Replacing the foundation under a wooden house. Replacing the foundation under a wooden house - methods, technical nuances Replace the foundation under the house
Over time, the building may shrink. This occurs due to violations of construction technology, natural aging, geological and climatic conditions. Raising a house and replacing the foundation is a fairly common option for major renovations. There are other ways to restore the integrity of the building's foundation. Before starting work, the main thing is to correctly determine the degree and cause of shrinkage of the building. Sometimes it is necessary to change the entire structure of the foundation under the house.
Foundation replacement and repair methods
The most popular method of replacing a foundation is raising the house on jacks. You may need from 2-4 to 10-12 pieces. Raise the building by installing jacks on both sides of one wall. Lifting diagonally is unacceptable.
In one go they reach a height of 1.5-2 cm, no more. Temporary supports are immediately inserted into the resulting space. Additional jacks are installed in places where the lower edges of the frame deflect.
Another method involves removing a layer of soil under the house, 200-250 mm thick. After this, the wooden crowns are replaced and the foundation of the house is repaired.
Methods that are labor-intensive and require special skills include complete dismantling of the walls for a convenient approach to the foundation. After this, the base structure is repaired or completely replaced. Then the walls are reassembled, replacing rotten and deformed elements.
If the wear is minor, cosmetic repairs may be sufficient. This is the cheapest restoration method.
What type of base to choose
It happens that the old foundation has failed and needs to be completely replaced. Before replacing the foundation under an old wooden house, you need to decide which type of foundation is best suited for the given geological conditions and type of construction.
Types of foundations and their characteristics are presented in the table:
| № | Base type | Properties |
|---|---|---|
| 1 | Tape | It is a monolithic or prefabricated concrete strip that can withstand significant loads. For small wooden buildings, a shallow foundation is sufficient. But if the site is dominated by heterogeneous soil or water-logged soil prone to frost heaving, then you need to choose a different type of foundation. |
| 2 | On screw piles | Screw piles are driven into the ground. They can be combined with a grillage or operated without it. This is an inexpensive type of base that can be quickly installed with your own hands. Suitable for light buildings built in areas with differences in relief, deep levels of ground freezing, and small flooded areas. |
| 3 | On bored piles | Allows you to reduce land work. It consists of wells filled with cement mortar, interconnected by concrete beams or a slab. |
| 4 | On brick, stone, concrete pillars | The pillars are mounted in increments of 1-2 m; installation is required at the points of intersection of walls and in other places with a maximum load-bearing load. Is a reliable support for small light buildings. |
The type of foundation for a wooden house is chosen depending on many factors. If it is difficult to make a decision and calculate all the loads yourself, it is better to turn to professionals who will help you make the right choice.
Foundation replacement
Replacing and repairing a foundation will require some knowledge and patience. In order not to completely destroy the building, you need to do the work slowly, strictly adhering to the technology.
Jacks can be rented from the railway depot; they must be designed to lift loads weighing 10 tons.
Bricks, strong beams and boards can be used as backing elements.
Before raising the house, lighten its weight as much as possible. They dismantle the floors, take out furniture and all household items.
Under the jacks, a base is made in the form of a square of wood with sides measuring 50 x 50 cm.
Calculations
In order for the new foundation to serve as a reliable foundation for the building for a long time, its parameters must be correctly calculated.
When calculating, you need to take into account:
- soil freezing level;
- proximity to underground sources;
- seismic activity;
- relief of the site;
- soil type;
- a lot of housing construction.
The foundation is buried at least 500 mm under load-bearing walls, and at least 400 mm under partitions.
Raising a house with jacks
They make a platform for jacks. Install it slightly deeper into the ground, at a distance of 50 cm from the corners of the building. The jacks are secured to a wooden stand.
Simultaneously, both sides are lifted to a height of no more than 2 cm in one go. Jacks are placed in places where the wood has not lost its strength. Lifting devices cannot be installed in rotten areas.
