Among all types of foundations, it is the tape construction that is widely used in private housing construction. When arranging it, the main thing is to avoid mistakes, otherwise the strength of the building will be a big question. Only if the strip foundation technology is followed is it possible to build a reliable and strong house that 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 bars, which are connected into a frame. From a constructive point of view, a tape-type foundation is a monolith that stretches under the bearing walls and nodes of the structure being erected.
There is also a prefabricated structure, but it is used in industrialscales. In private construction, this option is more expensive and requires the involvement of heavy special equipment. In addition, its strength is 25% lower than the monolith.
Since it is not possible to pour 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 ground.
Installing a strip foundation is the best option when building houses in areas where groundwater is quite deep and its level is below the freezing point of the soil. This avoids the arrangement of the drainage system, which requires a large investment in building a house.
If groundwater does not lie deep on the site, then it makes sense to choose a shallow foundation. It is able to withstand seasonal ground movements, including heaving in the event of freezing or thawing.
Application of strip foundation
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, it is possible to draw a conclusion regarding the degree of load of load-bearing structures on the base.
Which houses are strip foundations best suited for? Its application is relevant in the followingcases:
- Bearing walls are heavy, which is typical 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, in the arrangement of the basement, basement or garage.
The strip foundation is especially good for areas with heterogeneous soil. This allows you to even out the load on the base. The ability of the base to withstand high pressure allows it to be used for the construction of residential buildings, summer kitchens, bathhouses, outbuildings, garages and other garden structures.
Strengths and weaknesses of the strip base
The widespread use of such a basis is largely determined by its main advantages.
Among the main advantages of strip foundation technology, the following advantages can be distinguished:
- Versatility - buildings of any number of storeys can be built on such a foundation.
- Easy 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 a reinforced concrete tape can be up to 150 years, because external factors have the most minimal effect on such a foundationimpact.
As for the disadvantages, they include increased consumption of materials and labor costs. The economic component in the construction of any house is far from the last thing that people pay attention to. This design should be preferred in cases where it is impossible to do without this option.
Varieties of strip 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:
- shallow (MZLF);
The surface base is preferred in the case of the construction of greenhouses, fences, garages, as well as other outbuildings with low weight.
Shallow foundation is suitable for the construction of frame structures, as well as when used in the construction of wood and foam concrete. Ideal for areas with uniform or slightly moving ground. The immersion depth can vary from 500 to 700 mm. At the same time, the cost of this type of strip foundation is lower than that of other analogues.
Recessed pulling belt is a classic design that fully meets the requirements in the case of construction of heavy objects. This is the best option for areas where the ground is mobile. The depth of the foundation arrangement 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 cushion, after which a layer of waterproofing material should be laid. This measure avoids erosion under the influence of groundwater. However, when building a garage or a country house, this stage can be skipped, which cannot be said about the construction of a whole house, and more than one floor.
The strip foundation technology uses its own terms for convenience. The upper part, where the above-ground supporting structure will be placed, is called the "cut-off". The lower part is called the "sole". Consider the technology for arranging a strip foundation of a monolithic type made of reinforced concrete. The whole process can be conditionally divided into several stages:
- digging a trench;
- formwork installation;
- reinforcement procedure;
- pouring concrete mass;
- concrete care;
- removing formwork.
Let's consider each of them separately.
The first step is to prepare the site for the arrangement of the foundation. To do this, you should clean it of debris and everything that will interfere. Green spaces, tree stumps, large stones - all this will not allow starting work on arranging the foundation for future construction.
Next, the level of groundwater should be drawn, as well as the type of soil at the border of the sole of the base. This work must be assignedspecialists. 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 fine for this, but lime mortar can also be used.
The marking should start from the corner and then go parallel to the fence or the road for a distance equal to the length of the house. Then the rest of the sides are marked. In this case, you should check the evenness of the corners, for which you need a building level. The correctness of rectangular outlines is checked by measuring the diagonals - they must be equal to each other. Permissible error - no more than 20 mm.
