Often, owners of private homes are faced with the problem of destroying the foundation. Most often this applies to old log or timber structures. But sometimes strengthening is also required for the foundation of a new house, if during the construction the technologies were not followed and natural factors were taken into account, for example, how deep the soil freezes on the territory. In some cases, the base is destroyed if any objects are built near the house. And, finally, the foundation needs to be strengthened if it is planned to add additional premises to the finished building or build floors. If this is neglected, then an increase in the mass of the building can lead to subsidence, skew of the entrance and window structures, the formation of cracks in the base, and even complete destruction.
The reasons for the partial destruction of the foundation
The foundation is the platform on which the structure is based. It distributes the mass of the building over the entire area and reduces the specific pressure on the soil. The performance and durability of the structure depend on its condition, since it is on the foundation that the entire load from the higher structures falls.
Deep cracks in the foundation indicate the onset of failure
But during the operation of the building, the foundation is often subjected to partial destruction. This may be due to the following reasons:
- the location of the house on an incline, in an earthquake-resistant area or near a railway;
- incorrectly drawn up project;
- errors at the stage of calculating the planned load;
- non-compliance with construction technologies during the construction of the platform;
- the use of low-quality building materials;
- improper arrangement of waterproofing;
- decrease in the quality characteristics of the base;
- natural phenomena - flooding, saturation of the soil with moisture, freezing of the soil;
- human economic activity - improper operation of the house, for example, lack of seasonal heating, construction or laying of communications in the immediate vicinity of the foundation, repair or completion of the house.
Since at the initial stage of construction it is not always possible to accurately predict what kind of load and natural factors the foundation will be exposed to, it will subsequently have to resort to its strengthening. The strengthening of the foundation ensures the reliability and safety of the operation of a private house, since it is suburban households that are most susceptible to natural factors. If you ignore the problem, you may have to completely change the foundation, and it costs a lot of money.
Before starting work on strengthening the foundation, it is necessary to conduct a thorough analysis of the reasons that caused its partial destruction. As a rule, professionals with special equipment are invited for this. They evaluate the factors causing the deformation of the foundation, and give recommendations for their elimination or minimization.
Before strengthening the foundation, its external and internal inspection is carried out. During an external examination, the following parameters are determined:
- dimensions of the building;
- state of supporting structures;
- platform load;
- the presence of cracks and bevels.
In an underground study, indicators are determined:
- device and platform dimensions;
- strength properties of the material used;
- depth of his bookmark.
Before you begin work on strengthening the foundation, you must make sure that its shrinkage is complete. Usually it lasts at least a month. To understand that the shrinkage is over, gypsum beacons are installed across the identified cracks. Their condition will determine when to strengthen the foundation.
At the final stage of preparation for strengthening, the platform is unloaded. It can be full or partial. An important factor is the prevention of distortions that will adversely affect the restoration of the foundation.
To further strengthen the foundation, the building is raised with jacks
Partial unloading of the house platform is carried out using wooden or metal supports and struts.
- In the basement, install supporting pillows, stepping back from the wall 2 m.
- Lay the support bar on top.
- Secure the racks.
- Then use a beam to connect them to the ceiling, and then to the support beam using wedges.
For the complete unloading of the platform, steel beam ties are mounted.
- Under a row of masonry, in which the bricks are laid with short edges to the wall, pierce the gates on both sides, observing a distance of 2 m between them.
- Place the strapping beams in them and secure with 25 mm bolts.
- Using overlays, weld the joining points of the beams, and pour sand-cement mortar between the walls to the beam.
- Punch holes in the lower part of the walls, observing the distance between them no more than 3 m, insert into the holes of the beam.
- Install the cross beams on the pillows on both sides of the wall.
Base reinforcement methods
In modern construction, different techniques are used to strengthen the foundation, due to the rapid development of the building materials market:
- broadening of the sole;
- reinforced concrete pillow;
- cap replacement;
- reinforcing belt;
- reinforced concrete shirt;
- low tide;
- summing up new foundations;
Various methods are used to strengthen the foundation.
Each of these methods has both advantages and disadvantages. Consider the most popular technologies.
In practice, home owners most often resort to the classic, proven method of strengthening the foundation - a method of broadening the soles. The sole is a reinforced concrete pillow on which the foundation rests. This method is the most simple, reliable and relatively inexpensive. Several people with certain skills can handle the job.
