Adding foundation to the old foundation and not making mistakes: 6 useful tips

Time has a destructive effect on any structure, and this is especially true for the foundation, which has to absorb both the load from the weight of the house and the pressure of the soil or groundwater. The decision to strengthen is made depending on the condition of the building itself: if it is satisfactory, then repairing the foundation will be more feasible than building from scratch. Let's consider in what cases the foundation of an old house can be grouted, and how to do it correctly.

Methods of restoration and replacement

After assessing the destruction of the foundation, it is restored or completely replaced. Each technology requires adherence to a certain sequence recommended by experts.

Strengthening. Minor damage to the strip foundation can be eliminated by pouring a new concrete layer around the perimeter. Restoration is carried out according to the following scheme:

• A trench is dug along the perimeter of the house, deep to the bottom of the foundation.
• The soil is removed from the brickwork with a metal brush.
• Holes are drilled in the old base and reinforcement is inserted into them.
• A mesh harness is welded to the clogged reinforcement, which will serve as the basis for the concrete pour. To ensure reliable adhesion, the mesh is screwed to the reinforcement with wire.
• Formwork is installed along the perimeter of the foundation and filled with concrete. Filling is carried out in layers, in small sections no more than 2 meters in length. After each poured layer, the concrete is allowed to soak into the soil and base.

After strengthening, the concrete will firmly bond with the old foundation and soil, the house will receive additional support area, will stop deforming, and the foundation will stop collapsing.

A comment

• Registration: Feb 2010
• Posts: 51

Answer: How to combine two strip foundations?

What is an expansion joint? what function does it perform, what does this thing look like, in general I feel in my gut that “Adding a foundation” is not worth it, but if this is the only option for an extension, how best to organize it, what I mean is that Alex and I discussed adding a boiler room to the house? how to do it better? The soil is clay and about a meter on top is artificially filled with sand.

Is it possible to do this: destroy parts of the foundation at the points of contact, connect it to the existing one with a reinforcing belt and fill in this letter “p”? and to be safe, dig holes in the corners and build something like “filled piles”?

Dismantling the old base and installing a new one

So, the house is raised, now it is necessary to remove the old frame.
So, the house is raised. Now you need to remove the old frame. To do this, use a chisel, a hammer drill and other complex powerful equipment. We are not in a hurry to throw away waste from the old foundation. They will still come in handy.

As soon as the old frame is removed, you can begin to form a pit for a new one. To do this, you can deepen the existing one a little or simply install a durable sand cushion 20 cm thick if the trench is deep enough. The sand is slightly moistened and compacted well.

• Formwork is installed in the trench, taking into account the bypass of those places where jacks and support posts are located. These holes can later be simply filled with bricks.
• A reinforcing belt is placed in the formwork, and care is taken that in the corners of the house it is bent and not welded. Since it is the corners of the building that will be responsible for the strength of the entire frame.
• The solution is poured into the prepared formwork and waited for it to dry completely.
• As soon as the concrete has dried, the crown logs are replaced if necessary. They can be tapped for rotting. If, when you knock on a log, it emits a ringing hum, then the wood is good. If the log has a dull echo, it means that it is rotting inside and requires replacement.
• Logs are replaced down to those that are well preserved.

Upon completion of all work, the house is also simultaneously and gradually lowered onto a new foundation. Windows, doors, floors and roof are returned to their place. The new foundation is sprinkled with the remains of the broken old foundation and compacted with soil.

A wooden log house is ready for use for another 30-40 years, provided that the wood is well cared for.

Foundation with rigid connection of bases

Most often, a rigid connection between the foundation of the main building and the extension is used on soils that are not subject to heaving. Most often, this method is used in the process of low-rise construction in situations where the extension is functionally connected to an existing building and is located with it under a single roof.

To make a base for an extension, a special hole is drilled in it to a depth of about 35 cm. Its diameter should be equal to the diameter of the reinforcement that will be used for driving. If the construction of an extension is carried out according to a scheme that assumes the estimated length of the reinforcement is greater than the width of the foundation, holes in the base of an existing house are drilled only part of the width. The reinforcement is installed using the anchor principle.

A rigid connection is also used in situations where the house has a recessed strip base, and the construction of the extension is planned from monolithic reinforced concrete.

A foundation with a rigid base can be available in two versions:

When installing such a foundation, the following list of works is expected to be performed:

• dig a trench, the depth of which corresponds to the existing foundation of the main building;
• fill the bottom of the trench with sand (create a sand cushion) and compact it;
• drill holes in the base;
• drive reinforcing bars with a longitudinal slot into pre-prepared holes;
• insert a wedging liner (for example, made of wood) into the reinforcement slot;
• drive the reinforcement into the holes in the corners of the base;
• form the frame using the remaining extract from the reinforcement that has already been driven in (for this purpose, parts with a length of 300 to 400 mm are specially left;
• after making the frame, fill the base tape with concrete;
• wait for the concrete to dry completely.

