When building a house, special attention is always paid to the foundation. And it is not surprising: the correctness of the design made depends on how long the house will stand, how quickly damage will appear in its walls, and even how warm and dry it will be, because both cold and moisture from the soil are transmitted more strongly than through the air.
Conditions on the site and the design of the house itself may be different. All this should be provided for in the foundation design. If you do not take into account all the specifics and allow miscalculations, this can lead to irreparable consequences, up to those cases when further operation of the house is difficult or even impossible.
Sometimes only a complete replacement or serious reinforcement of existing structures can help. If we estimate how much the foundation for a standing house costs, it becomes clear that this forced measure is still much more profitable than building a new house.
Frightened by reports of the consequences of mistakes in building foundations, people are anxious to look for traces of them in their own homes. And sometimes they find it. Here's what the foundation problems face:
Cracks appear in the outer walls. This is because part of the house begins to sag and the house begins to split along the stress lines.
2. Interior decoration suffers too. Pieces of plaster may fall off, walls may diverge at the joints.
3. Utility pipes entering the house - gas and water pipelines - can bend and deform, up to rupture. And in fact, and in another case, this can lead to an emergency.
4. Due to deformation of the window openings, the sashes of the window frames may not close.
If the windows are constantly closed, the glass units may crack.
5. On floating soils, a house can slide if the type of foundation is chosen incorrectly or if its implementation fails.
6. With a rapid and critical settlement of a part of the foundation, a fragment of a house may collapse.
Perhaps this is the most serious consequence.
It is hardly worth waiting for minor cracks and other signs to lead to a disastrous outcome. You need to think about and calculate how much it costs to reinforce, re-lay or completely replace the foundation with complete preservation of the structure of the house.
Repair work, or a set of measures to replace it, are based on one general principle. The house standing on top is fixed in the position in which it is located.
After that, in the area of the foundation, soil is selected until the defects in the structure are exposed.After that, either reinforcing elements are built, which are then firmly connected with the old ones. Or the old defective foundation is dismantled in parts, and a new one is poured in instead. Depending on the type of foundation, the nature of the work, and therefore their cost, will be different.
The columnar foundation has both pluses and minuses due to the peculiarities of its construction and operation.
It is made widespread by its relatively low price, low material consumption compared to other types, and the relative ease of construction. On the other hand, there were some drawbacks: such a foundation is not intended for heavy houses, heavy loads can deform it.
By the way, excessive load may cause malfunction of the base. Then it will be necessary to completely redo the foundation, changing its type, and this work is quite expensive .
Such a foundation consists of columnar bases, driven or dug into the soil, and a horizontal belt connecting all the protruding ends of the beams along the perimeter.
The height of the belt itself is small, which makes it a more economical option compared to the belt. The pillars themselves can be of a variety of materials: concrete, reinforced concrete slabs, screw piles, stone blocks. The depth of digging in these supporting structures is calculated based on the nature of the soil on which the house stands. The softer and looser they are, the deeper the columnar bases are buried. The same is done if there is a lot of groundwater under the soil.
To replace the pillars, they will have to be completely dug out if they monolithic. It is not possible to pull them out through the top - they sit too firmly, moreover, an overhanging house will prevent them from being pulled out. If the pillars are not monolithic, but consist of bricks or blocks, the matter is easier - the pillars can be broken or disassembled. When pouring new pillars, it will not work to use the hole in the ground as formwork, it will need to be built separately.
The strip foundation is designed for a much higher load than the column foundation.
By changing the thickness of the walls and the depth of the laying in a large direction, it is possible to correlate it with a two- and three-story building made of brick or other heavy materials. In the construction of private houses, it is used most often. Another big plus of the tape structure is the possibility of arranging a basement, both warm and unheated.
The basis of this type are tapes of various materials, which are constructed at the bottom of trenches dug under the foundation. It is possible to install these tapes on a substrate of concrete slabs laid on the bottom of the trenches.
This move almost completely eliminates the subsidence of the foundation under heavy houses and its deformation, since the pressure is evenly distributed on the ground.The material may be different:
A large amount of concrete requires equipment. This is either a concrete mixer for preparing concrete directly on the site of sand, cement and gravel with crushed stone of the required fractions in the appropriate proportion, or calling a construction mixer, where the cost of its delivery to the object is already included in the cost of a cubic meter of concrete.
The strip foundation is also undermined during replacement and repair, and then everything depends on the nature of the damage.
The name of this type speaks for itself - the foundation is a concrete slab, monolithic in nature, which provides all the trump cards of the foundation - excellent adaptability and load-bearing stability when constructing on heaving soils - marshy, peaty, clayey, with a groundwater occurrence close to the surface and the top water that constantly accumulates in the upper soil layers. In conditions of unstable soil, a slab foundation is sometimes the only way to erect a structure without fear that it will "float" or it will be distorted by frosty swelling of the soil. Sometimes such a base is called floating, because, like a raft, it holds the house on the waves of the soil, rising and falling with them.