To properly transfer the load to the logs, it is necessary to provide for the installation of metal plates that perform the function of a gasket.
Immediately place strong backing elements into the resulting gap. Raise all the walls one by one until the desired height is reached. They check the stability of the building; it should not be mowed. Firmly fix the desired level by installing support elements.
Dismantling the old foundation
After raising and securing the wooden house, the foundation is repaired or dismantled. These works are quite easy to do with your own hands; you will need several assistants and simple tools: a crowbar and a sledgehammer.
If you carefully dismantle the old foundation, the remaining intact materials can be used for further construction work.
What you need to know
The degree of shrinkage of a house depends on the type of soil and the level of location of underground sources. If they are close to the surface, you need to provide a drainage system around the perimeter of the house.
If the soil is prone to landslides, it is strengthened. To do this, fill the area around the foundation with a mixture of liquid glass and water or drill small wells and pour resin into them.
If groundwater is close, winter soil heaving will be significantly higher. Freezing groundwater increases in volume and pushes everything in it out of the soil. When melting, the volume of water decreases and shrinkage occurs.
Installation of foundation on screw piles
If you decide to build a new foundation on screw piles, you need to calculate their length and diameter. You should not skimp on material, since the reliability and safety of your home will depend on its quality.
To construct the foundation of a small wooden house you will need 8-12 screw supports.
Step-by-step instruction:
- After raising and securing the house building, I-beams are laid under its load-bearing walls and partitions. They are cut 5-7 cm longer than the estimated length. In the future, they will serve as a grillage.
- In pairs, at a distance of 300-400 mm from the walls, screw piles are screwed in, which are the support for the beams. Make sure that the structures are positioned clearly in level.
- To add strength and protect against corrosion, the pile cavity is filled with concrete mortar.
- A head is placed on the upper edge of the support, and the grillage channel is attached to it.
- Dismantle the old base.
- They carefully lower the house.
The columnar foundation is mounted using the same technology as the installation of a screw foundation. The only difference is that you need to dig wells for the pillars, which are subsequently filled with concrete or laid out with bricks.
Installation of strip foundation
They prepare the site, remove construction debris, plant root systems, and sweep away dust.
Instructions on how to change the foundation of an old wooden house with your own hands:
- They dig a pit below the freezing level of the soil and below the location of the old foundation. The shape of the trench should be U-shaped so that it is convenient to remove the reinforcing frame and make its bundle.
- Pour sand onto the bottom in a layer of 150 mm. Moisten and compact. Pour a layer of crushed stone and compact it well.
- Metal rods with a cross-section of 12-16 mm are tied into two longitudinal rows connected by vertical jumpers.
- Formwork is made from boards; it will serve as a form for pouring cement mortar.
- Concrete solution is poured. At the same time, openings are provided for installing jacks to lower the building.
- After it has completely hardened, the formwork is dismantled.
- Temporary supports are attached to the poured foundation. Work is beginning to replace the foundation on the other side.
- Openings for jacks are filled with bricks.
- Check the integrity of the lower crowns and floor boards. If there is any damage, the damaged elements need to be repaired. Rotten and damaged areas are cut out and replaced with new ones.
- Work is being carried out to waterproof the foundation and basement of the building.
- Smoothly and carefully lower the house onto the new foundation.
There is another technology, according to which support columns are first poured at the corners of the house, and then, after drying, the house is supported on them and a concrete strip is installed around the entire perimeter. All other stages correspond to the sequence described above.
You can watch the video to see how to restore and raise a house:
Replacing the foundation is a job of increased complexity. You need to realistically assess your strengths and skills in performing construction work. If a mistake is made, workers may be injured or the building may be destroyed. If you lack strength and knowledge, it is better to hire professionals with experience in this field.
