Among all types of foundations, it is the tape structure that is widely used in private housing construction. When arranging it, the main thing is not to make mistakes, otherwise the strength of the building will be a big question. Only in case of compliance with the technology of the device of the strip foundation can a reliable and strong house be built, which will serve faithfully for a very long time.
What is a strip foundation?
In fact, this is a tape of concrete mass, reinforced with metal rods that are connected into a frame. From a structural point of view, the foundation of the tape type is a monolith that stretches under the bearing walls and nodes of the erected structure.
There is also a prefabricated structure, but it finds application on an industrial scale. In private construction, this option is more expensive and requires the use of heavy special equipment. In addition, his strength is 25% lower than the monolith.
Since it is not possible to fill such a scale at a time (the total length of such a tape is considerable), a special technology was developed, the result of which is the production of a monolith from concrete and metal. Due to this, such a one-piece design is characterized by increased strength and reliability, as well as the ability to withstand any load from the soil.
The installation of a strip foundation is the best option when building houses in areas where groundwater is quite deep, and their level is below the freezing point of the soil. This avoids the arrangement of a drainage system, which requires large investments in the construction of a house.
If the groundwater does not lie deep in the area, then it makes sense to choose a shallow foundation. It is able to withstand seasonal soil movements, including its swelling in the event of freezing or thawing.
Foundation footing
The choice of foundation for a particular building depends on several factors - the type of material that will be used in the construction of the facility, the number of storeys of the structure, including various soil characteristics. Taking all these data into account, we can draw a conclusion regarding the degree of load exerted by the load-bearing structures on the base.
For which houses is the strip foundation best suited? Its use is relevant in the following cases:
- The load-bearing walls are heavy, which is characteristic of materials such as brick, concrete, stone.
- In the case of the construction of reinforced concrete or metal floors, which have a lot of weight.
- In areas with heterogeneous soil - as a result, the load on the foundation is distributed unevenly.
- If necessary, the arrangement of the basement, basement or garage.
Especially good is the strip foundation for patches with heterogeneous soil. This allows you to even out the load on the base. The ability of the foundation to withstand high pressure allows it to be used for the construction of residential buildings, summer kitchens, baths, farm buildings, garages and other garden structures.
Strengths and weaknesses of the tape base
The widespread use of such a basis is largely determined by its main advantages.
Among the main advantages of the technology of the device of the strip foundation, the following advantages can be distinguished:
- Versatility - on such a foundation, you can build buildings of any number of storeys.
- Simple installation - the technology itself is easy to implement, and the use of special equipment or a team of builders is not required.
- Strength - perhaps this is the main advantage due to which the foundation is able to withstand loads from load-bearing structures.
- Durability - the service life of reinforced concrete strips can be up to 150 years, because external factors have the most minimal impact on such a foundation.
As for the shortcomings, then they include the increased consumption of materials and labor. The economic component in the construction of any home is far from the last thing they pay attention to. Preference should be given to this design in cases where it is impossible to do without this option.
Varieties of tape base
There are several types of this kind of foundation, depending on the degree of load applied to it. Based on this, the following types are distinguished:
- surface;
- shallow (MZLF);
- buried.
The surface base is preferred in the case of the construction of greenhouses, fences, garages, as well as other outbuildings with low weight.
The shallow foundation is suitable for the construction of frame structures, as well as in the case of use in the construction of wood and foam concrete. Ideal for areas with homogeneous or slightly mobile soil. Depth of immersion can vary from 500 to 700 mm. At the same time, the cost of a strip foundation of this type is lower than that of other analogues.
The recessed broaching tape is a classic design that fully meets the requirements in the case of construction of heavy facilities. This is the best option for terrain where the soil is mobile. The depth of the foundation is determined by complex calculations, which are necessarily included in the project of the house. Usually it is 200-300 mm below the level of soil freezing.
LF device technology
The arrangement of the strip foundation begins with the formation of a sand and gravel pillow, after which a layer of waterproofing material should be laid. This measure avoids erosion under the influence of groundwater. However, during the construction of a garage or a country house, this stage can be skipped, which cannot be said about the construction of a whole house, and not on one floor.
In the technology of the device of the strip foundation for convenience, their own terms are used. The upper part, where the overhead load-bearing structure will be placed, is called the "edge". The lower part is called the “sole”. Consider the technology of equipping a strip foundation of a monolithic type of reinforced concrete. The whole process can be divided into several stages:
- training;
- digging trenches;
- formwork installation;
- reinforcement procedure;
- pouring concrete mass;
- curing;
- formwork removal.
Let's consider each of them separately.
Preparatory stage
The first step is to prepare the site for the arrangement of the foundation. To do this, clean it of debris and all that will interfere. Green spaces, tree stumps, large stones - all this will not allow to begin work on arranging the foundation for future construction.