The technology of laying a slab foundation implies tearing a shallow pit in the soil, where a sand cushion is being built, then waterproofing from soil water is made, and then a reinforcing mesh is knitted. Depending on the thickness, it can provide for two, three, or even more layers of rods.
A solid formwork is being built around. The final stage is concrete pouring. The slab foundation requires the greatest consumption of concrete and reinforcement, you can get by with a concrete mixer only in very small houses, and even then, the pouring will take place in several stages.
The plate version is the most expensive, but also the most reliable. The increased material consumption pays off in strength, durability and predictability.
Pay attention! If your house is on a slab foundation, know that it is almost impossible to replace it, just replace the waterproofing and repair it in places.
The easiest and cheapest way to fix problems with a columnar foundation.Since the connecting belt - the grillage - is not deeply buried in the soil - something rarely happens to it. All the load is transferred through it to the pillars, which are already experiencing transverse or vertical deformation. The replacement of the support is done as follows: a hole is pulled out around the support.
Next to the old pillar, formwork is built with mandatory waterproofing, if reinforcement is inserted into the resulting pipe, and then poured with concrete. The only thing is that the pouring will have to be done by hollowing out a hole in the grillage in order to pump concrete through the extreme upper point of the formwork. If you try to fill the formwork with concrete from the side, it can leak out, and it is inconvenient to do this. If the pillar is built of blocks or bricks, then it can simply be assembled nearby. With a temporary support support, it will even be possible to use old blocks in a new post.
Columnar brick and strip rubble and rubble concrete foundations can be renovated and repaired using gunning . This action can significantly increase the strength of structures, as well as halt the destruction of the old foundation. A special apparatus mixes the prepared dry mixture with water and brings it under pressure through a special nozzle directly to the surface to be treated. The concrete does not just stick to the cleaned surface, but is directly "imprinted" into it, providing excellent adhesion.
The foundation can also be strengthened in this way.
The soil around is selected in such a way as to provide comfortable working conditions at the base of the foundation. There are holes along the bottom edge with a puncher. Reinforcement bars 15 - 20 mm thick are hammered into them. Further, the open trench is filled with rubble up to the pins themselves. Metal beams are laid on them and welded to the reinforcement.
All this is poured with concrete. It serves as an additional belt that strengthens and protects the old foundation.
When the foundation is chipped and destroyed, a concrete jacket is built around it. For this, at a distance of 50 mm from the old foundation, pieces of corrugated reinforcement are driven into the ground. They are tied with wire and poured with concrete over the formwork.
It is also useful to provide connecting elements between the shirt and the old base - this will guarantee the strength. From the inside of the formwork, a layer of waterproofing is laid, for this the cheapest roofing material will come off.
When digging trenches around the house to the full depth of the foundation and replacing old fragments with new, home support required. If we are talking about a complete reform of the foundation, then sometimes the whole house needs to be raised. After the construction of the foundation, the house is lowered onto it and fixed.
At first glance, a sequence of actions that is simple at first glance turns into a very difficult enterprise, because the weight of the house is very large. In addition, brick houses are extremely sensitive to any kind of displacement and can crack easily. For hanging the house, beams are used - wooden beams, if the house is made of logs or beams, and metal I-beams, if you have to lift a heavy brick structure.
For full-bodied brick buildings, jacks are used, each of which is designed for a load of 25 or 30 tons , but in the event of an emergency situation, it can withstand even more. For wooden houses that weigh much less, jacks are used that are designed for a lower load.
There should be at least 4 of them per house from a bar, and they are located in the corners of the building. Special jacks must be used. Automotive vehicles should be used with caution by checking the allowable weight markings on the body.
In order to bring the beams under the house, from two trenches are dug on its sides, and when the old foundation is exposed, a sample is made in it along the entire length of the wall. It is convenient to use a jackhammer for this purpose.
Beams are introduced into the formed channels in such a way as to protrude outside the house by 0.5 - 1 m . Jacks will be placed under these ends.
Important! Lifting a heavy two-story brick house on jacks is a very responsible business. If raised incorrectly, the house may partially collapse.
Working under a raised house is classified as dangerous; it is better to entrust it to specialists who provide safety supports in case of jack breakage.
The technique of lifting the structure is as follows. The ascent begins from the lowest side, which is located along the hydro level. The sagging corner of the house rises 5 - 10 mm from the previous point. After this, the rest of the points are gradually raised.
The jacks are raised in turn, walking around the house. Diagonal devices should not be brought to a height at the same time - you can provoke deformation.