- An additional foundation is laid around the house, playing the role of an auxiliary support.
- The sole around the entire perimeter of the structure is fixed at several pre-marked base points, the number of which depends on the size of the building and the degree of destruction of the main foundation. Typically, the distance between the points is 2.5–3 m.
- Excavation is carried out on the sides and under the foundation.
- A reinforcing screed is laid under the foundation and evenly filled with mortar.
- A concrete vibrator removes air bubbles.
- The side walls of the sole rise to the base 15 cm.
The method of reinforcing the foundation by broadening the sole is the simplest, most reliable and relatively inexpensive
Pile foundation reinforcement
There are many varieties of piles with which you can strengthen the foundation.
Additional strength can be added to the construction using bored piles. Recently, this technique has been very popular. But due to the use of innovative technologies, expensive materials, drilling equipment and the involvement of specialists, this method is considered quite expensive.
The essence of technology is as follows:
- From two or four sides of the old foundation (depending on the individual characteristics of the base and the house), several inclined wells with a diameter of 15–25 cm are punched. The wells are deepened to the stop in hard rock. They should be located on the outer and inner sides of the base at a distance of 1.5 m from each other.
Punctures are made from the outer and inner sides of the foundation
- Cement or concrete of high strength is poured into the holes obtained and a reliable steel reinforcing cage is laid.
- The design is attached to the base with anchors.
After the solution dries up, a new foundation is formed from pile structures, resembling the strength and reliability of the monolith on which the structure is based.
Additional strength can be added to the structure using bored piles
In some cases, micropiles are used. Their diameter is 150-300 mm. During the drilling process, you can fill the wells with a solution. This method involves the use of drill rods. Remaining inside the pile, they provide a more reliable foundation strengthening.
Using micropiles, you can strengthen not only the foundation, but also the soil
Video: reinforcing the foundation with micro piles
To transfer the load to hard deep soils, pressed piles are used. They are installed using special equipment. The beams mounted in the base provide a good fit of the foundation and piles.
Video: reinforcing the foundation with pressed piles
The method of reinforcing the foundation with remote piles is used for elevated groundwater levels. The foundation is laid out on piles. The connecting link between the piles and the base is a reinforced concrete beam, passed through the foundation.
The foundation is laid out on piles.
Metal tubular piles
Metal tubular piles are installed on both sides of the platform. For this, a welding method using special equipment is used. To install piles, a reinforced concrete frame is mounted and connected with beams resting on jacks.
Metal piles are connected by a reinforced concrete beam
Reinforced Concrete Pad Fill
The advantages of reinforcing the platform by pouring reinforced concrete pillows are:
- reduced pressure on the soil due to the large area of the base;
- additional warming of the soil. This prevents frost heap, which is considered the most common cause of foundation damage.
The disadvantages of the technology include the inability to fill the foundation entirely, but only in sections of no more than 2 m, and the need to observe the drying time of each section before pouring the next. Therefore, this method is used to strengthen one of the corners of the base or in the event that the time and cost of filling the foundation in a circular are not critical.
Reinforced concrete cushion reduces the load on the ground and allows you to warm it
Filling the pillow under the foundation takes place in several stages:
- The repaired area is dug outside and inside the building. In this case, the blind area and the floor are removed, the earth is excavated around the base in the form of two trenches with a length of 3.0 m to 3.5 m and a depth ¾ of the depth of the foundation.
- The condition of the foundation is assessed for the presence of cracks and destroyed areas.
- If the base is in order, a hole is dug under the pillow up to 2 m long and 0.4–0.5 m deep relative to the foundation. The bottom of the pit should be flat.
- Geotextiles are laid in the pit, sand is poured with a layer of 3-5 cm and a 10-centimeter layer of crushed stone with a fraction of 30-40 mm.
- To level the surface, pure sand is poured over the rubble, and then a 5-cm layer of foam is laid.
- The reinforcing structure is laid on top and the formwork is installed.
- The base is poured with concrete and sealed with a vibrator.
- Formwork is removed after 2 days.
- It is possible to start repairing the next section no earlier than in 25–28 days.