To build a tape monolith, you will need the following materials:
- Boards or polystyrene foam - for the construction of formwork.
- Reinforcement is needed to assemble the frame and connecting elements.
- Concrete is actually the foundation material itself.
- Waterproofing materials - understand 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 choice and calculation of concrete for a strip foundation. To do this, it is necessary to take into account the load exerted by the erected building, as well as climatic, soil and other conditions under which the planned operation of the planned structure is planned.
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 frozen mass is able to withstand a weight of up to 200 kg/cm².
- Frost resistance - F100. This indicates that concrete will endure 100 freeze and thaw cycles.
- Presence of waterproof W.
If it is necessary to build a heavier building, and taking into account the chemical aggressiveness of the soil and other factors, concrete with higher strength and density should be chosen. A good option in this case is to include sulfate-resistant Portland cement.
The next stage of arranging the strip foundation 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 dig a foundation pit. Work can be carried out manually or using an excavator. However, even if you involve construction equipment, you still have to work with a shovel in order to align the edges of the trench.
At the same time, if the project provides for digging a foundation pit, then mechanical force is definitely indispensable. But the trenches themselves are quite capable of digging anyone. Then the bottom must be well cleaned in order to prepare for the next stage. Now you can proceed to the arrangement of the pillow. Its thickness depends on the type of soil:
- If there is normal soil on the site, 100 mm is enough.
- In the case of subsidence, swelling or heaving soil, the thickness should be increased to 400-500 mm. In thatIn this case, the pillow acts as a damper, which allows you to compensate for stress due to ground movements, uneven subsidence, including an increase in volume.
The technology of the strip foundation device provides for the layer-by-layer formation of a pillow of 150 mm with careful tamping. Finally, it remains to lay a layer of waterproofing material.
The installation of a strip foundation cannot be done without formwork, which can be of different types depending on the material used:
- Removable. This type of construction is used most often, and it is relevant not only for the construction of the foundation, it has different applications in the construction industry. The main material is wooden planks.
- Fixed. Most often made from polystyrene foam. At the same time, the peculiarity of such formwork is that in this case heat and waterproofing is immediately provided.
The structure must be placed in strict accordance with the markup, and it must rise 100 mm above the level of the foundation. For stability to the formwork, supports are adjacent, both from the outside and from the inside. A polyethylene film is laid inside the entire structure created 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. A regular marker, which is clearly visible on the tree, will do. The use of a hydraulic level will ensureuniform pouring of concrete.
What strip foundation reinforcement should I use? The answer will be given a little later, but for now let's consider what the essence of the use of these rods is. The need for reinforcement is due to the multidirectional impact on the foundation:
- Direction down from the mass of the structure above the structure located above.
- Directed upwards due to soil swelling or frost heaving.
- Stress due to uneven subsidence resulting in bending.
All this ends with the fact that the foundation begins to function as a monolithic beam, capable of bending in different directions. As a result, stretched zones are formed in the cross section. Accordingly, the strip foundation is akin to a system of such beams, which are located on an elastic foundation.
Concrete withstands compressive loads well, but cracks when stretched. In this regard, a monolithic tape structure must be reinforced with meshes and spatial frames. The metal rods will just absorb the tensile forces, protecting the hardened cement mass from cracking.
Previously, it was considered which concrete for the strip foundation is most suitable, but the reinforcement process itself plays an important role. Making a frame requires three types of reinforcement:
- longitudinal working reinforcement with a diameter of 12 mm or more;
- horizontal clamps of 6 mm or more;
- vertical clamps - from 8 millimeters.
The rods should be connected with a knitting wire, since the welded joint has a low strength, and reliability leaves much to be desired. In order to make work easier and faster, it is best to use a knitting gun.
Before buying reinforcement, you need to calculate its quantity to form a reinforcing frame. It is also 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 step 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 gap between the surface of the frame or grid and the walls of the formwork.
It is believed that a brick strip foundation lasts much longer than a concrete strip. However, such a foundation requires special preparation and therefore, basically, it is a monolithic strip structure made of concrete that is preferred.
