How to properly pour the foundation under an old wooden house

Sooner or later, any foundation under the house has to be changed or repaired. The house begins to change its position, cracks may appear, and windows and doors jam. All these signs indicate the need for repair or complete replacement. In this article, we will try to tell you how to properly pour the foundation for an old house without violating the integrity of the structure. After all, only competently and correctly done work will give you a guarantee that your house will stand firmly for more than a decade. However, in order to take on this business with confidence, you should carefully understand all the subtleties of this process.

It is not always rational to use special construction equipment to repair or replace the foundation, and it can also be problematic to fit it to the house without harming other buildings and planting horticultural crops. Therefore, it is important to know what tool you may need in the course of the upcoming work and prepare it in advance:

Jacks. At least 4 pieces. They can be of any design, but it is preferable to use hydraulic ones. It is important when choosing them to take into account that they can lift a load of at least 10 tons in weight, therefore, they must be able to develop sufficient force. If you do not have them available, then it would be wiser to rent them than to spend money on their purchase;
Sledgehammer, steel scrap or jackhammer;
Wedges of various sizes;
Temporary supports, which can be used as bricks, massive beams, durable boards of various thicknesses, metal beams or chocks;
Shields made of beams or boards with a size of at least 250 square meters. see, which will serve as the basis for jacks;
Steel plates about 5mm thick. so that the force from the jack rod is evenly transmitted to the lower rims of the structure;
Concrete mixer. It will be required in order to prepare a cement mortar. With a large volume, this will be difficult to do manually;
Reinforcement, the thickness of which will be at least 12mm;
Mortar materials: cement, crushed stone and sand. Their number depends on the size of the foundation;
waterproofing materials.

The procedure for performing work and the features of each stage

Foundation replacement or repair does not accept haste and haste, everything should be thought out to the smallest detail. Before starting work, it is necessary to find out the bearing capacity of the soil and the depth at which groundwater lies.

Neglecting these parameters will lead to the fact that the new foundation for the old house will quickly become unusable, as it will be affected by the strong pressure of frozen soil. Based on the data obtained, a calculation is made of the depth of the foundation and the features of its installation.

Raising the house from the foundation

In order to avoid problems at this stage, you need to start work by making props at the corners of the house. Start lifting the house from the most sagging corner. Using two jacks, evenly raise the angle on both sides.

It is recommended to raise the corner no more than two centimeters, otherwise multiple cracks may occur. Every 5mm. lifting, bars are placed to insure the failure of the jack.

Raising the corner of the house from the foundation. 1 - lower crown of the log house, 2 - lever from the board, 3 - support for the lever, 4 - old foundation

On the outside of the house there will be a jack from the inside, a support lined with bricks. To do this, you have to raise the floorboard;
The jack and support should be installed as close as possible to the foundation, so you reduce the load on the lever. Do not forget to lay out a brick platform under the base of the jack;
A metal channel or beam can serve as a lever for raising the corner of the house;
With slow movements of the jack handle, we begin the rise. The main thing here is to prevent the outer end of the lever from slipping off the jack platform, so every 2-3 strokes, check whether everything remains in place;
After lifting the corner into the resulting gap, it is necessary to place supports. They need to be placed on stable planes.

Further, the remaining corners rise similarly, but the height of their rise should be less. Long walls require additional supports so that they do not sag. From now on, the house will be suspended in the air. For obvious reasons, work on dismantling the old foundation should be started immediately, otherwise, due to subsidence of the soil, the house may sink again.

When repairing a foundation, parts of it that need to be replaced are removed. If it became necessary to completely replace the foundation, it is necessary to remove individual segments not exceeding 2 meters in length. They are dismantled through one using a heavy sledgehammer and steel scrap or a jackhammer. This technology will ensure complete safety of work.

Digging a new trench

The trench is dug from the outside of the house. Its depth depends on the condition of the soil and the size of the house. If the foundation needs to be brought under the inner walls, then excavation will be complicated by the fact that the amount of excavated earth will increase, because you will need free access to these walls.

