:
| Name and degree of soil heaving | Number of floors of the building | Width of foundation base b, m | Thickness of the pillow t, m | Foundation design option | Reinforcement option |
| clays, loams and sandy loams, fine and silty sands, moist - medium sandy | 1 | 0,3 / 0,2 | 0,6/0,7 | G. | 3 |
| 2 | 0,3 / 0,2 | 0,5 / 0,6 | G. | 3 | |
| 3 | 0,3 / 0,2 | 0,4 / 0,5 | G. | 3 | |
| clays, loams and sandy loams, fine and dusty sands, moist - highly heaving | 1 | 0,3 / 0,2 | 0,7 / 0,8 | G. | 4 |
| 2 | 0,3 / 0,2 | 0,6 / 0,7 | G. | 4 | |
| 3 | 0,3 / 0,2 | 0,5 / 0,6 | G. | 4 |
In column 2 “Sole width” and column 3 “Cushion thickness”, the values for heated and unheated rooms are indicated through the sign /. The column “Reinforcement option” indicates the minimum number of reinforcing bars that must be used to reinforce the monolithic strip.
Construction of a shallow foundation: construction technology
The technology for constructing MZLF is not complicated; filling can be carried out according to SNiPs 3.03.01-87, 2.02.01-83 or according to our instructions. The foundation for a frame house 10 x 10 m can be poured in 1-2 days. Before you start pouring, you need to decide where you will take the concrete solution. There are two options:
- 1order concrete class B22.5...B17.5 at the nearest RBU. In this case, the mixture will be delivered to you at the specified time by a concrete mixer truck. If the ABS cannot reach the pouring site, then a special hose is used through which the concrete solution will be supplied to the formwork. Ordering a sleeve will slightly increase the cost of ABS services. In addition, you will have to pay for every hour of downtime of the special vehicle.
- 2 prepare concrete yourself. At the same time, you will not depend on RBU and will spend significantly less money, however, the quality of the concrete mixture will be slightly lower. When mixing concrete, the recipe must be strictly followed. To prevent concrete from starting to set ahead of time, you can use special additives. You can begin preparing concrete immediately after installing the formwork.
Installation of MZLF: step-by-step instructions from A to Z
Preparatory work and marking
The installation of a shallow foundation begins with site preparation, which consists of removing debris and uprooting stumps. The top layer of soil with vegetation is cut off. If necessary, leveling and filling of soil is carried out, followed by compaction.
The marking is carried out as follows: the perimeter of the future foundation is established, beacon pegs are driven into the corners. Ropes are stretched along the future monolithic tape.
Expert opinion
Sergey Fedorov
Professional builder. 18 years of experience
Ask a question to an expertThe diagonal between the corners must be strictly 45 degrees. You can check the evenness of the markings using a tape measure and a building level.
Construction of trenches and cushions
The depth of the trench depends on the depth of the foundation and the thickness of the cushion. The width of the trench is made 10 cm wider than the calculated thickness of the monolithic tape. This is necessary for installing the formwork. When constructing MZLF on loose soils, the trench slopes can be strengthened with boards. Pillowing is necessary to reduce the impact of frost heaving forces on the foundation. The thickness of the cushion, as a rule, is 20-30 cm for slightly heaving and non-heaving soils. For heaving ones - determined according to the table given above.
For corners where the walls of the future house intersect, it is necessary to strengthen the reinforcement frame by installing additional vertical rods, which are welded to the longitudinal rods. This reinforcement allows the strip foundation to withstand critical loads acting at the intersections of the walls.
You can lay the reinforced frame on a prepared cushion, but it is better to do it on the starting layer of concrete. The thickness of the starting fill should not exceed 20% of the entire height of the tape. Concrete pouring helps create a more even surface on which the reinforced frame is laid. If you decide not to fill the starting layer, then support fungi should be used to raise the reinforced frame above the surface of the pillow by 5-7 cm.
Expert opinion
Sergey Fedorov
Professional builder. 18 years of experience
Ask a question to an expertThe reinforced frame should be located in space, nowhere in contact with the bedding and formwork.
Pouring concrete
Filling should be done at a temperature of +10 C and above. Before pouring, the formwork must be moistened, then the concrete will lie more evenly. The mixture must be poured in layers, the layer thickness should not exceed 40 cm, optimally 20-30 cm. Each layer is subjected to 5-10 minutes of vibration compaction. This technology does not allow voids to form inside the concrete. To supply the concrete mixture to the formwork, you must use an elastic sleeve or chute.
