Due to the lack of a scheduled preventive repair for a long time or under the influence of high loads, the destruction of the foundation begins. If the walls are strong enough, then the owners of the house decide to repair the base with their own hands. This makes it possible to extend its operational terms and save money.
The foundation of a private house is strengthened by several methods, most of which do not need specialized knowledge and technical capabilities. Professional builders need to be involved only in some difficult cases.
Features and preparation
The foundation should be strengthened in two cases: when signs of structural deformation are detected and if floors are planned to be added. Before starting work, it is necessary to carefully analyze the condition of the house, assess the degree of destruction of the foundation or the likelihood of damage in the near future, and only after that begin the strengthening work.
Establishment of the reasons
As a rule, professionals with specialized equipment are invited to identify defects. But you can carry out the work yourself if you correctly evaluate all the reasons and follow the step-by-step guide on increasing the strength of the foundation. In no case, when identifying defects can not be ignored, otherwise in the future, the inevitable replacement of the foundation will be very expensive.
The primary stages of destruction can be determined by several obvious or hidden signs.
Obvious signs are easy to notice with the naked eye, these include:
- deformed areas on the floor surface;
- change in soil level and the formation of dips around the basement;
- the appearance of defects on the outer lining of the house or its destruction;
- occurrence of cracks in the base and walls;
- minor local damage in the structure itself and on the adjacent site.
With invisible defects, it’s more difficult; special equipment is needed here. Nevertheless, if at least something worries you, for example, peeling of a part of decorative plaster on a basement or facade has occurred or the soil around the house has slightly sagged, invite specialists. Thus, you protect yourself from more serious consequences. Specialists will quickly determine the cause and advise on ways to eliminate it. And you can fix the problem yourself if you wish.
There are a large number of reasons for the destruction of the foundation of the house.
The main ones are:
- initially incorrect calculation of the load on the base;
- large-scale earthworks nearby;
- violation of the technology of construction of the foundation;
- soil freezing;
- poor quality of the base waterproofing or its absence;
- excessive savings in construction, for example, the use of low-quality building materials;
- change in soil properties since the construction of the building;
- constant vibrations (the house is located near the railway);
- improper operation of the structure (lack of heating in winter);
- increased pressure on the foundation due to redevelopment of the house or its reconstruction;
- missing or improperly made drainage.
In addition to all of the above, the environmental impact is affected: minor underground fluctuations, sudden warming, temperature fluctuations, very long rains and a lot of snow. As a result of this, the groundwater level rises and soil heaving processes begin.
In any case, it is impossible to predict all the disastrous consequences of natural collapses, but it is necessary to calculate the risks at the design stage of the house.
What will be the strengthening of the foundation, to a greater extent depends on the type of soil. What soil prevails on the site, it is necessary to determine the first thing.
It is also necessary to carry out a number of research procedures that will help determine the characteristics of the work:
- First, it is worth examining the old foundation - the design, the depth, the materials used.
- Then perform an elevated examination. It makes it possible to establish the load on the foundation, to detect distortions and cracks.
Any old foundation only strengthens over time.
Is it worth it to be strengthened, can be determined by the following signs:
- The donkey house is more than the allowed values.
- The load on the foundation has increased.
- Near the building or inside it a source of intense vibrations arose.
To make the foundation of the house properly reinforced with your own hands, it is necessary to establish exactly whether the construction shrinkage has occurred. This is realized quite simply: markers (gypsum beacons) must be placed across each crack formed on the foundation. If during the month they are deformed, you can get to work. The ways to strengthen the foundations are quite diverse, so they should be divided into several groups.
The final phase of the preparatory work is the unloading of the foundation, which can be either partial or complete. This is an important stage, which does not allow distortions during the strengthening work. Partial unloading. It is carried out by installing temporary supports made of wood, as well as metal and wooden struts.
To begin with, on the ground floor or in the basement, support pillows are laid at a distance of 1.5-2 m from the wall, a support beam is placed on them, and racks are fixed, which then need to be connected with a beam with an overlap and using wedges with a supporting beam.