But back to our topic: it is the turn to pour the concrete solution into the prepared formwork. Here you should use the same principle as in the case of the formation of a sand cushion - in layers of 150-200 mm. 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 wallsformwork.
The concrete mass itself for the formation of the floor of the strip foundation must be of a homogeneous consistency, division into layers is unacceptable! Filling should take place at a temperature of 20 ° C, otherwise (if in winter) it is necessary to add antifreeze compounds to the mixture, as well as ensure its heating during manufacture and transportation.
It is necessary to follow certain rules:
- It is permissible to drop the concrete mass from a height of no more than 2 meters.
- Concrete compaction is best done with a vibrator or bayonet.
- Concrete should be drained from different points, which will reduce the process time and avoid stretching the mortar, which reduces its properties.
- It is advisable to fill in one day with breaks up to 2 hours no more.
If concrete must be poured from a height of more than 1.5 meters, portable chutes or similar devices should be used.
After 10 days have passed after pouring concrete into the formwork, it's time to start processing the outer walls of the base using bituminous mastic. A waterproofing material (roofing material) is laid on top.
After some time, you should check the waterproofing and, if defects are found (peeling, cracks, etc.), eliminate them. If this is not done, then the final cost of the strip foundation may increase several times due to its own negligence.
At the final stage, it is necessary to form an annular drainage system. After that followsfilling the formed sinuses with sand of medium grain size, which in turn must be carefully compacted, for which it should be periodically watered with water.
This procedure is done manually, taking care of 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. A monolithic concrete structure gains its strength 28 days after pouring.
Floors on the ground in a strip foundation
This is the most common option, which is preferred in the case of the formation of a strip foundation. Its huge popularity is due to a number of advantages. Moreover, its arrangement does not require the involvement of heavy equipment and expensive materials. But what does flooring on the ground mean, and in what cases is it done?
Usually, the ground under the flooring does not freeze through, but is saturated with moisture. In this regard, ventilation holes are formed in the basement of the house, which are not closed even in winter. At the same time, in the course of creating a ventilated space, it is permissible to use any kind of heat-insulating material. But if the plinth is too low, then there is no room for ventilation. Under these circumstances, a floor is created on the ground.
This flooring design completely eliminates the space between the ground and the floor itself, since it is located on the ground itself. This eliminates the formation of an air gap. That is, it is poured between the wallsbasis.
In most cases, it is the floors on the ground in the strip foundation that are preferred, and therefore it does not perform load-bearing functions. It is the concrete tape that will take the weight of the load-bearing walls and roof. On the floor, there is a load from the objects placed on it (including internal partitions) and people. In its structure, such a floor is multi-layered:
- litter layer;
- layer of waterproofing material;
- insulation layer;
- main bearing surface;
- leveling screed;
Selecting the material for each layer will not be difficult, since they are easy to find, and the cost is low.
How much can the arrangement of a strip foundation cost, at least approximately? If on a turnkey basis, then from 60,000 rubles, but two main factors should be taken into account here - the work and the materials used. The dimensions of the building itself play an important role, because arranging the foundation for a cottage two-story high (10x10 m) will cost more than building a one-story building 8x8 m in size or a half-brick summer cottage 6x6 m.
The price of a cube of concrete (from 4450 rubles) is also taken into account, since the preparation of the working mixture is also an important step. You can buy a ready-made composition or make your own efforts. In the latter case, you can reduce costs by 15-20%. However, it is worth considering the rental of a concrete mixer (it is not advisable to purchase it), as well as ensuring its uninterrupted functioning: pouringmust be carried out continuously, otherwise the tape will not be solid.
As for the reinforcement, here one should not save on rods, since such a rash step leads to a decrease in the strength of the frame, and therefore, of the base itself. In the absence of a project, it is recommended to take into account such a calculation - 10 linear meters per square meter of foundation area.
As a conclusion
Arrangement of the foundation is a crucial stage in the construction of a building. The durability and efficiency of operation of the entire structure depends on its implementation. If mistakes are made, it 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 get down to business, and 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.