How to level the foundation after pouring ☛ Tips from Builders On DomoStr0y.ru

We are asked:
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Good day, tell me what to do correctly in this situation:

Near the house there is a veranda made of white brick (strip foundation). The building is not large, 3 by 4 meters and 3 meters high.

After a snowy winter, melt water approached one side and this side began to sink. I received the following advice: make a trench on the sagging side 50-70 cm wide and approximately the same depth, take reinforcement 12 cm thick and 50 cm long and drive it 25-30 cm at the bottom into the old foundation in 2 rows at a distance of 70-90 cm and fill the trench and ends of concrete reinforcement protruding from the old foundation.

Is it right to do this? Will there be any effect from strengthening the foundation this way? Is everything correct in this advice or can something be done differently than I described. And how should concrete be poured to the ground level or to the level of the plinth, which rises almost 60 cm above ground level, I would not want to pour an extra half meter of concrete.

We answer:

I will answer from the end: no, that’s not correct, such “amplification” will have practically no effect. With the same success, you can pour a similar “beam” of concrete in a neighboring garden. If you reinforce it with a side bench (that’s what it’s called), you need to insert a whole cantilever structure made of metal beams into the body of the foundation. Reinforcement, and even with such a step, will not give any effect. The foundation will sag safely, and the only thing the constructed mass will do is an additional load on the already subsiding soil.

In each specific case, you need to look at what the existing foundation is and only after studying the situation make a decision. There are many options for strengthening foundations, and which one is suitable in your case should be decided by a specialist after an on-site inspection. In the vast majority of cases, advice from non-professionals is money wasted. And it’s good if the situation doesn’t get worse.

Only the lower part of the foundation “works”—the base of the foundation, resting on the ground. The wider it is, the higher the bearing capacity of the foundation. Therefore, to strengthen the foundations in such a case (as an option), dig a trench to the very bottom, to the base, and then dig under the base in separate sections. This is done in separate sections, usually no more than a meter in length, so as not to cause settlement of the entire structure of the house.

The excavation is carried out, if possible, at least half the width under the sole, and going downwards by at least 300 mm. It is best to carry out such work from both sides - from the street and from the room, in this case the pillow will be brought under the entire supporting part, but it is not always possible to do this (it is necessary to dismantle the floors, remove a significant amount of soil, etc.).

After the excavation is completed, reinforcing bars are placed in it, from AIII reinforcement with a diameter of 14-16 mm, in increments of 15-20 cm. The rods are located across the axis of the foundation. After installing the reinforcing mesh, the formwork is installed so that its height is at least twice the height of the slab being poured. We pour the concrete, vibrating it carefully so that the space dug out under the foundation is filled as completely as possible. We get a kind of half-clip covering the foundation from below (if similar work is done from the premises, then the tunnels are closed and the clip is completed, in the form of an inverted letter “P”).

If the foundation is made of piece materials, bentonite or rubble stone, it is necessary to make a protective jacket of concrete; in this case, in fact, holes are drilled in the foundation with a hammer drill into which anchors made of 10-12 mm reinforcement are inserted. In this case, a repair compound, or at least cement, is injected into the holes with a construction syringe. a solution prepared using non-shrink cement with the addition of PVA emulsion or another plasticizer. The anchor spacing is at least 250 mm, both horizontally and vertically.

Types of foundations

Depending on the type of soil on the site, the expected mass of the finished structure, taking into account the weight of the cladding with furniture and appliances, climatic conditions, and landscape, you can choose a base. The strongest option is a monolith - a solid reinforced slab. Such a foundation can withstand heavy loads and is actively used in the construction of multi-story and apartment buildings.

The strip base is practically not inferior in characteristics to the slab base, but it is a contour made of concrete with reinforcement, passing under each wall or partition. The tape is preferable as a support for a house with a basement, a basement, or under a fence, especially when there are noticeable differences in height on the site. The design distributes the applied pressure, while simultaneously saving time on construction and money on materials.