In order to attach a foundation to a house, you will need a whole list of equipment. First of all, we are talking about the following tools: a shovel, a building level, reinforcing bars, sand, wood inserts, a mixture of concrete and boards for making formwork.

Factors that indicate the need for foundation repair or replacement

Before starting restoration work, it is necessary to understand why the foundation was destroyed, how serious the damage is, and also determine how the damaged building can be reconstructed.

Brick foundation that requires complete replacement

Causes of damage to the foundations of wooden houses

To prevent a similar problem in the future, it is necessary to understand the factors that lead to the destruction of the foundation. And this happens for several reasons:

• geological and hydrological changes that lead to subsidence or displacement of the soil under the building;
• violation of construction technology and use of low-quality materials;
• absence or improper operation of the drainage system;
• time factor - even high-quality materials lose their performance properties over the years;
• weighting of the structure due to additional superstructures.

It is quite simple to determine whether the house is currently subsiding or whether the foundation has found new support points. To do this, beacons made of plasterboard or paper are installed in the busiest places. Their damage indicates that the destruction process is continuing.

What are the types of deformations?

The second thing that needs to be done during the research process is to determine the degree of destruction. The complexity of restoration work depends on this factor. Conventionally, 4 types of deformations can be distinguished:

1. Small defects that manifest themselves in the peeling of the foundation finishing. As a rule, the strength of the foundation does not suffer from this, and problems can be eliminated without any problems.
2. Moderate damage, indicated by cracks in the base that appear as a result of its displacement. To reveal how much the foundation subsidence is progressing, a layer of putty is applied to the problem area. A crack that appears at the slightest deformation can tell about the rate of deformation, as well as its nature and direction of displacement.
3. Significant or catastrophic damage resulting from significant subsidence, displacement, or failure of the foundation. They are revealed in the violation of the geometry of the walls, the appearance of large gaps between the crowns, and the warping of windows and doors. Problems of this kind lead to the impossibility of operation or complete destruction of the house, so urgent reinforcement or replacement is necessary.
4. Unavoidable consequences. If the moment is missed, then repairing the house will most likely be unprofitable. In this case, a decision is made to demolish the building and build new housing.

After carefully analyzing the nature and extent of destruction, a decision is made on how to reconstruct the foundation. If deformations can be eliminated and prevented in the future, then the foundation can be strengthened. Otherwise, it will need to be completely replaced.

In some cases, it is not practical to renovate a house - it is easier to build a new one

Why does deformation occur?

Deformation during foundation shrinkage

Different foundations behave differently when in contact with soils susceptible to heaving. Therefore, if the base is strip, then the new one should be the same

Another important rule: you cannot lower the new foundation below the main one.

How to determine the width of the sole of the strip base:

• You need to take a metal rod, the end of which is bent at a right angle.
• We push the rod under the structure so that the hook is positioned horizontally.
• After the rod passes the base, we unfold it so that the hook is positioned vertically, with the tip up.
• Pull the rod towards you until it stops.
• Let's make a mark.
• Unfold and pull out the rod.
• The segment from the mark to the fold is equal to the width of the sole.

Reasons for shrinkage of the extension:

• The main building has usually already settled down, but the new extension is just beginning to sink.
• Part of the attached foundation rests on imported soil, and part on “native” soil. This leads to complex deformation displacements, causing the formation of cracks in the most unpredictable places.

The consequences of natural shrinkage can be minimized by extending the construction period. To do this, we allow the foundation to stand for at least one season. The extra weight will cause some shrinkage, but not as much.

We prepare and pour the foundation for an old house

Everyone has seen at least once in their lives houses with deep cracks and warped walls.

And it doesn’t matter at all whether the old house is made of brick or wood, it’s still possible to make a new foundation

To solve this problem, you can do several things:

1. Completely replace the foundation.
2. Strengthen the existing foundation.
3. If there is no foundation at all, raise the house onto the foundation.

It is clear that these methods are radically different in terms of complexity. To understand how much, you can watch a video of pouring the foundation for a house with your own hands on the Internet.

Let's take a closer look at each of the methods of pouring the foundation for a house.

Complete replacement of the foundation under an old house

In this case, there is no other choice but to take up the arrangement of a reinforced strip foundation. To do this, the old timber house is raised using large jacks, the old destroyed foundation is dismantled and a new one is poured. Let's talk in more detail about all these works.

Raising the house

If it is not clear how to raise the house to pour the foundation, you just need to support the corners of the old wooden house. Then you need to raise those corners of the building that sag the most. For work, it will be enough to take or rent 2 jacks capable of lifting weights up to 5 tons. When one corner is raised, a wooden block or thick piece of metal is immediately placed.