For the complete unloading of the base, the installation of random beams (metal beam-strapping) will be required. Under the poking row of the brickwork of the wall from each of the two sides, punctures are made, into which it is necessary to place a random beam every two meters and tie them together using bolts (20-25 mm). Places where the randballs are connected to each other must be welded with overlays, and the distance from the wall to the randballs should be filled with a solution of cement and sand.
In the lower part of the wall, near the upper edge of the foundation, through holes are punched through 2-3 m, into which the transverse beams are inserted. Two support pillows are arranged under each transverse beam. The base under the pillows should be sealed.
Before starting the development of the foundation reinforcement project, it is necessary to carry out a technical survey of the structure, which, among other things, should include an analysis of the reasons explaining the inadequate bearing capacity of the foundation and foundation soil. Technical inspection is carried out comprehensively. Any survey begins with a review of the existing design and executive documents relating to both the building itself and the territory in which it is located.
The verification of the house itself (both aboveground and underground parts) includes:
- determination of the mutual arrangement of the main load-bearing structures of the structural elements;
- measurement work;
- technical inspection of structures, including the foundation;
- establishment of physical and mechanical characteristics of materials of structures and soil;
- establishment of planned and actual loads;
- detection of defects and the reasons for their appearance (for example, the foundation burst and a crack went along the wall).
Additionally, for the sake of completeness at the pre-design stage, the results of deformation and geodetic monitoring may be required.
The main types and methods
The foundation can be strengthened by various methods, depending on the degree of destruction of the base, material and many other factors. In addition, the cause of structural destruction is of no small importance.
The foundation is protected from weathering during chemical and physical weathering of the foundation material, when the masonry is affected by surface weathering processes and there are no through cracks in the foundation. As a rule, this happens if the foundation is made of brick or rubble masonry, which has low strength and water resistance.
Chemical weathering can occur when the cement or substance added to the cementitious mass is not stable enough against aggressive environmental influences.
To restore the foundation surface, gunning (plastering with cement mortar) is used on the cleaned (prepared) side surface of the foundation or gunning on a steel mesh fixed on its side surface.
If the weathering processes have covered the foundation to the full thickness, it is necessary either to cement the masonry, thereby strengthening the existing foundation, or to strengthen the foundation with clips, restoring the bearing capabilities of the foundation.
Strength due to broadening
This method is quite difficult to do with your own hands, but several people are able to solve this problem. The sole is a reinforced concrete pillow that serves as a support for the base. First of all, it is necessary to mark the foundation every 2.5-3 meters, to excavate the soil on the sides of the base and under it.
It is necessary to lay a reinforced screed under the foundation, pour it with a solution that must be distributed evenly, and remove air bubbles. This will require a vibrator for concrete. On the sides, the sole must be raised approximately 15 cm above the base.
Strengthening the foundation with a method such as injection is one of the most innovative methods. Own hands to implement it will not work. To implement this method requires special equipment. The essence of the technology lies in the fact that wells with a diameter of 16-24 cm are drilled from various sides in the foundation at an angle (approximately 45), the diameter is selected depending on the conditions. The depth of the wells varies depending on the characteristics of the soil. For a more reliable reinforcement of the base of the house, it is recommended to drill to hard layers of the soil. After this, the wells are filled with solution.
Drill piles made of reinforcement are placed in wells filled with a solution. A cement mixture or concrete is poured into them under a pressure of 1-3 MPa. This process is called “well testing”.
As a result, the soil is compacted, the size of the pile increases by 5-10%. Saturation of the soil with cement or concrete mortar makes it possible to fill voids and pores, strengthens weak areas. Stiffening, solutions deepen the foundation and contribute to an increase in bearing capacity.
According to shotcrete technology
As a result of using the above method, you get:
- soil strengthening under the house;
- additional reinforcement of the base with reinforced concrete piles.
Strengthening using shotcrete technology is an ideal option to restore the foundation of a brick house. It is extremely difficult to do this kind of work with your own hands, it is better to entrust it to specialists.