A common problem with old wooden houses is high wear of the foundation. Such changes are visible to the naked eye: the house is askew, walls or doorways are sagging. If such problems are multiple in nature, it is necessary to urgently repair the foundation. The house is in danger of being destroyed if the work is delayed for another couple of years. For this reason, restoring the foundation is in many cases a pressing and important task. Before laying the foundation for an old wooden house, it is necessary to conduct an inspection and assess its condition. A thorough analysis will allow you to decide on further work.
Foundation inspection
When assessing the foundation, it is worth adhering to a certain technology. The foundation inspection is carried out as follows:
- a trench 50-70 cm wide is dug around the foundation;
- the foundation material is determined;
- inspected for damage.
Attention! In case of minor damage, you can do without replacing the foundation: it is enough to strengthen the existing foundation of the old house.
Types of foundation
After inspecting the old base, you need to decide what type the new one will be. The choice of design depends on many factors, such as the type of soil and the weight of the house. As a rule, the following types of foundations are used in the construction of wooden houses:
- stone (usually brick)– brick is an inexpensive material, but it is destroyed by moisture;
- reinforced concrete - the most durable of all types of foundations, it can be strip and monolithic;
- pile - a foundation constructed of metal piles is very practical and quickly erected;
- wooden - oak columns (blocks) are placed along the perimeter of the foundation; such a base is very susceptible to fungi and moisture.
The modern variety of materials makes it possible not to use outdated types of foundations in construction. The most practical and durable options are reinforced concrete and pile foundations. Some foundations can be properly strengthened.
Lifting the house
When the question arises: “how to make a foundation for an old house?”, you immediately need to decide how to raise the house. These works are carried out regardless of the type of future foundation of the building.
Preparatory work
To raise an old house, it is not necessary to use expensive special equipment. The most democratic option is jacks. To determine the load capacity and number of jacks, you need to calculate the approximate weight of the house. All furniture and household items are removed from the building - this will lighten its weight.
The work will require a large number of wooden or brick support pillars; they are prepared in advance. The height of the supports should correspond to the height of the future foundation. The number of supports depends on the length of the walls. To regulate the minimum difference in the height of the supports, you will need pads; the best option is boards.
During the lifting process, the lower crowns of the house are the most vulnerable place. To protect the logs from scattering and cracking, they are fastened with metal staples. If the house structure has an old foundation, it is necessary to destroy its outer foundation, approximately 50 cm along each side. This is done for further installation of jacks. To figure out how to add a foundation to an old house, it’s worth knowing all the intricacies of raising a building.
Installation of jacks
Jacks exert very strong pressure on the logs, so they are installed on unbroken logs. Installation of jacks is carried out as follows:
- under the place where the jack will stand, place a strong support in the form of sheet iron, thick plywood or a timber base (size 50x50 cm);
- The most sagging corner of the house is determined and a jack is installed under it, on the prepared support;
- install jacks at subsequent corners.
Note! Raising an old house with your own hands is problematic - for safety reasons the work is carried out by 2-3 or more workers.
Lifting process
The lifting of the house begins from the most sagging corner. All actions are performed very smoothly so as not to damage the walls of the house. In the first approach, a lift of 2 cm is performed, this will prevent cracking of the walls. Wooden blocks or planks are placed in the resulting gap.
When the first corner is raised, the subsequent ones are raised one by one to the same height. Supports in the form of planks are laid along the entire perimeter. The lifting is carried out gradually, placing supports in the gap to lighten the load on the jacks.
After the house is raised to the desired height, brick or wooden supports-pillars are installed. Just like for jacks, support platforms from solid material should be prepared for support pillars. Only after this can you begin repairing the old foundation.
The entire process of raising the house is completed within 24 hours. The last stage is preparing the site for the future foundation. If the house is dilapidated, it is raised with extreme care.
Destruction of the old foundation
After raising the dilapidated house, they begin to destroy the old foundation. The traditional and less expensive way is to work with a sledgehammer and wedges. Wooden stakes are driven into seams or cracks in the foundation using a sledgehammer. To destroy the remaining cement elements, a hammer drill and a crowbar are suitable.