It is important that when raising the sides of an old house, cracks do not appear. Therefore, you should not lift more than 20 mm

By the way, you don’t need to trust the jack 100%. To be sure, it is better to place wooden blocks under the walls every 5 mm.

Gradually it will be possible to raise the entire structure to the desired height. Install a few extra supports under the longest sides of the house, thereby protecting the builders from a possible fall.

Replacement

This stage of replacing the foundation for a house is carried out using the following technology:

• The old foundation is dismantled in its corners, we fill the base with medium grade crushed stone and only then the footing is poured.
• Then the reinforced frame is prepared. A concrete structure with it will have high strength. Do not forget to tie the reinforcement cage together, plus release the reinforcement slightly from under the base.
• Then you can make the formwork.
• While pouring concrete, use a vibrator to force out any air pockets.
• When the poured concrete dries, the remaining sections of the old foundation are dismantled and filled with new concrete, and so on until the entire foundation is replaced. In other words, it is possible to completely replace the old foundation with a new one only in separate parts. That is why it is more rational to divide the entire perimeter of the house by 2 meters. It is imperative to carry out concrete work through one segment. This will significantly increase occupational safety.

Until the foundation has hardened sufficiently, the house cannot be lowered.

Making a new foundation if there is no foundation under the old house at all

It is highly not recommended to pour the foundation for a house without reinforcement, since the foundation will not be strong and will collapse over time.

It may turn out that an old private house does not have any foundation. Then you need to “wrack” your brain on how to lift it onto the foundation without damaging it. Usually, old wooden huts were built without a foundation.

Technology for raising a house to its foundation

1. You need to dig a trench along the entire perimeter using a spade bayonet (25 cm).
2. Then logs or reinforced concrete piles should be installed under the bottom of the wooden house.
3. The dug trench is filled with crushed stone to a height of 15 cm.
4. Then the formwork is made from the inside under the house.
5. Then you can move on to arranging it using metal frame reinforcement.
6. Then you can make formwork on the outside (it is made a little higher). This will make it possible to add concrete when the formwork has already been removed.
7. Adding fine crushed stone and further pouring concrete.

Strengthen the existing foundation of an old house

If the building already has an old foundation, it can be strengthened. In other words, you need to pour a new portion of concrete under the foundation of the old house. You need to follow these steps:

A trench is being dug around the perimeter of the house. Reinforcement is driven into the old foundation. But at the same time, it is necessary not to damage the existing foundation. After the problems are eliminated, the trench is filled with concrete

It is important that the concrete mixture penetrates into all holes in the old foundation.

Foundation for a brick extension

In this case, strip reinforced concrete structures are most often used. In private housing construction, a monolithic model of such a foundation is more common; this allows you to complete a large amount of work yourself.

The work is performed in the following order:

The construction site is leveled and the future foundation is marked

In this case, special attention should be paid to marking right angles; you can check their correctness using the Pythagorean theorem. We set aside 3 m on one side of the corner, 4 m on the other, the diagonal between the resulting points should be 5 meters. After marking, you can begin excavation work, but it should be taken into account that the foundation of the extension to a brick house must be buried below the freezing level of the soil. A sand or crushed stone cushion is placed at the bottom of the dug trenches; its type and thickness must be determined depending on the type of soil

On average, it does not exceed 10-15 cm. If necessary, a rigid connection to the existing foundation or an expansion joint is arranged. The foundation structure is strengthened by a reinforcement cage. Usually it is a three-dimensional structure of 4 rods connected to each other by jumpers with a certain pitch. Formwork can only be installed for the part of the foundation that rises above the soil. In this case, it is necessary to control the verticality of its installation and the width of the foundation.

Pouring is carried out with a concrete mixture prepared in the following proportions 1:3:5 (cement, sand, crushed stone). The grade of cement must be at least 400, this will ensure the required strength of concrete. When pouring, you should carefully compact the concrete; this can be done by simply cutting off the reinforcement, but it is more effective to perform this process with a special deep-seated vibrator. In hot weather, the surface of the foundation will need to be watered several times during the hardening process, this will prevent cracking of the concrete.

Complete replacement of the house foundation

Using the house hanging method, the old foundation is removed and a new one is installed.