It is important that the concrete contains as little water as possible. The optimum proportion of water to concrete is 1: 4. But too thick concrete is difficult to pour into a trench, so it can be diluted with plasticizer, sold in hardware stores.
The height of the finished reinforced concrete pillow should be at least 10 cm of the repaired section of the foundation. This will strengthen the base and reduce pressure on the ground.
In winter, repairing the foundation by pouring a concrete pad is not recommended. If there are dug trenches, protect them from frost heaving: cover the ground and cover with foam.
Video: reinforcing the foundation by pouring a concrete pad
If the shedding or destruction of the platform occurred in the basement area, this part must be replaced. It is easiest to replace under a wooden structure, as it weighs less than stone or brick.
The easiest way to replace the base is under the wooden structure.
Under the construction of stone or brick, the basement is replaced with parts no longer than 1 m with intervals between sections of at least 3 m. For work, you will need:
- crushed stone;
- concrete mixer;
- chain saw on concrete for cutting the necessary sections of the basement;
- hammer drill;
- welding machine for fastening reinforcing elements.
How to make a replacement base yourself
- To install the formwork, you need to go down to the underground, so disassemble the floor area in the house at the place where the foundation is reinforced.
- Make a chain saw 5-10 cuts, observing the distance between the extreme 1 m.
- Divide the area into small pieces with a few horizontal cuts.
- Put the cut pieces to the side and clean the surface of the base as well as the lower part of the building.
- Build the formwork in two parts: one for the outside of the house, the other for the inside. There should be holes for reinforcement on the sides of the formwork. The formwork should be 5-7 cm wider than the wall outside and inside.
- Remove the prepared formwork and install the vertical pins of the reinforcing structure into the holes with a diameter of 18–22 mm. The reinforcement sections should rise 10-15 cm above the foundation. Attach long pieces to them. After that, weld the horizontal rods so that they coincide with the holes in the formwork. It is not recommended to connect the reinforcement with a knitting wire, since this reduces the strength of the structure.
If the base is made of reinforced concrete, the house can be lifted on jacks
- Install the formwork and pour concrete using plasticizers and a minimum amount of water.
- Remove the formwork after 2 days.
- After 25 days, proceed to replace the adjacent plinth sections.
Video: replacing the base with the rise of the house
Reinforcement belt filling
If the platform is covered with cracks, but their number does not increase over time, then repairs are carried out by pouring a reinforcing belt. This allows you to prevent further destruction of the base and protect it from deformation at low temperatures, but its strength increases slightly. The reinforcing belt is allowed to be poured both around the perimeter and along one wall.
- First of all, the foundation is excavated outside the building. The outside of the foundation should be completely clear of the ground, but should not be dug deeper than a sand or crushed stone pad. The optimal width of the ditch is 0.8–1.0 m.
The outer part of the foundation must be completely freed from the ground.
- Then it is necessary to compact the soil near the foundation by manual tamping and pour a layer of crushed stone with a fraction of 30–50 mm 10–15 cm thick. Crushed stone is also compacted. A thin layer of sand is poured over it to hide sharp edges.
- A 5 cm thick foam should be laid on top of the sand and covered with tarpaulin to protect the material from sparks during the welding process.
- Further, in the foundation, it is necessary to drill holes with a diameter of 18–25 mm at a distance of 60–90 cm and drive in them segments of reinforcement that will serve as anchor fasteners. Scraps should protrude from the wall by 15-30 cm.
- To weld to them the external and internal grids made of reinforcement 10–14 mm thick, which should deviate from the base by 5–7 cm. The grids are connected together using pieces of reinforcement.
Reinforcing mesh connected by reinforcement
- In the lower part of the belt, an additional reinforcing mesh is arranged for the pillow 25–35 cm thick and equal in size to the width of the ditch. The pillow reduces the load on the ground without the need to undermine the foundation.
- After creating the reinforcing mesh, remove the tarpaulin from the foam and install the formwork. Concrete is poured in two stages. After pouring the pillow, wait 2 days, and then proceed with pouring the belt.
Concrete is poured in two stages.
- After 2 days, you can remove the formwork, and after 3-5 days, fill the ditch with earth.
Pouring a reinforced concrete shirt
A common way to strengthen the foundation is to fill a reinforced concrete shirt.