Under light structures made of wooden beams, frame houses, and outbuildings, piles or pillars are suitable - point supports driven deep into the ground, connected at the top by a single grillage. The grillage tape will be the primary support for the house, which will take the load first.

Features of leveling columnar foundations

A column foundation is much more economical than a strip foundation and that is why it is preferred when choosing the supporting structure of a building. It is made in the form of separate pillars made of concrete or brick, to which the load from the load-bearing structures of the building is subsequently transferred and therefore increased accuracy is required when constructing this type of foundation. Most often, a columnar foundation is made of brick or cinder block. The following recommendations will help you to display zero on the foundation and how to correct inaccuracies in the horizontal level:

Columnar foundations, made of brick, are located at a certain pitch on the site of the future construction. To lay out the top of brick foundation pillars on one level, you can resort to using a hydraulic level and sequentially transfer the zero mark to each separate foundation. When determining the deviation from a single design zero level, it is necessary to continue bricklaying to the required height.
If the deviation value is less than the height of the brick and it is not possible to deduce zero using a brick, then you can lay out high-grade cement mortar on the surface of the foundation pillars using pre-set formwork.

A video example of leveling foundations can be seen at:

It is quite possible to correct defects and level the foundation, although this will require a lot of effort and time. Correcting deficiencies in construction is always difficult and costly. It is best to carefully familiarize yourself with the technology of work before starting construction work, consistently carry out all stages of construction, and then there will be no annoying shortcomings during the construction of foundations.

How to prevent bumps from appearing

It is possible to achieve a smooth concrete surface if you pay attention to the pouring level marked inside the formwork.

To do this, inside the structure assembled for concreting, mark the uppermost points at the corners of the boards, screw in self-tapping screws or drive nails into them, stretch a fishing line or a thin but strong thread. You will get a marked contour, above which you cannot fill.

When working with an already constructed foundation, you will have to put in a little more effort.

First, the differences are verified using a building level, a leveling scheme is drawn up, the amount of material is calculated and the foundation is brought to zero.

The process of correcting the height of the structure is shown in the following video:

Since the bulk cushion cannot be corrected, as well as the lower edge of the concrete pour, you should not skimp on sand and crushed stone. The better the pillow is made, the more intact the structure will be over time.

It is possible to avoid distortion if the formwork is assembled correctly. Some craftsmen neglect side supports or assemble the mold from insufficiently thick-walled raw materials. The result is that the concrete bursts the box, bending it under the influence of its own mass. Such a distortion cannot be corrected.

Immediately after concreting, the level is checked again, the upper plane is smoothed with a spatula. To control the installation of piles or pillars, levels or rules are used - long slats, which immediately reveal curvatures.

When might alignment be required?

“Bringing the base to zero” means completely leveling it and preparing it for the subsequent construction of walls.

This procedure is often essential, as there are several reasons for performing it:

uneven foundation;
uneven masonry;
refilling of the base with a violation of evenness.

An uneven foundation is one of the most common reasons why the base has to be leveled. Unscrupulous builders may fill it crookedly, fail to maintain angles and dimensions.

If the technology for arranging the foundation is violated, the diagonals may not be observed, the width may not be sufficient along the entire perimeter, or the height of the base may be uneven. In such cases, the base will be uneven and you will have to bring it to a flat surface.

Uneven brick laying not only provokes frost heaving and shrinkage of the base, but does not make it possible to build an even base part. Often such a defect is discovered in the spring, when the formwork is removed; the foundation has different depths.

Many people try to refill the base, but this decision leads to even greater negative consequences . The way out of the situation will be to completely level the base in compliance with technology.

Consequences of an uneven design

To understand why you cannot leave the base of a house uneven, it is necessary to consider the construction of a house from the point of view of physics.

After the foundation has been erected and the basement has been laid, the construction of the residential building begins. The walls are laid from brick, aerated concrete or foam concrete, and sometimes monolithic walls made from reinforced concrete are poured.

Each stone stacked on top of each other has weight. If you add the weight of each stone together, you get a huge figure. It is this weight that puts pressure on the foundation and basement of the house.

Before residents move into the house, finishing is done , then after moving in, equipment is installed there: all these elements also have a decent weight.