A shovel is used to remove the resulting debris. After the foundation of the old house is destroyed, they begin to prepare a place for a new foundation.
Important! As the destruction of the base of the building progresses, brick or wooden supports are installed along the entire perimeter.
Pouring strip foundation
The most reasonable option for one-story wooden buildings is a strip reinforced concrete foundation. It is suitable for any type of soil. The construction of such a foundation is carried out as follows:
- Digging a trench. The basis for the new foundation should be 10-20 cm wider than the previous one. If in the future it is planned to build other buildings on the site, the foundation should be poured for them as well;
- A U-shaped trench is created under the longest walls;
- The first layer of sand (10-15 cm) is placed in the trench;
- The next stage is the installation of a frame made of reinforcement;
- Formwork assembly;
- Laying waterproofing inside the formwork;
- Pouring the solution.
After the solution has completely hardened, boards are laid on one section of the foundation, on which temporary supports are laid. All sections of the base are poured one after another. The reinforcing mesh of each new section of the foundation is connected to the outlets of the rods of the previous sections.
With another method of constructing a foundation, the corners of the structure are poured first. Limited sectors are created in the formwork at the corners of the proposed foundation. They are poured first. After the solution has hardened, fill in all remaining areas of the base.
After pouring, the openings for the jacks are paved with brick or mortar. When the base has completely hardened, the lower logs are re-inspected and replaced if necessary. The final stage of work is installing the house on the foundation: the work is carried out smoothly, gradually lowering the structure by 3-5 cm.
Replacing an old foundation with screw piles
With the fast speed of work, installing a pile foundation takes a day. This type of house foundation is quite suitable for sandy and marshy soils.
Before purchasing piles, you need to calculate the weight and area of the house and study the type of soil underneath it. The average load-bearing capacity of screw piles is from 5 to 14 tons, depending on the span of the blades and the diameter of the pile itself.
Work on installing the pile foundation is carried out as follows:
- raise the house using jacks;
- mark places for future piles (most of them are located in the places of load-bearing walls and corners of the house);
- install piles manually or using equipment (burying structures above the soil freezing level);
- after screwing in all the piles, they are combined with a metal frame by welding;
- The final stage is installation of the house on a pile foundation.
To reduce heat loss and improve the appearance of the building, the structure is covered with brick or decorative panels.
Results
To build a new foundation under your home, they first conduct a series of studies. They are aimed at determining the condition of the foundation. It is also necessary to know the intricacies of lifting a structure using jacks. They begin to lift from the more sagging edge. Care should be taken when working with the lower crowns. Experienced builders use brick as a material for temporary supports.
It is easier to replace a strip foundation than other types of foundations. It is necessary to competently approach the installation of formwork and pouring concrete. When installing a house on a foundation, it is also worth considering several features of the process.
Replacing the foundation under a wooden house is required when all existing methods of strengthening it do not guarantee the proper result (). When performing this operation, sometimes it is even necessary to change the type of foundations of the structure itself.
Practical experience in this area has been enormous - a huge number of wooden houses have been built in Russia (and are still being built).
Over time, the rickety houses had to be repaired, so the technology for resuscitating wooden buildings has been worked out to the smallest detail.
The main operations that need to be performed during the replacement process under a wooden house are:
- preparatory work;
- raising a house;
- dismantling the old foundation;
- construction of a new one;
- installation of a log house on a new foundation.
All work is carried out without the use of heavy equipment - it is enough to have several jacks with a lifting capacity of up to 10 tons.
Preparatory work
At this stage, available materials are prepared - beams, boards, steel plates with a thickness of five millimeters. This entire set is necessary for the construction of temporary supports for the log house and support platforms for jacks.
If the house was built with a fence, it will be completely dismantled.
The house is made as light as possible: the furniture is taken out, the floors are dismantled. Houses with stove heating present some difficulty. Sometimes you even have to dismantle the stove - for example, if it is built on a common foundation with the house. There are cases where the roof was also dismantled.