• It is necessary to reduce the load on the foundation as much as possible. To do this, you need to completely empty the house of all heavy things and furniture. In other words, leave only the supporting frame.
• The load of the house is calculated. To do this, you need to obtain data on the density of wood, its quantity used and the final mass. As a rule, the floors in such wooden houses are also made of wood and are lightweight. But even this must be taken into account.
• Special construction jacks are purchased or rented, which can temporarily replace the main foundation and take on the entire load.
• Trenches are dug under them. Even if water appears in the trench, it is not fatal, because the boundary level of groundwater rise will immediately be revealed.
• Then the jacks are brought in, installed under the base of the house and carefully and evenly raise it.
• The condition of the lower parts of the house is being analyzed. If the deformation does not affect them, then you can begin to dismantle or repair the base itself.
• To do this, a sand and gravel cushion is made, on which concrete or brick supports are installed at the corners of the building and at the intersection of load-bearing walls. It is also possible to install new piles, but this is only possible if there is sufficient space on the construction site.
• After installing the new foundation, the entire structure is reinforced. here it is advisable to create a flexible connection with the old foundation, if its complete dismantling is not envisaged.
• Formwork is installed into which concrete is poured. After the concrete has dried, the new base is waterproofed.
• Only after a few days is the air released from the jacks evenly and simultaneously, and the building is lowered onto a new foundation. If desired, finishing work can be carried out.

First, let's determine the type of damage and causes.

• Washing out with groundwater;
• initially incorrect construction;
• the proportions of the concrete are violated;
• insufficient amount of reinforcement;
• the depth is measured incorrectly;
• poor quality plaster;
• the piles are rusted or poorly installed;
• exposure to vibrations due to highways or construction work;
• the cladding has been destroyed over time;
• cracks will indicate that the foundation has subsided.

In general, excess water and moisture are harmful to the foundation, so it is necessary to provide high-quality drainage of the earth and sewerage.

General principles for strengthening the foundation

Strengthening the foundation along the perimeter: 1. sand cushion; 2. old foundation; 3. metal mesh; 4. anchor; 5. place of destruction; 6. formwork; 7. concrete.

Before you begin strengthening the foundation, it is necessary to conduct a thorough inspection of it. It may well turn out that initially the foundation of the building was laid with a large margin of safety, with the expectation of erecting the next floor. In this case, you are very lucky. But it also happens that the existing foundation raises many questions about the adequacy of the builders and their professionalism. Many amateur builders who are building a house for themselves or relatives without the involvement of specialists may well ignore full calculations, thinking that it will do just fine. Therefore, the stage of inspection, identification of damage and carrying out calculations is exactly where it is necessary to begin even before directly strengthening the foundation of the house.

Having completed the first stage, it is necessary to strengthen the walls. This work is carried out using both external and internal supports. It is also necessary to take into account the fact that if the house has a ground floor or basement, and you plan to deepen the building, then such work requires a scrupulous attitude. This is due to the fact that as soon as you start digging a trench along the entire length of the building before strengthening it, the load on the walls will be significantly increased and this can lead to its complete destruction. Therefore, when you start strengthening the foundation, under no circumstances immediately dig such a trench, do not expose it.

What should you do if such a continuous trench cannot be dug? This can be done gradually. To do this, you first need to excavate certain areas along the foundation of the old house. The distance between these areas should be 1 m.

Basic methods of foundation repair and strengthening.

It is necessary to dig from the corners of the old house. You need to continue digging in those places where the outer and inner walls connect. After this, an excavation is made along the entire length of the old building. At the same time, it is necessary to clean out the excavation areas as well. If it is planned to concrete a new foundation, it is necessary to provide small gaps of up to 30 cm between the new and old foundations of the building.

After the excavations have been made, it is necessary to build pits under the buildings. Reinforcement is placed in them and concrete is poured. The concrete solution must be thick and when pouring it, it is necessary to ensure that it evenly and sufficiently fills the space under the base of the building. To do this, you need to use professional equipment, in this case it is a good vibrator. After the work on strengthening the foundation is completed, it is necessary to build a blind area around the building up to 60 mm high from the ground, which should reliably protect the foundation from precipitation and floods.

In addition, it is necessary to provide for the strengthening of its walls, which is carried out in a certain sequence. Perimeter walls cannot be reinforced. First, any wall of the house is strengthened along its length, if the house has a rectangular shape. After strengthening this wall, the wall opposite is strengthened. After completing the strengthening of the walls of the house along its length, they proceed to strengthening the walls along its width.

Foundation with expansion joint

An extension to a house with a foundation with an expansion joint is most often used in industrial and multi-story construction. That is, where the soils under the structure can differ significantly in their deformation properties. For example, quite often an extension of another number of storeys is connected to an existing house of one storey by laying a foundation with an expansion joint. In any case, an expansion joint must be provided at the construction design stage.

At its core, any expansion joint, through which a foundation for another building is connected to a house, is insulation in the gap between the basement floors and the walls. Often, ordinary tow is used as this insulation. The place where the connection to the house is made is fenced off with a special decorative overlay, which is attached to the house wall.

When building a house on heaving soil, experts recommend making the floor level of the extension lower than the floor level of the main structure. The magnitude of the difference must correspond to the expected deformation.