If the base part is made unevenly, then the pressure distribution along the horizontal plane will be uneven. If the support under the house is crooked, excessive pressure arises in the area found, which leads to early destruction of both the foundation or base of the house.

It is better to level the base part of the foundation at the stage of pouring concrete if monolithic structures are used. When the concrete has hardened, leveling the horizontal lines will be problematic.

Correction of lateral errors

If the distortions on the sides are not severe, you can partially correct the situation. Small discrepancies are leveled out by installing a chain-link mesh and applying plaster.

For more obvious deviations from the level, a more radical method is used.

Correctly assembled formwork for the foundation

The formwork is reassembled and placed in a level position, and the voids formed between the walls of the base and the form are filled with mortar.

If the differences are more than 5 cm, a reinforcement mesh is pre-attached to the areas to be re-concreted.

Foundation strengthening technologies

There are a lot of technologies that strengthen the foundation.

Work to strengthen the foundation is carried out using special equipment.

Local renovation work

In the event that the destruction and shrinkage of the structure began recently, it is possible to do local repair work, that is, seal seams and cracks. To do this, make a small hole in the wall and then widen them.

The next step will be sealing them with cement mortar. If voids have appeared under the foundation due to running water and it has sunk as a result, then it is necessary to fill the voids with cement.

Elimination of upper defects

Horizontal evenness is important, since waterproofing will be laid on top of it and the first row of the new building will be laid. Improperly laid load-bearing walls will not be able to achieve the required level of endurance, which will compromise the integrity of the building.

To achieve zero leveling, formwork is placed on top of the poured structure, markings are applied inside, and a cement-sand screed is applied to the surface.

Tape base

To eliminate the problems that arose during the construction of the tape fill, you need to prepare cement, sand, reinforcing mesh, formwork, and bricks. The tools you will need are a shovel, a building level and a trowel.

First, the exact parameters of the differences are calculated using the level; the larger indicator is taken as the main reference point.

Aligning the tape along the top using a tie

The bricks are sawn and laid on top of the applied mortar. Brickwork is a good leveling method that allows you to simultaneously solve two problems - forming the base of the building.

A simpler option is to screed on the surface.

Monolithic slab

A monolithic foundation in the form of a slab is restored quickly; there is no need to calculate changes in several different areas.

Screeding the surface of a concrete monolith

Concrete screed is carried out over the entire surface, after setting the formwork and marking the level - errors are practically eliminated. To level the solution, a long rule is used, and liquid glass is sometimes added to the solution itself, simultaneously solving the problem of waterproofing.

Columnar support

The most economical, light weight, but not subject to use under heavy loads, columnar foundations are laid more often than it seems. Only tape is more popular, but it makes no sense to use it for wooden buildings.

Support points are pillars that are driven in with equipment or poured into the formwork using a reinforcing frame. An option is piles with a cutting screw, which can be screwed in even without special equipment.

To determine the evenness of the diagonal, several low columns formed from dry brick are placed along the perimeter of the planned building, maintaining the same distance between the points. Then, each individual masonry is leveled using a hydraulic level and leveled to a uniform height.

Identified deviations are corrected by lifting them with bricks.

Working with a columnar base to level the base

For large deviations exceeding the parameters of one brick, but much less than two blocks, high-quality concrete is laid on top of the pillar by pouring it through the formwork.

Alignment process - instructions

After acquiring all the components for repair, you can begin to level the surface of the base. This work is best done in the warm season. The process goes as follows:

Having chosen any corner of the base, you need to mark it with a marker or chalk - this will be the zero point. Next, we will need a hydraulic level, with which we will find the remaining zero points in the remaining corners of the foundation. It is better to purchase a level - a similar measuring instrument that is much easier to work with. True, it costs more.
If there is neither a level nor a building level, then you can level the foundation with bricks - more on that below. An ordinary hose is also used for these purposes. Its ends must be placed in two corners of the base, and then liquid must be poured into the hose - make sure that there are no air pockets in it. By setting one edge at the level of the zero point, you can find this indicator in other corners of the foundation.
If the water from both ends of the hose is level with the edges, then you measured exactly - fix the hose and put the appropriate marks. Of course, working with a building level will be much easier.
In each corner of the strip base where the formwork is installed, we need 2 cuts with a vertical position. Do this so that the cuts are exactly in the center of the boards. The lowest marks should be located at the level of the zero points. All we have to do is stretch a strong cord between these cuts - it will show the zero level.
Next, the process of pouring concrete to the level of the stretched cords is carried out. Done, all that remains is to level the foundation surface.