Layer-by-layer foundation pouring
After pouring is completed, the formwork is covered with a vapor-proof film. Hardening of the concrete lasts 25-30 days, after which the formwork is dismantled and the gaps between the foundation and the trenches are filled with soil.
Insulation of a shallow foundation
Professional builders recommend be sure to insulate the MZLF. It is recommended to do this immediately at the time of construction of the structure. An insulated foundation will protect the floors of the house from dampness and cold, which is especially important when arranging the floor “on the ground”. In this case, in the absence of thermal insulation, all the heat from the floor will go into the ground.
There are external and internal thermal insulation MZLF. External - when the insulation is attached to the outside of the monolithic tape, internal - from the inside. External insulation is considered mandatory, but internal insulation is usually done if the house has a basement. What insulation should I use? There are a lot of options. The most popular are:
- Penoplex. Dense thermal insulation, excellent heat conservation. Its service life is significantly longer than that of conventional foam. Penoplex is resistant to rodents, mold and practically does not absorb moisture. In terms of price/quality ratio, this is the best material for thermal insulation of a shallow foundation.
- Expanded polystyrene. The extruded material is slightly inferior to penoplex in terms of physical and mechanical properties. However, the price of polystyrene foam boards is 20-30% cheaper. It can be used in dry and dusty soils with minimal moisture.
- Polyurethane foam. Liquid spray thermal insulation is an expensive option, but it has many advantages: no joints between slabs, a service life of at least 50 years, minimal water absorption and resistance to aggressive environments.
It is not recommended to make a prefabricated foundation on heaving soils. The forces of frost heaving will push out individual elements, which will lead to the destruction of the foundation.
If all work on the installation of FBS is carried out correctly, a small prefabricated foundation will last 70-80 years. This is exactly the service life that reinforced concrete blocks have.
Description
Already based on the name, you can understand that this type of foundation will be somewhat reminiscent of a tape under the outline of the building.
Like other types of foundation, it can be:
- monolithic - poured entirely immediately at the construction site;
- prefabricated - consist of individual factory-made elements (foundation blocks and slabs, bricks for small buildings, in mining areas -).
Specifications
It is a closed loop for load-bearing and self-supporting walls of buildings and structures. The width of this tape is slightly greater than the planned thickness of the walls.
Must be buried in soil with a sufficiently strong load-bearing capacity, because transfers only vertical load to the underlying soil, unlike, say, hanging piles, which provide bearing capacity due to lateral friction forces.
Necessary building materials
In the case of a prefabricated type, you will need the foundation elements themselves - foundation blocks and foundation pads, as well as cement mortar to connect the fragments into a solid object.
For the monolithic version you will need . It can be removable or remain in the body of the foundation, further strengthening and waterproofing it. Well, actually for the foundation itself you need reinforcement and concrete mixture.
Advantages and disadvantages
Advantages:
- Allows you to arrange a basement in the building - the side surface of the foundation in this case will play the role of basement walls.
- Relatively economical.
- Suitable for a variety of structures with complex plan shapes, different number of storeys, large and small loads.
- Allows you to make different depths for walls with different loads, which saves materials.
- Requires less excavation work compared to.
Flaws:
- Not suitable for heaving and weak soils.
- Relative to pile and column, it is more material-intensive, labor-intensive, and will cost more.
- Unprofitable in conditions of large depth of soil freezing.
Stages of strip foundation construction
Step-by-step instruction
- Before proceeding directly to the construction of the foundation, it is necessary to determine the depth of its foundation. To do this, it is important to clearly understand what the loads will be from the dead weight of the building, the people and things located there.
- In addition, it is necessary to conduct an analysis of the soil at the construction site, because the bearing capacity depends on its type and other characteristics. A detailed laboratory study would be optimal, but if this is not possible, you should at least determine its type, density, and humidity. The methods of these studies are described in detail in regulatory documents; they do not require complex equipment or special knowledge, i.e. Almost everyone can do it.
- Next, excavation work begins - cutting a trench or pit 30-50 cm deeper than the depth of the foundation. These centimeters will be occupied by a sand or sand-gravel cushion. Its role is to level the bottom of the pit and give the foundation additional hydro- and thermal insulation. The pillow should be properly sealed.