To attach a foundation to an existing house using an expansion joint, the following significant points should be taken into account:

1. Leave a small gap between the main house and the foundation of the extension (no more than 5 cm). In order to comply with this requirement, before starting to lay the foundation, you should attach boards pre-treated with waterproofing material to the foundation of the house. In the future, it is they who will perform the function of an expansion joint assigned to them.
2. In single-story construction, the thickness of the expansion joint can be no more than 2 cm.
3. If desired, the expansion joint can be filled with any heat-insulating material. Most often, penoplex and polystyrene foam are used for this purpose. From the outside, everything is covered with a decorative overlay.

If we are talking about a small extension, it can be built on a shallow strip foundation or a foundation on stilts.

How to replace the base

If the house is already warped, a more serious reconstruction is needed; you will need to add a foundation to the old foundation along the entire perimeter of the building. More serious work will be required: the house will be raised, and then it will be put back on a new foundation structure. What to prepare for work? What tools will you need:

• shovel;
• Master OK;
• hammer;
• jacks, for lifting a weight of at least 5 tons, about 5 pcs.;
• reference apparatus.

Materials:

• gravel;
• sand;
• cement mortar;
• roofing felt;
• bars.

Progress:

• Everything possible is removed from the premises: furniture, equipment. This process is necessary to make the structure lighter; sometimes the floor, doors and windows are dismantled.
• At least 2 beams are placed under the bottom layer of timber; these are temporary supports. Ordinary beams or metal blanks are suitable; their thickness must correspond to the weight of the house, and the length is selected so that they protrude half a meter. To put them in you will have to destroy part of the foundation.
• Next, jacks are installed, and a solid foundation is placed under each of them so that it does not sink into the ground during operation. You can use an iron sheet or a piece of concrete; anything that can withstand the load will do, but in no case will the foundation support itself be suitable.
• Gradually, as the space increases as the building is raised, supports are placed under the base.
• If the walls are long, it is necessary to install additional channels so that the logs do not sag under their own weight.
• The structure is lifted evenly, trying not to create distortions; lift it a centimeter with one tool and move on to the next.
• Work continues until the house rises to the desired height. Usually 8 or 10 cm is enough.
• Then the defective base is dismantled.

After removing the old material, you need to properly add the foundation; there are some nuances here:

• dismantling and filling should begin from the corners;
• The base is replaced in parts of 2 meters through one element.

Filling is carried out according to the usual scheme:

• formwork is being built;
• a cushion of sand and crushed stone is poured;
• the solution is poured.

A small space should be left for laying waterproofing roofing felt. The house can be placed on the foundation after the concrete has completely dried.

We will conduct research of the earth to a depth of more than five meters

This will be right to create a solid foundation and will reduce finances and time in the future. Let's find out what soil and groundwater are like. These factors affect the strength of the structure:

• peat soil is unsuitable for construction; it needs to be replaced with sand or piles with screws installed;
• soil made of clay and sand - suitable for construction, makes work easier, but can swell in winter;
• sandy soil is an excellent base for a foundation; it is compacted during work; due to its flowability, the trench walls must be well strengthened;
• Rock soil is a reliable material for any foundation; it does not sag under load, but freezes at depth and requires thermal insulation for communications.

Strengthening the foundation of a house on columns

Strengthening the foundation using the drilling method.

The general case discussed above is why, how and in what sequence work is carried out to strengthen the foundation of a building. In particular cases, questions arise about how to carry out such work, i.e. pour the foundation under the old house, which is located on columns. This not only gives the building a more aesthetic appearance, but also strengthens the foundation of the house. In addition, this can make the space under the house warmer, and therefore insulate the entire house.

To strengthen the foundation in such a house, it is necessary to dig a trench between the columns from the outside of the building. The depth of the trench should not exceed the bayonet of a shovel, and its width should be equal to the width of the column. After this, sand is poured into the dug trench to a level of at least 10 cm.

On the inside, which is located under the building, it is necessary to make formwork. To do this, you can mount boards or use chipboard, plywood, edged boards with a thickness of 20-30 mm. The formwork must be secured using racks and stops. This is done so that it does not fail when pouring concrete.

Repair of the foundation of a stone house.

Then, before pouring the concrete, reinforcement must be laid. If possible, secure the reinforcement to column supports. What is suitable as fittings? This can be corrugated reinforcement, mesh, both masonry and cut, steel wire and any scraps that are lying around in the yard.

It is necessary to take into account that the outer side should not be left without formwork. Install it in such a way that the gaps left allow concrete to be poured, and after its removal it would be possible to seal the remaining niche. In cases where the formwork has significant gaps or cracks in its walls, it is necessary to use polyethylene film, securing it with a stapler. This will prevent concrete from spilling through such gaps.