To provide a strong support for the jack, boards made of boards measuring 500x500 mm are knocked together.
Lifting the house
Raising a wooden frame is the most crucial moment in the foundation replacement technology (). They lift it using jacks installed at a distance of half a meter from the corners of the building.
It is advisable to simultaneously raise the house from both sides (but not diagonally!). The amount of lifting in one approach is no more than 1.5-2 cm. Temporary supports are immediately installed in the resulting gap.
If, during lifting, pronounced deflections of the lower crowns of the frame occur, additional jacks are installed in these places.
Dismantling the old foundation
Once the house has been raised to a sufficient height and placed on temporary supports, the foundation can be dismantled.
They perform this operation using any tools - a chisel, a crowbar, for example - as long as it is convenient for them to work.
The choice of suitable tools depends on the type of foundation. Brickwork can be broken with a crowbar; for monolithic reinforced concrete, you will have to select more serious equipment.
The foundation is completely dismantled down to the cushion.
Construction of a new foundation
A trench is dug in place of the dismantled structure. Its depth must exceed the depth of the previous foundation.
You should first clarify the depth of soil freezing in a given area. Perhaps this factor was not taken into account when building the house, which led to deformation of the load-bearing structures.
Further actions consist of constructing a new cushion, knitting the reinforcement cage, then lowering it into the trench and pouring concrete (
Most foundations, after a certain period of time, begin to crumble or slant to the side. This happens especially often with support bases made of pillars. If construction technology was not followed during the construction of such a foundation, after a while many supports fall on their sides or begin to bulge.
Such processes affect the condition of the entire structure. The house may tilt, cracks appear in the walls, doors stop opening, glass in the windows cracks. In this regard, it is worth understanding when the foundation under a wooden house is being replaced, what is required for this and what features of the process should be taken into account.
When required
There are many cases when replacing the foundation of a house becomes necessary:
- The old structure is seriously deteriorated. This can be indicated by rotten wood, crumbling rubble masonry, or brick that has turned to dust.
- If at least one of the support pillars is destroyed, the structure of the building may be damaged.
- As a result of erroneous calculations, the piles were noticeably askew.
- There are tears or cracks in the base strip. The solidity of the foundation of the old house has been broken.
- The log house began to sink to the ground.
If each of these reasons appears, you should think about replacing the foundation. Before making a final decision, you should invite a specialist. He will be able to calculate everything correctly and advise how to strengthen the foundation. It is also worth deciding what is more appropriate: repairing the old foundation or building the house anew.
The most common cause of problems is the old columnar foundation, which, after improper installation, begins to fall on its side. Any defect in its production technology can cause destruction. This leads to deformation of the base and the collapse of the house on one side. A sign of such changes are difficult to open windows and doors. In this case, one of the only correct decisions is to pour a new foundation.
Replacement methods
To understand how to replace the foundation under a wooden house, you should understand the purpose of the repair measures. The amount of materials and the amount of effort expended will depend on this.
You can replace the foundation of an old wooden house using several methods:
- Cosmetic. This method is the most accessible due to small financial investments. If part of the base is rotten or collapsed, it is worth putting a wooden element in its place. Cosmetic repairs to the foundation of a wooden house cannot replace a full foundation. Subsequently, the integrity of the structure may be compromised.
- With dismantling the walls. In this case, the walls are completely dismantled. At the same time, the lower link is replaced.
- Dismantling the base. When choosing this method, the crowns of the lower part of the frame are replaced. The method allows you to thoroughly restore the foundation of a wooden house.
Strengthening the foundation located under the log house involves the use of jacks, bars, support beams and other materials. To figure out how to raise a wooden house and pour the foundation, it’s worth familiarizing yourself with the popular technology. It is used for log houses and timber houses.