A pillow of sand and fine gravel is laid at the bottom of the trench for strength. For its greatest strength, sand is moistened with water and rammed with an ordinary wooden block.

Foundation formwork construction

Formwork is installed on the inside of the trench directly under the house. To do this, use boards or chipboard boards. The boards are interconnected in such a way that there are no large gaps at the joints, otherwise the solution will come out. For their fastening, wood screws and a screwdriver are used, and a hacksaw may also be required.

Boards with a thickness of not more than 3 centimeters are installed along the edge of the trench and fastened together;
At the points of their connection, metal racks are installed for greater strength of the entire structure. In the corners of the trench, their installation is mandatory;
Racks with a heavy hammer or sledgehammer are driven into the ground. As an additional reinforcement, you can use wooden struts, which are installed at an acute angle relative to the formwork, or pull the formwork with a jumper installed between two opposite posts.

Options for reinforcing formwork for strip foundations

It is important to remember that the top edge of the formwork should be as high as possible. This will make it easier to pour the mortar and make it easier to close the niche after the formwork has been removed.

In order to be sure of the strength of the foundation, you need to reinforce its base. For this purpose, steel wire, grating or metal rods are suitable. They are laid on a sand and gravel cushion and interconnected by tying or welding.

Backfilling in trenches rubble. In various sources, you can read that crushed stone of various fractions is used to backfill the trench, but this is far from the case. It is not recommended to use large fractions, since this can lead to uneven filling of voids with concrete. Therefore, it will be more competent to use crushed stone of small fractions, which will provide maximum strength to the foundation.

Foundation reinforcement scheme

Foundation pouring and formwork removal

For pouring the foundation is being prepared, consisting of one part of cement and three parts of sand. In a concrete mixer, it is brought to the desired consistency. The resulting mixture is poured into the formwork. It is important not to forget about the compaction of the mixture.

Then you need to wait for the concrete to dry completely. It is important to remember that these works must be carried out at a temperature not lower than +5 degrees and that the design strength of the corner support pillars must be observed.

Do-it-yourself concrete

Formwork removal.

After the concrete is completely dry, you can proceed to the removal of the formwork. If this is not done and the formwork is left, its wooden elements will rot, which, in turn, will lead to premature destruction of the foundation.
Drying time depends on the ambient temperature. On average, this takes one to two weeks.
It is necessary to start dismantling the formwork with protruding and corner elements. It is in these places that the concrete dries the fastest.
While these elements are removed, the rest of the foundation will have additional time to dry and harden.

You need to remove the formwork very carefully, otherwise you can damage the finished foundation for the old house.

After the corners are dismantled, you can proceed to the removal of the formwork on the main spans. It is important to remember that during the removal of the formwork, the vacated places are covered with earth and carefully compacted.

If you neglect this stage, or perform it without the proper level of responsibility, you can expose the foundation under the old house to excessive moisture during rains or melting snow, which will inevitably lead to its premature destruction. It is important to choose the right waterproofing materials and correctly apply them to the walls of the foundation. It must be remembered that the waterproofing layer must be applied without possible damage and breaks.

Vertical waterproofing is located from the base of the foundation to the level of rain moisture. It also protects the horizontal waterproofing outlets. When choosing a material, the properties of the soil must be taken into account. Ideally, these are foam boards or asbestos-cement sheets.

The task of horizontal waterproofing is to protect the walls of the house from capillary moisture. It is located between the foundation and the walls of the building. Materials for horizontal waterproofing are presented on the construction market in a wide range, so their choice is yours.

lowering the house

After the waterproofing work is completed, the house can be carefully lowered to its original place. To do this, the support beams are removed very carefully, one after the other, evenly. The main thing is to ensure that the house sits tightly in place without gaps.

As you can see, subject to the necessary requirements and a responsible approach to work, it is possible to repair or pour a new foundation under an old house on your own.

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