The requirements for poured concrete are such that it should resemble sour cream in terms of viscosity or fluidity. As for crushed stone, use as fine as possible. If the crushed stone is large, voids may form and it will be difficult to compact the concrete.

You can avoid pouring concrete if you make brickwork instead, for which you can use old bricks from already dismantled masonry. This option eliminates the need to make formwork, and the unsightly effect of using old brick is removed by plaster from the outside. If the building has a basement and it is assumed that it will be covered, for example, with siding, then in this case there will be no need for plaster.

But even with brickwork, it is highly recommended to use both steel wire reinforcement and a sand bed. If you neglect this requirement, you can soon get a sad result in which the brick run between the supports may fail. This option is most likely for heaving soils. Don't skimp on this and don't create difficulties for yourself in the near future.

Extension on stilts

Light buildings, regardless of the nature of the base of the main building, can be erected on stilts. Various combinations and options for junction points are possible:

• Tape - piles. It is impossible to rigidly connect a “hanging” grillage to a monolithic structure, and the abutments of the facades are separated by a “warm” expansion joint.
• Piles - piles. For example, this is a common type of foundation for a foam block or frame house. Technically, grillages can be rigidly tied under the “boxes” of buildings. With wooden beams and metal profiles there are no problems with tying. And reinforced concrete beams can be tied together with reinforcement bars if their thickness allows holes to be drilled.

Finally. The connection between the extension and the main building can be done in several ways. And the choice of a particular one depends on many factors: type of foundation, nature of the soil, groundwater level, cumulative loads. It is also worth taking into account the rafter systems of both buildings, the type of roofing, and even the construction budget.

Foundation grouting technology

Adding a foundation to an old house requires the use of special tools that will raise the structure while the procedures are completed. The first step is to dig a trench around the perimeter of the house; the process has the following procedure:

1. The corners of the building are dug out.
2. Ground procedures are carried out at the intersections of walls where it will be necessary to open holes, with dimensions suitable for inspecting structures.
3. Then continuous trenches are dug around the base along the perimeter of the house.

To avoid soil shedding, the walls of the pit should have an inclination angle of 30 to 40 degrees. The width of the trench should not exceed 1 m. The depth of the pit should be below the base of the old base.

Preparatory processes for pouring concrete mortar.

The base structure is cleared of adhering soil, its walls are leveled and cleaned. If the wooden building has a columnar base, you will need to dig a hole near each pillar to assess the strength of each support. To increase safety, it is recommended to install special jacks at each corner of the building.

Preparing for work

First, we will remove the old blind area and fragments, if any. Then we dig a trench around the perimeter of the entire building, one meter wide and deeper than the old foundation. We assess her condition. Do not forget to maintain the slope of the outer wall of the trench, approximately 30–40 degrees, so that the earth does not crumble. Afterwards, the foundation base is cleaned of damage and leveled. If there are broken bricks, they are dismantled and the masonry is made again.

Video description

The video shows how to change the foundation under a wooden house with your own hands, lifting it with jacks:

Pouring the foundation

Now let's move directly to the question - how to add a foundation to an old wooden house. The first thing to do is to form the grips. These are sections of the foundation that are built in areas where jacks were installed. Their length is 1 m, and at the corners of the house 1 m on each side. Accordingly, formwork is made for them, taking into account the height of the future structure. As well as a reinforcing frame made of steel reinforcement.

The reinforcing frame is laid first, and then the formwork is built around it. It is made in the form of a box, that is, closed on four sides around the perimeter. After which the structure is poured with concrete and compacted with an internal vibrator. This process is mandatory because air always remains in the concrete mixture, which, after the material hardens, turns into pores and cavities. The latter reduce the strength and load-bearing capacity of reinforced concrete structures.

As for the concrete mortar, it is a classic mixture of one part cement, two parts sand and four parts crushed stone. All this is mixed with water until a homogeneous liquid structure is obtained. In this case, a thick mass is not needed, because pouring it into the formwork through the gap between it and the house will be difficult. Yes, and it will be difficult to compact.

The grips will remain in the formwork for 7 days, after which the wooden panels are removed. But it’s better to lower the house after 28 days. During this time, the poured concrete will reach its brand strength. You will have to lower it using jacks, which are installed next to the filled grips. Temporary supports are dismantled.

Next, holes are made in the sides of the foundation sections into which several reinforcement bars are driven. You can approach this matter differently - leave the ends of the reinforcing belt of the grips protruding from the formwork. The reinforced frame of the remaining sections of the foundation structure will be connected to them. That is, it is necessary to ensure that parts of the foundation become at least partially monolithic.

Installation of formwork

The formwork is installed under the house from the inside in a trench.