The house is easy to lift without the use of special equipment. Hydraulic jacks are used for this purpose. They are capable of lifting loads up to 10 tons. If you use jacks, you won’t have to plan to purchase equipment. Such units can be rented at railway depots.
Replacing the foundation of a wooden house is carried out using:
- crowbar - it is convenient for them to manually dismantle the old base;
- sledgehammers - will also be needed to destroy the remaining remains of the foundation;
- wedges
To create temporary supports, thick beams, fresh lumps, and high-quality bricks are selected. Boards can also be used. They act as gaskets. Jacks should be installed on a reliable base, the sides of which should not be less than half a meter. For such sites, beams and boards are knocked down.
Advice! To figure out how to strengthen the foundation, you need to take into account the type of soil.
In order for the jacks to act on the crowns with equal force, it is necessary to find a steel plate. Its thickness should not be less than 5 mm. Replacing an old foundation with a fence involves dismantling the latter. Before work, furniture is taken out and the floor base is dismantled.
The process of replacing the foundation of a wooden house with your own hands takes several weeks (taking into account the hardening time of the concrete).
Procedure
The foundation restoration process is divided into several stages. Each of them must comply with certain requirements. Replacing the base by strengthening your base is quite simple:
- Installation of jacks. If you lift one jack faster than the others, the lower logs will bend and may break. They are installed where the rot has not yet reached.
- Raising the house. The walls can be raised 6 m from their previous position. After this, the rotted elements are removed, and scraps of beams are attached as supports. Tow soaked in an antiseptic is first placed between the log and each beam. It is worth adding a 10 cm layer of gravel to the site of the future foundation. You can raise the house at a time no more than 2 cm on each side. After each lift, temporary supports are installed to record the achieved result.
- Removing the destroyed foundation. When the structure is already at a sufficient height and secured with temporary supports, you can begin to dismantle the old foundation. The brickwork is dismantled with a chisel and crowbar. Some of the remaining materials that have retained their functional characteristics are used as the basis for a new foundation.
- New foundation. For one-story buildings, the MZF foundation is more often chosen. Before construction, a trench is dug. Its depth should be greater than that at which the old foundation was located. At the excavation stage, it is better to think about digging a trench not only under the house, but also under future extensions. First, a U-shaped trench for the foundation is dug on one side of the house. After it is installed, the same work is carried out on the opposite side.
A sand cushion is poured into the bottom of the trench. Then a frame is knitted from reinforcement. Next, the formwork is installed. It must have waterproofing. Now you can pour the concrete mixture. After the solution has hardened (after about two weeks), you need to lay boards on the first section of the foundation, and place temporary supports on them. The frame of each new section of the tape is connected to the outlets of the reinforcement of the previous section. A video on replacing the foundation of a wooden house with your own hands is at the end of the article.
At the last stage, the house is lowered onto a new foundation. If necessary, change the lower crowns. The beams that secure the house to the jacks are cut off. They are installed under the outer walls of the building.
Column and pile foundation
If the log house stands on brick pillars that still retain their functions, but are already noticeably cracked with time, it is worth putting them in a concrete belt to strengthen them. The concrete layer is 20-30 cm. You need to dig trenches around the pillars, make a sand cushion at the bottom, and then install the formwork. After the first layer of concrete is poured, a continuous metal mesh is laid.
If repairing some pillars is pointless, you will need to raise the building. In this case, the destroyed supports are laid out from scratch.
Skewed piles are straightened without the use of special equipment. In order for them to take a vertical position, they make an undermining from the side opposite to the distortion. Then the piles should be straightened and the space around them should be filled with concrete mixture. If the support is deformed, it will have to be replaced. As an alternative, asbestos-cement pipes 200 mm in diameter filled with liquid cement can be used. Before installing the pipe, a gravel-sand cushion is laid at the bottom of the pit.
The pipe should also be strengthened from the outside - for this, gravel-cement mortar is used. The well should expand downwards. At the bottom it should be made in the shape of a mushroom cap. In this case, the pile will acquire additional stability.