If you are convinced that you can cope on your own, then you will need:
- hammer drill;
- installation for applying concrete or mortar (gunite gun);
- cement, gravel and sand;
The foundation is strengthened in 2 stages: initially work is carried out from one side of the base and only a week later they switch to the opposite side. Such a temporary pause makes it possible to maximize the design.
Captured areas must be at least 2.5 m in length. A trench is digging a width of 2 m and a depth of 1.5 m, the masonry freed from the soil is cleaned, and notches of about 1.5 cm depth are applied to it.
You can also apply the laid on frame of reinforcing bars (if you want to increase the number of storeys of the structure).
A solution of concrete is made by mixing cement, sand, gravel and water and, using a shotcrete gun, is applied to the foundation, filling all cracks and crevices. Strengthening by shotcrete technology is one of the optimal reinforcing schemes, because it significantly increases not only the bearing capacity of the base, but also its moisture resistance.
There are circumstances when drilling wells is not feasible due to the properties of the soil, the condition of the house or the prohibition of work, accompanied by vibration and noise. In such situations, pressed piles are practiced. Strengthening the foundation of a brick house can be carried out just with the help of such piles.
The technologies of pressed and bored piles are very similar. The difference is that in our case, piles that are already ready for driving are used, they do not need to be poured with concrete with their own hands.
The use of such pile foundations makes it possible, if necessary, to completely transfer the load to a new foundation.
Strengthening the base of the house with screw piles differs from the application of the piles described above in that after screwing the piles into the soil, it will no longer be possible to adjust its position.
As a result of this, two technologies are used:
- “Bulls” - 2 inclined piles are screwed from different edges of the foundation tape. To make it possible to access from inside the building, you will have to disassemble the floors in places, the tape is crushed by piles and will not sag.
- The classical method of amplification is in the MZLF (shallow- deep strip foundation). Through holes are made with a diamond drill, piles are screwed vertically from both edges (as close as the walls of the house allow), the house is lifted with jacks, a double tee or channel is arranged in the hole, the ends of which are welded to the piles.
With the help of ebbs or clips
According to this technology, the foundation can be strengthened by ebbs, reinforced concrete shirts or clips.
Low tide gain
This reinforcement method is relevant for a foundation made of buta or brick.
- Reinforced concrete castings are used instead of the reinforcement cage. They must be installed from 2 sides and squeezed so that their top does not touch the wall, and the lower segment is opposite.
- Next, you need to fix the structure with jacks and ties, dig trenches with grips up to 2 meters.
- The space between the tides and the wall is poured with a solution.
The method consists in constructing along an obsolete foundation a reinforced concrete or concrete cage, which is connected to the old base by drilling channels in the ground and laying reinforced concrete beams or reinforcement. This significantly increases the bearing capacity of the foundation, also due to the increase in the supporting area, the settlement of the building is reduced. Reinforced concrete clips are divided into widened and vertical structures. In broadened clips, the lower segment extends beyond the boundaries of the main contour of the wall to a distance equal to its thickness.
Reinforced concrete clips are installed in the following order:
- A trench with a width of 2-5 meters and a depth equal to the depth of the foundation is digging along the perimeter of the basement contours.
- The foundation is cleaned of soil, and holes for reinforcing bars are drilled in it in a checkerboard pattern.
- Rods with a diameter of 15 to 20 mm are driven into these holes so that they look 20-25 cm beyond the base walls.
- At the ends of the rods, a double-contour skeleton of reinforcement is constructed, on which sheet metal is fixed by welding, acting as a formwork for pouring with a solution of concrete.
- Inside the formwork, a solution is pumped, after the hardening of which a dug dug around the perimeter is filled with earth.
A reinforced concrete jacket reinforcement method is also used. Only the encirclement area of the foundation differs from the clip: the clip closes along the entire outline of the foundation, and the shirt is practiced to strengthen some defective areas.
Strengthening the tape base
The basis of most private houses is the foundation of the tape type. The properties of such bases have the technical ability to locally exceed the loads permitted by the standards. This type of foundation is capable of experiencing local heap of soil. All types of foundations are erected on a bed of rubble stone. When it is upset, it is important to stall this process in time.