Next, a groundwater level should be drawn, as well as the type of soil at the border of the base of the base. This work must be entrusted to specialists. After that, the thickness of the strip foundation and the depth of its immersion in the ground are determined. When the geological work is completed, you can proceed to the marking of the site. Stakes and cord are suitable for this, but you can also use lime mortar.
Marking should start from the corner and then go parallel to the fence or the road at a distance equal to the length of the house. Then the other sides are marked. In this case, you should check the evenness of the angles, which will require a building level. The correctness of the rectangular shape is checked by measuring the diagonals - they must be equal to each other. Permissible error - no more than 20 mm.
Materials
For the construction of a tape monolith, the following materials will be needed:
- Boards or expanded polystyrene - for the construction of formwork.
- The fittings are needed to assemble the frame and connecting elements.
- Concrete is the foundation material itself.
- Waterproofing materials - it’s clear why.
In addition, the formation of a pillow is an obligatory step, for which sand or gravel is suitable.
You should also responsibly approach the selection and calculation of concrete on a strip foundation. For this, it is worth taking into account the load exerted by the erected building, as well as climatic, soil and other conditions under which it is planned to operate the planned structure.
In the case of construction of low-rise facilities, it is permissible to use concrete with the following parameters:
- Strength class - B15 or M200. In this case, the solidified mass is able to withstand heaviness up to 200 kg / cm².
- Frost resistance - F100. This indicates that the concrete will withstand 100 cycles of freezing and thawing.
- The presence of water resistance W.
If necessary, build a heavier building, as well as taking into account the chemical aggressiveness of the soil and other factors, you should choose concrete with higher strength and density. A good option in this case is the inclusion of sulfate-resistant Portland cement.
Foundation trench
The next stage of arranging the foundation footing for the house with your own hands (after marking) includes digging a trench according to the marks made earlier under the main load-bearing walls. But if you need a basement or there is a need for a basement, then you should open the foundation pit. Work can be carried out manually or using an excavator. However, even if you use construction equipment, you still have to work with a shovel in order to align the edges of the trench.
Moreover, if the project provides for digging a pit, then you can’t do without mechanical strength. But the trenches themselves are quite capable of being opened to anyone. Then the bottom must be well cleaned in order to prepare for the next step. Now you can proceed to the arrangement of pillows. Its thickness depends on the type of soil:
- If the site is plain soil, 100 mm is enough.
- In the case of subsidence, swelling or heaving soil, the thickness should be increased to 400-500 mm. In this case, the pillow acts as a damper, which allows you to compensate for stress due to movement of the soil, uneven subsidence, including an increase in volume.
The technology of the device of the strip foundation provides for a layer-by-layer formation of a pillow of 150 mm with careful tamping. In conclusion, it remains to lay a layer of waterproofing material.
Formwork Formation
The foundation of the strip foundation cannot be performed without formwork, which can be of different types depending on the material used:
- Removable. This type of structure is used most often, and it is relevant not only for the foundation, in the construction industry it has different applications. The main material is wooden boards.
- Fixed Most often made from polystyrene foam. Moreover, the peculiarity of such formwork is that in this case, heat and waterproofing are immediately provided.
The design should be aligned exactly with the markings, and it should rise 100 mm above the foundation. For resistance to formwork, props are adjacent, both from the outside and from the inside. A plastic film is placed inside the entire created structure in order to avoid the flow of cement mortar.
A mark is made on the inside of the formwork - the limit to which the concrete mass should be poured. An ordinary marker is suitable, which is clearly visible on the tree. Using a hydraulic level will ensure uniform pouring of concrete.
Reinforcement
What kind of reinforcement for strip foundations should I use? The answer will be given a little later, but for now we will consider what is the essence of using these rods. The need for reinforcement is due to multidirectional impact on the foundation:
- Direction down from the mass of the structure above the located structure.
- Upward, due to swelling of the soil or frost heaving.
- The occurrence of stresses due to uneven subsidence, which leads to bending.
All this ends with the fact that the foundation begins to function as a monolithic beam, able to bend in different directions. As a result, elongated zones are formed in the cross section. Accordingly, the strip foundation is akin to a system of such beams that are located on an elastic base.
Concrete withstands compressive loads well, but cracks when stretched. In this regard, a monolithic tape structure must be reinforced with nets and spatial frames. Metal rods will just take tensile forces, protecting the hardened cement mass from cracking.
Previously, it was considered which concrete is suitable for the strip foundation most, but the process of reinforcement itself plays not the last role. Making a frame requires three types of reinforcement:
- longitudinal working reinforcement with a diameter of 12 or more millimeters;
- horizontal clamps measuring 6 or more millimeters;
- vertical clamps - from 8 millimeters.