The foundation for a standing house should be calculated individually, depending on the amount of work that is required to return it to working condition. Of course, it is one thing to build an additional rubble concrete "anchor" from the corner to prevent the foundation from slipping, quite another thing is to completely replace the base under the house.
To calculate the maximum costs and for complex jobs, you can use the online foundation cost calculator, which can be easily found on construction sites.
The parameters entered into the calculator need to be obtained by carefully measuring your home. To do this, you will need a 10 m tape measure and preferably an assistant. But you can take measurements alone.
Step 1. Measure the future length of the foundation tape.
For this, the measurement must be made on the outer wall of the house. The results obtained are the length and width of the structure. If the house has an irregular shape, add up the resulting segments - this will not affect the length of the line.
Step 2. Determine the width of the foundation .
.. It should be at least equal to the width of the bearing walls. But if the house is made of heavy materials - brick, cinder block, has more than one floor - it is better to make it 10 - 20 cm wider than the walls . This will cost more, but will reduce ground pressure.
Step 3. Third parameter - the depth at which the foundation is laid. It often happens that problems with the existing foundation arise due to insufficient depth of the laying. The forces of frost heaving bend the foundation, and concrete does not work well for bending - and cracks, and cracks follow along the walls. In central Russia, the laying depth should be at least 1 m .
Depending on the hydrogeological situation, it can be much higher.
If your area has severe temperature conditions, be sure to consider than to insulate the foundation of the house outside.
Step 4. Decide if you need foundation crosshairs under the house itself. Heavy furniture, fireplace, stove without fail require a foundation not only around the perimeter, but also inside the rectangle, under the inner walls.
As an example, for simplicity, let's decide how much a strip foundation for a house costs 10 by 10 meters.
Let's enter the initial data into the calculator, taking the width foundation tape for 500 mm , and height - for 1000 mm . We will choose the average grade of concrete - M300 , although experts recommend taking it higher. As a result, we get the following parameters.
235 kg / cm2.
According to SNiPs, the minimum possible reinforcement structure is the connection of the upper and lower chords, each with 3 rods, vertical rods. Shorter rods run across - the so-called "clamps". A soft knitting wire is used to fasten the rods together. The parameters are as follows:
At the same time, the volume of formwork is very small, only 1.6 cubic meters . This will happen if you take a thin board 20 mm .
But at the same time, the step of installing the supports will be only 16 cm. Let the norms provide for a margin, we will take a step of 20 cm . It's very common anyway. Therefore, of course, it is better to choose a board thickness 30 - 40 mm . Then the volume will grow one and a half to two times, but such a formwork will be excellent to hold.
To save on this parameter will be helped by the fact that the quality of the boards is absolutely unimportant for the formwork, as long as they retain some kind of strength.
We have received an approximate total amount of material that we will need. Let's take the average price for wood, reinforcement and concrete to calculate the cost.
The cost of a cube of concrete in Moscow and the Moscow region is approximately 3200 rubles . per cubic meter of M300 grade with gravel filler.
Accordingly, the total cost excluding delivery will be about 60 thousand rubles, with delivery - at least 5000 rubles more.
When calculating reinforcement, let's estimate the weight for rods with a diameter of 14 mm. This will be more expensive than the real need, but will give a small margin. The price of about 25,000 rubles per ton of rods with a length of 11.7 meters is considered low.
Rounding off, we get about 13,000 rubles for everything.
We will still calculate the formwork with a thickness of 30 mm, this will give us 2.4 cubes. You do not need to buy a high-quality formwork board, unedged second grade will also go, but it costs about 3200 rubles per cube . We get 7700 rubles for the formwork, provided that we buy it and despite the fact that we did not calculate the racks with which it will be strengthened, and about 1500 rubles will go for a 30 by 40 mm bar.
Taking into account the additional costs within each position, you can present the data in the table:
Table 1. Cost calculation ...
|Total||87,000 - 90,000|
To this amount must be added the cost of the work on tearing off the trenches, the possible dismantling of the old foundation.
If we take these parameters into account, we can safely round the resulting figure to 100 thousand , and then multiply it in half (the classic construction contract involves equalizing the cost of work and the cost of materials). Therefore, according to the most conservative estimates, a strip foundation for a standing house will cost about 200 thousand rubles .
The amount of 200 thousand rubles for the foundation is not large by construction standards. But we are talking primarily about a home from scratch. And an already standing house can have a different state.
If it is in good condition, or at least residential and well preserved, then our approximate estimate speaks of the benefits of renovating the foundation. If the house is dilapidated, and you will have to invest a significant amount in its repair, it is better to invest even such an amount as 200 thousand rubles in the purchase or construction of a new house, although this will certainly be much more expensive.
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