- Also, in some cases, concrete preparation or so-called concrete preparation is poured on top of the cushion. “concrete footing” made of lean concrete (usually B -7.5) 10-15 cm thick.
- If a prefabricated foundation is selected, then you can begin laying the elements. A brick foundation can be laid by hand, but special equipment will be required to work with heavy blocks and slabs.
- The components of the foundation are connected to each other with cement-sand mortar. For strong adhesion, it should not be made too liquid. To make the connection stronger, you can add a thinner reinforcement mesh.
- Blocks laid flat can be used instead.
- The prefabricated strip foundation can be loaded within 1-2 days. However, in comparison with similar ones, it will have about a quarter less strength and will cost 30 percent more.
- The construction of a monolithic foundation begins with the installation of formwork. Already at this stage it is necessary to take care of the holes for laying various communications. In the right places, sections of durable pipes of the required diameter are installed, filled with earth or sand, so that the solution does not subsequently flow into it.
- Next, the reinforcement frame is installed. Individual reinforcement bars are usually connected to each other using binding wire. The use of welding is undesirable in this case, because it significantly reduces the corrosion resistance of reinforcement steel.
- If further construction is also monolithic, then 5-10 cm releases are made at the foundation reinforcement. They will subsequently be connected to the reinforcement of walls or columns.
- It is important that the reinforcement is completely inside the concrete stone, nowhere in contact with the external environment, otherwise corrosion will soon render it unusable. The protective layer should be at least 4-5 cm.
- Nowadays fiberglass reinforcement is becoming quite popular. Its advantages include low weight and price. However, there are significantly more disadvantages - fiberglass is flammable, which means that in the event of a fire, a structure with such reinforcement will collapse much faster and more severely than with traditional steel. Moreover, this material is not resistant to concrete components. To protect it from destruction, a special coating is needed, which impairs the adhesion of concrete to reinforcement. Accordingly, the load-bearing capacity of the structure becomes worse. In addition, the plastic reinforcement bends weakly.
- After installing the reinforcement, the concrete mixture is laid. It can also be produced independently directly at the site under construction. However, the use of ready-mixed concrete is preferable. Manufacturers constantly monitor the quality of the components and the resulting mixture, optimize the compositions, and have the opportunity to use various additives. As a result, you can be sure that the concrete used will meet the requirements of strength, frost resistance, water permeability, etc.
- The strength of concrete is ensured by precise adherence to the proportions of its components - cement, sand, crushed stone and water. In order not to violate these proportions, in hot and dry weather the drying structure must be additionally watered. In damp and rainy conditions, the foundation will have to be covered with plastic film.
- After laying the foundation, it should be protected from moisture in the soil. There are various types of coating, roll, sheet and sprayed waterproofing, which are often combined.
- Along the perimeter of the building, at a slight slope, there must be concrete slabs, paving slabs or other suitable materials. Its role is to remove precipitation from the foundation.
Common mistakes to avoid and their consequences
Excessive haste
If the foundation is monolithic, then it is necessary to allow the concrete stone to gain a significant part of its strength. If hardening accelerators were not added to the mixture, then under normal conditions it will gain almost one hundred percent strength on the 28th day.
Ideally, it is better to wait this time before continuing construction work. If you need to build much faster, then you should wait at least a week. On the 7th day, concrete already has about 75% of its final strength.
Otherwise, the foundation may deform, nullifying all the work on its construction. And it’s good if this happens during the construction stage, and not when residents move into the house.
Ignoring waterproofing
Waterproofing should not be neglected. Even if the construction region has a fairly dry climate, and there is no groundwater near the building, a certain amount of liquid in the soil will be necessary. Through the pores in the concrete stone it will seep into the room, causing dampness and fungus there.
As you know, when water freezes, it expands, so in winter it will literally tear apart the concrete from the inside. If chemically aggressive substances are present in it, the destruction process will accelerate even more.
In a destroyed concrete stone, the reinforcement will quickly become unusable.
Long breaks in concrete pouring
A monolithic foundation should not be poured at intervals of more than 12 hours. Otherwise, the connection between the previously and later filled parts of the structure will be weak, which means the strength of the entire foundation will decrease.
Among other types of foundation, strip foundation is the most common in private construction. Pouring it does not require significant financial costs and is not particularly difficult - even a novice builder can build it, you just need to understand the peculiarities of the work.
Advantages and disadvantages
Like any building structure, a strip foundation has its advantages and disadvantages; it performs well in some operating conditions and is completely inapplicable in others.