To strengthen the strip foundation, a pit is excavated at an angle of 35 degrees in direct proximity to the base. Its depth should reach the level of laying masonry stone. Then a pipe is placed in the dug pit, the diameter of which is 150-200 mm. A pipe is used to pour concrete with a low cement content and a high content of crushed stone or gravel (lean concrete).
Filling continues until the soil is completely saturated. At this stage, all work must be stopped for two hours. During this period, it is necessary to observe the behavior of the soil regarding its saturation with a solution. If the solution begins to go away, then it is necessary to continue filling the pit after a few days. According to practice, absolute saturation of the soil requires a two- or three-fold repetition of the process. Monitoring of the situation is carried out through beacons. In the case of a slight change, their position proceeds to the next step.
A trench 200-350 mm wide is dripped along the contour of the base. On its outer side and at the bottom, a construction of boards similar to formwork is being erected. Reinforcing pins are driven into the base, and a reinforced mesh is fixed to them. A concrete solution is poured into the resulting structure, in which there is a filler from fractions of fine gravel and gravel. Such a construction will significantly strengthen this corner of the house and evenly distribute the loads in a horizontal plane, which will stall the process of settling the house.
The difference between cementation (injection) is that with it, hollow tubes are installed in the base cavity. Typically, this method is used for rubble base, in which there are many voids. The accessibility of the technique is achieved due to the fact that the cavities between the boot and the bricks are filled with cement mortar, and minor cracks are smeared. Hollow tubes are installed so that they extend beyond the cage by more than 40 cm and must be fixed with a solution.
To fill the tube cavities, cement of lesser density is poured into them than for the holder. The work should be carried out in the established order: first you need to make a clip, two days later, when it hardens, you must fill in the tubes placed in advance. Cementation is possible only when the base has retained its bearing capacity.
In those cases when, as a result of weathering and violation of the foundation laying, cracks have formed in the supra-foundation part of the building, the usual filling of open slots with cement mortar may not meet the requirements. Then it is recommended to increase the strength of the structure with other structural measures.
Thinking about the question of how to strengthen the foundation of the house, you need to take into account the following factors:
- The pressure on the foundation of an old wooden house can be reduced by lowering the level of heaving of the soil. To do this, a sand pillow is built under the base, and a clay belt is placed around.
- The mobility of the soil will be significantly reduced if you put a drainage system around. This will increase the density of the soil, thus increasing the strength of the base.
- Basement and foundation insulation will significantly slow down the destruction process and increase the service life.
- Sealing the junction of the blind area will protect the base from precipitation. It is possible to reduce the amount of moisture penetrating into the soil around the foundation by means of a system of gutters located on the roof.
To properly strengthen the foundation, you need to take into account the advice of experienced professionals. They recommend choosing a method of amplification depending on the state of the building, its reconstructive capabilities and the characteristics of the structure. Additionally, it is necessary to keep in mind the state of groundwater.
If the damage is small, and the settlement of the base is completed, then you can limit yourself to repairing the cracks with a cement mortar. With strong shrinkage, it is necessary to eliminate the cause of its appearance. In particular, if the deformation of the foundation was provoked by leaching of the soil, then cement mortar must be pumped into the formed voids. Wells are made at the base of the house and filled with a solution under high pressure. Such a layer excellently strengthens the base and is characterized by waterproofing properties.
To strengthen the shallow tape foundation (MZLF), experts advise using screw, bored or bored injection piles. If there is no technique for drilling and injection, then the work will have to be done manually.
To do this, in problematic areas or around the perimeter of the foundation of the building, they dig up the soil. Fill the ditch with masonry or monolithic concrete. Cracks in the house can be repaired, especially with the help of brick locks, after stabilization of the precipitation process. If the house has not yet sat down, beacons are installed to establish the time for completion of precipitation in places where the house or foundation has cracked.
Each way to strengthen the foundation is developed individually, taking into account the results of inspections and design information. Owners of private housing construction must remember that the strengthening work can be carried out on their own only after a thorough examination, obtaining the results of the examination and all the necessary conclusions.
On how to strengthen the house and avoid cracks, see the next video.