The materials are chipboard panels or boards up to 3 cm thick. They are connected so that there are no large gaps through which the solution will leak. The boards are fastened with self-tapping screws. To strengthen the formwork, metal racks are installed at the junctions of the boards. They must be placed in the corners. The posts are driven into the ground with a sledgehammer.

The upper section of the formwork is placed higher, this will make it easier to pour the mixture and seal the niche when the formwork is removed.

Possible reasons for the destruction of the building foundation

If, during a control inspection of the foundation, which good owners should carry out annually - in the spring, after the snow has melted, deep cracks are discovered on the base, then you should seriously think about urgent repairs.

Perhaps everything is not so bad - only the outer finishing layer has cracked and began to crumble. In this case, the issue is resolved quite simply. But in order to find out whether the foundation walls are affected, the cracks that have appeared will have to be widened.

Wear, deformation, and subsidence of the foundation will inevitably lead to a violation of the integrity of the walls of the entire building

So, first you need to decide in what cases cracks form in the foundation and its destruction may begin. In addition to “senile wear and tear”, that is, a clearly long period of operation of the structure, such factors include:

• Incorrect calculations and errors when drawing up the foundation design.
• Failure to comply with technological requirements when carrying out “zero cycle” work.
• When drawing up the project, no soil studies were carried out, and groundwater levels were inaccurately or incorrectly determined.
• The level of seismological activity in this region was not taken into account.
• The value of the soil freezing depth was incorrectly determined or completely ignored.

It should be noted that if the technology is violated and the calculations are incorrect, subsidence of the foundation can occur not only in an old building, but also in a newly built house.

In any case, if such a nuisance occurs, you should not give up, since almost always the foundation can be “reanimated” by using one method or another.

If you decide to carry out the process of restoration repair of the base, you must adhere to certain rules. Moreover, it does not matter which technology is chosen for this:

• The perimeter of the building is conventionally divided into sections 2–3 meters long, since the structure is strengthened gradually. First, all necessary measures are carried out on one of the sites, then on the next - and so on until the entire foundation of the building is strengthened.
• You cannot begin strengthening the foundation section on the opposite side of the building if the concrete on the strengthened side has not yet gained the necessary strength. The process of hardening of the solution must take at least seven days, and in the cold season (but at positive temperatures) - ten days.

Cement prices

cement

What is foundation strengthening and how to carry out this process

Strengthening building structures refers to activities and actions that change the mechanical properties of the strengthened element of the building. Or they change the structural structure of a unit that is in a weakened state, removing part of the load from it.

There are many methods to restore or even increase the bearing capacity of the foundation. Frequently used technologies are shown schematically in the following table (illustrations can be enlarged by clicking on them):

Restoring an element and extending its service life involves bringing its appearance to its original state by plastering or shotcrete. In some cases, it is possible to improve the mechanical properties of a structure using injections or applying a deep penetration primer.

Reasons for replacing the base

Wood beds located in the ground slowly deteriorate under the influence of dampness. In the winter cold they freeze, in the spring they thaw, become saturated with water, and swell. The processes of rotting and cracking of wood begin inside.

Operating a house for several decades in such conditions leads to complete disrepair of the logs. Therefore, the problem of how to replace the foundation for an old residential building comes to the fore.

The reasons for the destruction of the house foundation include:

• excessive load;
• calculation errors for deepening beds;
• long-term operation, during which the log foundation rotted;
• increase in the weight of the structure due to unsuccessful repair, reconstruction or expansion;
• bookmark errors;
• constant freezing of logs, which resulted in their cracking.

When defects are discovered in the building foundation, the procedure for its restoration or replacement must be carried out promptly. Delay leads to more serious problems, ranging from distortion of window and door openings, destruction of the base, ending with the building settling to the side and complete collapse.

Pouring a foundation for an old, but strong, wooden house is necessary to enable its further operation. After all, living in an unsafe building is unsafe.

Strengthening the foundation using drilling injection method

This method of strengthening the foundation of a house is one of the most modern and effective. It consists of installing piles under the base of the house or directly through the wall of the foundation strip, to the required depth, which is determined by soil surveys. A reinforcing structure is installed through the upper hole in the pipe piles. Then, through the same hole, a concrete solution is poured into the pipe, which, after hardening, strengthens the pile. As a result, the foundation receives reliable additional support points, eliminating the possibility of it subsiding into the ground.

When choosing to strengthen the foundation with piles, you need to know that several methods are used to install them in the ground. However, almost each of them will require the use of specialized equipment.

Pile installation methods

• The screw method of installing piles can be called the most commonly used when strengthening foundations, and also the most effective. In this case, the piles can be screwed in using special equipment, and sometimes even manually. However, if you choose the second option, you will have to hire assistants for this work. The piles can be placed at an angle, “piercing” through the old foundation strip. If the piles are installed parallel to the walls, that is, vertically, then they are sometimes secured to the old foundation surfaces using anchor bolts or using welding.