To avoid mistakes in the design and construction of buildings based on a strip foundation, it is important to know all its properties and features. So, the main advantages of the design include:
- low cost of raw materials and installation work due to its small size;
- simplicity and ease of installation, no need for complex technological equipment and special professional skills of workers;
- resistance to constant high loads, that is, suitability for private two- or three-story construction;
- compatibility with all modern wall construction technologies;
- high speed of pouring concrete, allowing to significantly reduce construction time.
However, this type of foundation has several disadvantages, the most serious of which are:
- the need for a detailed analysis of the soil and carrying out rather complex design calculations in order to determine the geometric parameters of the future foundation;
- a large mass of the structure, which, if there is an error in the calculations, will contribute to the “subsidence” of the building.
Having analyzed all the pros and cons of a strip foundation, we can come to the conclusion that the optimal area of its application is private construction on fairly strong, stable soils without a slope. In addition, this type of foundation can help out in conditions of a limited budget and with short deadlines for completing work.
Types of strip foundations
The main criterion for classifying strip foundations is their internal structure. Depending on it, designs are divided into three groups:
Pile-and-tape structures are kept apart. They are usually made using monolithic technology, but include, among other things, deep cast piles with a reinforcement cage to support the foundation on unstable soils.
Materials and tools for work
The role of the main building materials used in the construction of formwork, installation of rods and pouring of strip foundations is played by:- boards, including lighthouse, longitudinal and necessary for the manufacture of formwork panels;
- reinforcement bars with a diameter of at least 10 mm are selected in accordance with the design loads and reinforcement pattern;
- wire, tension hooks and staples, which are used to fasten rods;
- concrete mortar, the components of which are cement, sand and crushed stone (the proportions of the components are given in the table below).
The set of tools varies depending on the planned scope of work. If the perimeter and width of the foundation are relatively small, hand tools predominate, such as: - shovels, spades for excavation and pouring;
- metal containers for preparing concrete;
- hammers, saws and other carpentry tools;
- pliers and pliers for working with wire;
- metal cutting tools, for example, a hacksaw, a jigsaw, an angle grinder.
Marking strip foundations and earthworks
Unlike, tape is perfect for the construction of buildings with basements, basements and underground floors. However, on heaving soil this option will be quite expensive - this type of foundation is best erected on dry soil, which heaves less than wet soil. It will also be unprofitable to pour the foundation to a great depth, but for small houses, bathhouses and garages it is best suited.
Since preparing the foundation for construction takes almost a third of the total construction cost, you should figure out in advance how to properly make a strip foundation. You also need to research the type of soil on the site and the depth of its freezing to understand whether this type of foundation is even suitable for you. It will be much more difficult to correct your mistakes later.
Before building a strip foundation, it is necessary to clear the area of excess debris and begin marking it. In accordance with the prepared project for a garage, bathhouse or house, it is necessary to mark the external and internal boundaries of the future foundation on the ground. This is done using available means: wooden pegs or reinforcement rods and rope (wire, strong fishing line).
It is necessary to mark the external and internal boundaries of the future foundation on the ground
How to mark a strip foundation perfectly evenly so that you don’t have to move pegs from place to place:
- start marking by determining the axis of the future building;
- using a plumb line, mark the first corner, and from it, pull a cord or fishing line perpendicularly to the second and third corners of the building;
- then the fourth angle is determined using the square;
- check all the angles by measuring the diagonals - if the angles match, you can drive in pegs and stretch the fishing line between them;
- make the internal markings in the same way, stepping back from the external one by 40 cm (the optimal width of the foundation).
Having finished marking, study the surface differences in the area and select the lowest point. From here you will need to start counting the depth of the trench in order to eliminate future differences in the height of the foundation. For a small house, a pit depth of about 0.4 m will be sufficient.
The pit can be dug with your own shovel or using an excavator. Just don’t dig by eye - be sure to check with a water level to ensure that the bottom of the trench is as level as possible, this precaution will help avoid many problems in the future. Do not forget that the walls of the trench must be strictly vertical.
The pit can be dug with your own shovel or using an excavator
Installation of formwork and reinforcement
A sand cushion is placed at the bottom of the dug trench, which not only reduces the load on the foundation in the off-season, distributing it over the entire base area, but also saves building materials. Pour sand in a layer of at least 150 mm, level its surface using a water level and compact it, moistening it with water. You can pour a layer of crushed stone on top of the sand cushion and lay waterproofing in the form of roofing felt or plastic film to enhance the strength of the base.