The foundation for pouring a concrete shirt is dug out taking into account the length of the tabs no more than 3 m
This method is quite simple. A person with the smallest skills in construction can fill reinforced concrete shirts alone. This will require the following materials:
- concrete grade M400;
- reinforcement for strapping the frame with a thickness of 16–18 mm.
- The foundation for pouring a concrete shirt is dug out taking into account the length of the tabs no more than 3 m. First of all, the corners are dug out and strengthened. The earth deepens 50 cm below the base.
- Arranged reinforcing cage should fit the underground part of the building from the outside. Anchors are used to increase the maximum load. The bars of the reinforcing cage should be arranged vertically and horizontally with a tie of intersecting points with a knitting wire.
All reinforcing bars must be connected with a knitting wire.
- Concrete mortar is poured into the assembled formwork. The resulting reinforced concrete cage can significantly strengthen the platform of any type.
To protect the structure from moisture, after hardening the concrete, it is necessary to create slopes
The cementation method is also called injection. This is due to the introduction of hollow tubes into the platform cracks. As a rule, it is used to give strength to the rubble foundation, which has many voids. Mortar is poured into them, and small cracks are smeared. This method is considered quite affordable, but it is used only for foundations with preserved bearing capacity.
- First, wells are drilled in the foundation.
- Install hollow tubes in them with an outlet beyond the clip of at least 40 cm and fix the solution.
- Two days after solidification, the holders of the tube cavity are filled with not very thick cement.
The cementitious composition is introduced using special injectors
Strengthening the base with tides
Sometimes the foundation is strengthened by ebbs. This technology is used to strengthen platforms made of brick or rubble stone. Reinforced concrete castings are used instead of reinforcing cage.
The procedure is as follows:
- Reinforced concrete castings are installed on both sides and wring out, while the lower part should touch the wall, and the upper one should not.
- The design is fixed with jacks and a coupler.
- Then dig trenches with a 2-meter grab.
- The ditches between the wall and the resulting structure are filled with mortar.
Reinforced concrete castings are used instead of reinforcing cage
Base reinforcement with clips
This technology provides for an increase in platform strength with double-sided reinforced concrete clips or tubes through which the solution is pumped. It fills all the voids of the masonry, due to this, the base is strengthened throughout the thickness.
- At the initial stage, you need to dig out part of the foundation to be repaired. Its length should be approximately 3 m, width - 1 m, depth - 0.5 m.
- Then, on both sides in a staggered sequence, drill through holes and insert 20 mm reinforcement bars into them.
- After this, it is necessary to attach a frame with cells with a size of 150x150 mm to the reinforcement.
- At the final stage, the formwork is installed and the resulting space is filled with concrete.
The method of reinforcing with clips allows you to strengthen the foundation throughout the thickness
The method of reinforcing shotcrete
This technique is suitable for reinforcing a not too destroyed platform or when planning an add-on superstructure. Reinforced shotcrete will reduce pressure on the platform.
With this method, a concrete gun is used, so it is better to entrust the work to specialists. The foundation is strengthened in several stages.
- A 1.5-meter ditch is being dug.
- The masonry is cleaned.
- Additional notches are applied.
The advantage of shotcrete is that there is no need to drill or drill an existing foundation
- Dug and cleaned parts are pressurized with mortar. Using a gun allows you to completely fill all the cracks.
The solution is fed under pressure using a construction gun
Video: reinforcing the foundation with shotcrete
Strengthening the strip foundation
Strengthening the strip foundation is carried out according to a special technology and includes the following steps:
- Creating a trench comfortable for work along the entire perimeter of the base, taking into account the increase in its thickness.
- Surface cleaning from contamination.
- Reinforcing frame installation.
The reinforcement cage is installed around the perimeter of the base
- The formation of a reinforced belt by welding reinforcement or tying wire.
- Creation of formwork.
- Pouring concrete.
- Waterproofing device.
Video: Strengthening the strip foundation
The most common cause of damage to the platform is soil buildup due to heavy rainfall, high water and freezing water. At the same time, the building is as if pushed out of the ground and warped. If the house is located in an area with closely lying groundwater and an unstable climate, during construction it is necessary to think over a drainage system and arrange a waterproofing of the foundation. The decision on how best to strengthen the foundation is made after examining the land and analyzing the damage.