Piles are screwed obliquely into the ground along the perimeter of the reinforced foundation

• Indentation of piles. This method is used in cases where it is necessary to strengthen the old foundation, where vibration and impact processes are unacceptable, that is, piles cannot be driven or screwed in. Therefore, these reinforcing elements are gradually, slowly pressed into the ground. This process can only be carried out using special machines.

Prices for screw piles

screw piles

Drilled method - drilled holes are reinforced and filled with concrete, after which it hardens they turn into piles.

• Bored method. The technology for installing piles using this method involves drilling wells with a certain pitch, which is most often 1500 mm, along the entire perimeter of the building. Wells are installed under the walls of the old foundation and can be deepened into the ground up to two meters. After laying the reinforcement frame, the cavities of the wells are tightly filled with concrete mortar.

Possible options for the location of additional pile foundation supports
So, no matter what method of installing piles in the ground is chosen, they can be deepened at an angle to the structure or vertically. However, most often the option of placing piles at an angle is chosen, since it is not only more effective, but also simplifies the process of installing reinforcement in them and pouring concrete mortar. To strengthen the foundation structure, piles with a diameter of 150÷250 mm are used. And at what angle they will be installed under the base wall is, by and large, not of decisive importance.

Strengthening the foundation with “oblique” piles can be done only from the outside of the tape, or from both sides, that is, both outside and inside. Of course, if the size of the basement allows, since it will be necessary to place a special installation for deepening piles into the ground.

Advantages and disadvantages of the drilling injection method of strengthening the foundation

This technique of strengthening the foundation of a house is used not only for residential buildings, but also for the restoration of architectural monuments that have stood for several centuries. The advantages of this method include the following advantages and results that are achieved when using it:

• Not only the foundation of the house is strengthened and strengthened, but also the walls and ceilings of the building.
• The drilling injection method is applicable for restoration work for buildings of any type.
• Strengthening can be done on buildings of almost any size. The main thing is that there is enough space to accommodate the required special equipment.
• This technology of strengthening the foundation of one building does not cause any damage to buildings located close to it.
• We can use this strengthening option for houses built on any type of soil.
• When installing piles under the foundation or in its walls, the load from the structure is evenly distributed on the ground.
• If groundwater passes close enough to the soil surface, then the drilling injection method of strengthening the foundation with immersion of metal piles can be called the only one capable of saving a house from destruction. The pipe, passing through groundwater, will become a reliable protection and formwork for the concrete solution. Without it, the solution will not have the opportunity to set and gain the necessary strength, since its water will simply wash it away.

This method of strengthening has, in fact, one, but very significant drawback - the cost of the work. However, as mentioned above, in some cases such technology becomes indispensable and the only possible option for strengthening the foundation and saving the walls of the building from further deformation and destruction.

Features of the use of pile technology

Drill injection technology has passed quite serious research tests under high loads. However, you should not experiment, doing work at random, in order to avoid mistakes and miscalculations. Therefore, it is necessary to note some factors that should be taken into account when carrying out work:

• As mentioned above, the slope angle of the installed piles does not in any way affect the reliability of the created structure. Practice shows that a strong increase in the installation angle of piles increases their internal stress, and is completely unnecessary.

Gravel prices

gravel

• If you plan to mount piles directly through the wall of an old foundation, you need to make sure it is strong enough. If it is not enough, then additional strengthening of the walls will have to be done. For this purpose, a cement-injection method of strengthening load-bearing structures is often used.
• For complex soils, inert materials such as sand or a sand-gravel mixture can be used in combination with the solution that is poured inside the pile.
• When strengthening foundations using this method, the technology allows the use of metal profile pipes, round pipes of different diameters, as well as reinforcing rods of different sections. It is important to achieve maximum strength of the structure that reinforces the base.
• The length of the piles selected for installation will directly depend on how deep the dense layers of soil lie.
• The diameter of the piles depends on the strength of the foundation of the house being strengthened.
• The solution with which the pile cavities will be filled must be homogeneous, without large inclusions of crushed stone, as they can contribute to the formation of voids in the concrete monolith and reduce the strength characteristics of the support being created. Therefore, the concrete mixing process must be monitored.

Advantages and disadvantages

The advantage of the foundation grouting method is that it is possible to avoid irreversible destruction of the foundation and its complete replacement in time. Naturally, the procedure for replacing the foundation will be more expensive both in terms of financial and time resources. By pouring the foundation, the house will stand for many more decades.

The advantage of the foundation grouting method is that the procedure is not expensive and can be done independently without the use of special equipment. You can read the instructions on how to dismantle the foundation here.

Disadvantage of the foundation grouting method: this method of foundation restoration is only suitable for low-rise buildings.