Before pouring the strip foundation, you will definitely need to build formwork from available materials - plywood, wooden boards, pieces of metal tiles, etc. The formwork is screwed together with screws or nailed down, with the heads of the nails placed inside to make it easier to disassemble the structure later and the foundation walls to be smoother. The installed formwork should protrude at least 30 cm above the ground surface. Inside the formwork around the entire perimeter, pull the rope at the level to which you will pour the foundation. Immediately take care of the holes for sewer and water pipes, otherwise you will have to cut them later, violating the integrity of the concrete monolith.
The formwork is screwed together with screws or nailed down
The next step will be laying of reinforcement. Tie the reinforcing bars with a cross-section of 12 mm with a special knitting wire so that the sides of the square cells are 30 cm each. It is better not to use welding, since corrosion will appear at the welding points, and knitting with wire also ensures flexibility of the structure when the ground moves. When laying the reinforcement in the trench, make sure that there is a 5 cm gap on all sides, then the reinforcement will be inside the monolith.
Pouring a strip foundation with your own hands
Now let's figure out how to properly fill a strip foundation. Calculate how much concrete you will need by multiplying the height, length and width of the foundation. You can prepare a concrete solution yourself by mixing 3 parts sand, 5 parts crushed stone and one part cement, diluting with water to the optimal consistency. But it is still better to use factory-made concrete, since you will not be able to pour concrete prepared by yourself at one time; as a result, “cold seams” and cold bridges are formed, through which water will subsequently seep, destroying the foundation. If you will be pouring the foundation using a machine, make sure that there is access for pouring from any corner of the formwork, and that the solution in the machine has not had time to harden - dilute it with water if necessary.
Video about pouring a strip foundation
Step-by-step filling instructions:
- concrete is poured little by little, in layers of 20 cm;
- each poured layer is carefully compacted with special wooden tampers to prevent the formation of voids in the monolith;
- for the same purpose it is necessary to tap the walls of the formwork;
- filling is carried out to the level of the fixed rope;
- At the end of the work, the surface of the poured foundation is leveled with a trowel, pierced in several places with reinforcement (so that air can escape), and the formwork is tapped from the outside with a wooden hammer.
Filling is carried out to the level of the fixed rope
So, we figured out how to make a strip foundation, now all that remains is to wait until it dries completely - this may take about a month. At this time, cover the foundation at night with waterproof materials so that rain does not wash away the cement from the surface, and during the day in sunny weather, water it with water to prevent cracking of the top layer. It is recommended to dismantle the formwork no earlier than two weeks after pouring the foundation, and preferably after a month.
Further care of concrete
After pouring, it is important to provide conditions for its uniform hardening, first of all, the necessary temperature and humidity indicators. A set of actions aimed at this is called concrete care.
First of all, you need to cover the foundation, partially isolating it from the effects of solar radiation and other external factors. On cold cloudy days I do this 8-12 hours after pouring, on sunny and windy days - after 2-4 hours. The surface of the concrete is covered with sawdust or sand, covered with burlap or other similar materials. Now you need to ensure a regular supply of moisture, for which the foundation is watered with a hose through a sprayer every 1.5-3 hours, depending on the weather during the daytime and at least twice during the night. Note! If the temperature drops below +5 degrees, humidification will have to be stopped. In this case, special varnishes and emulsions will help retain moisture.The maintenance period depends on the brand of cement used. For fast-hardening varieties, 2-3 days are enough; standard cement is moistened within a week, and slow-hardening cement – up to two weeks. In addition, it is necessary to take into account the configuration of the foundation - deep and wide structures require more careful maintenance.
Answers to frequently asked questions
Is it possible to make a basement with a strip foundation?
A strip foundation can be considered the best option for implementing basement or cellar construction projects. It has sufficient depth into the ground to withstand additional loads, provided that the basement is dug at some distance from the load-bearing walls.How to properly make a floor with this type of base?
The floor in buildings with such a foundation is created using the layer cake method. The soil is covered with sand, compacted and covered with crushed stone, a metal cellular screed is placed above it, and a layer of waterproofing is placed on it. Insulation and finishing layers of the floor are laid on top of the waterproofing.
Video on the topic
The video shows the appearance of a strip foundation of complex configuration with permanent formwork.