The rods should be connected with a knitting wire, since the welded joint is characterized by low strength, and reliability leaves much to be desired. In order to make work easier and faster, it is optimal to use a knitting gun.
Before buying reinforcement, it is necessary to calculate its quantity to form a reinforcing frame. Still worth considering a number of its features. In particular, the distance between the clamps should be about 250 mm. At the same time, at the corners, including the joints of the walls, the pitch should be reduced.
In addition to the frame, it is permissible to use a reinforcing mesh - all this is installed in the finished formwork. In this case, it is necessary to observe the design clearance between the surface of the frame or mesh and the walls of the formwork.
Concreting procedure
It is believed that the strip foundation of brick in time lasts much longer than a concrete strip. However, such a foundation requires special preparation and, therefore, mainly a monolithic strip construction made of concrete is preferred.
But back to our topic: it is the turn for pouring concrete mortar into the prepared formwork. Here, the same principle should be used as in the case of the formation of a sand pillow - 150-200 mm in layers. In addition, each layer must be rammed with special wooden devices. This will avoid voids in the concrete mass, the presence of which is undesirable. For this purpose, you can tap the outer walls of the formwork.
The concrete mass itself for the formation of the overlap of the strip foundation must be of a uniform consistency, separation into layers is unacceptable! Filling must take place at a temperature of 20 ° C, otherwise (if in winter) it is necessary to add anti-frost compounds to the mixture, as well as to ensure its heating during manufacture and transportation.
In this case, certain rules must be observed:
- It is permissible to dump concrete mass from a height of not more than 2 meters.
- Concrete compaction is best done using a vibrator or bayonet.
- Concrete should be poured from different points, which will reduce the time of the process and will avoid stretching the solution, which reduces its properties.
- It is advisable to fill in one day with interruptions up to 2 hours no more.
If concrete has to be poured from a height of more than 1.5 meters, portable gutters or other similar devices should be used.
Waterproofing stage
After 10 days have passed after pouring concrete into the formwork, it's time to start processing the outer walls of the base using bitumen mastic. A waterproofing material (roofing material) is laid on top.
After some time, you should check the waterproofing and if defects are found (peeling, crevices, etc.), eliminate them. If this is not done, then the total cost of the strip foundation can increase many times due to own negligence.
At the final stage, it is necessary to form an annular drainage system. After this follows the filling of the formed sinuses with sand of medium grain size, which in turn must be carefully tamped, for which it should be watered periodically with water.
This procedure is done manually, monitoring the safety of the waterproofing layer. If the project of the house includes a basement, then it is permissible to lay insulation on top of the waterproofing material. 28 .
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In most cases, it is the floors on the ground in the strip foundation that are preferred, and therefore it does not perform the supporting functions. It is the concrete tape that will perceive the weight of the bearing walls and roof. The floor also has a load from objects placed on it (including internal partitions) and people. By its structure, such a floor is multilayered:
- sole;
- bedding;
- a layer of waterproofing material;
- insulation layer;
- main bearing surface;
- leveling screed;
- fine coating.
It is not difficult to select material for each layer, since it is not difficult to find them, and the cost is not high.
Issue price
How much can an arrangement of a strip foundation cost, at least approximately? If "turnkey", then from 60 000 rubles, but here it is worth considering two main factors - work and materials used. The dimensions of the building itself play an important role, because the arrangement of the base for a cottage two floors high (10x10 m) will cost more than the construction of a one-story building measuring 8x8 m or a summer cottage 6x6 m in half a brick.
The price of a cube of concrete (from 4450 rubles) is also taken into account, since the preparation of a working mixture is also an important step. You can buy a finished composition or make your own efforts. In the latter case, costs can be reduced by 15-20%. However, it is worth taking into account the rental of a concrete mixer (it is impractical to purchase it), as well as ensuring its uninterrupted operation: pouring must be continuous, otherwise the tape will not become solid.
As for the fittings, you should not save on rods here, since such a reckless step leads to a decrease in the strength of the frame, and, therefore, the base itself. In the absence of a project, it is recommended to take into account such a calculation - 10 p.m. per square meter of foundation area.
In conclusion
The arrangement of the foundation is a crucial stage in the construction of the building. It is on its implementation that the durability and operational efficiency of the entire structure depends. If mistakes are made, this threatens with disappointing consequences up to the collapse of the building and the victims.
For this reason, such responsible work must be approached with understanding. Of course, it is better when real specialists come to work, not only at the implementation stage, but also when creating a project. This will allow you to make all the necessary calculations and the cost of materials (including the price of a cube of concrete), as well as other necessary costs.