Useful tips

The formation of a sand-crushed stone layer is a stage of work at which many do not stop properly.

What needs to be done is to level the dense pillow. Differences already at this stage of laying the foundation will lead to the occurrence of differences in height even with full compliance with further technology.

The strength of the structure depends on the thickness of the laid layer: the nominal thickness of both types of raw materials is 40-60 cm. Lower values will not be able to prevent contact of concrete with underground moisture. The result is that the solution freezes, crumbles, the structure begins to gradually collapse, and one corner of the house constantly freezes.

The formwork for pouring must be made of durable materials, with supports installed, and the installation of upper fastening crossbars. Then the poured solution will not bend the panels outward, which means that the side edges will be smooth.

It is recommended to cover wooden formwork with waterproofing before concreting. Construction polyethylene is suitable. Wood has a high degree of absorbency, which is why a lot of liquid will be drawn out of the added solution. The result is that the hardened concrete will not gain the required degree of strength.

Tools for work

To level the foundation base you will need:

axe;
hammer;
bayonet shovel;
shovel;
wide trowel;
long rule;
cord or rope;
hydraulic level

You will also need accessories for mixing a solution of cement and sand if the horizontal surface is leveled using a concrete belt. This is a bucket, a drill with a mixer attachment or a concrete mixer.

In the case of a brick belt, these tools are also necessary . A cord or rope will be used to create a plumb line when leveling the side walls of the plinth: a small sinker will also be useful for this to make a level.

The hydraulic level helps to determine the zero point and start from it. Water or a colored liquid is poured into it, which is clearly visible in transparent tubes.

First, make a mark on one part of the base, extend the hydraulic level to the opposite part of the wall and also make marks, having previously tracked the fluid balance in the hose.

If the construction of a house takes place in the northern regions of the country, then the unevenness of the base can be hidden under a good layer of thermal insulation . It is recommended to do this only in cases with small differences.

What to do with the foundation after flooding?

Question:

Hello! We are in the flood zone - Khabarovsk Territory! Not today, water covered the three lower crowns (wooden house, timber 150*150mm)! The base, thank God, is high - 800 mm made of a dropout block, but it is also in the water! The foundation is a strip with a depth of 1 m to 1.1 m. Where to start when the water goes away.

Irina, Khabarovsk.

Answer:

Hello Irina from Khabarovsk!

Yes, you were unlucky this year, I sympathize. Judging by the reports, the water level at the beginning of September in some places can exceed 8 meters.

Let's hope the water goes away before it gets cold. The presence of moisture in the soil, foundation material, and wood when frozen has a destructive effect on them.

After the water has drained, you should carefully examine the condition of all structural elements of your home. After which you can make a decision about possible work. We will not consider the option of irreversible consequences.

The first step is to dry all the wet elements of the house, which, in addition to natural drying from the sun and wind, can be somewhat enhanced by artificial heating and the creation of convection, that is, blowing with air flow. Why use fires, electric heating devices, convectors? Don't take these as frivolous offers. In our area, fires are often used to warm the surface layers of the soil at the end of winter, beginning of spring (though for slightly different purposes - for possible digging of earth, early planting of radishes, etc. The foundation and crowns of a flooded house will also warm up and the moisture will evaporate faster .

A heater with a spiral and a fan, placed at home and directed at damp crowns, can dry out the wood very significantly in a few hours.

I believe that there are ventilation holes in the base and in sufficient quantities. /There are usually at least two of them for each wall, with a diameter of 10 - 15 centimeters./ A heater should be used here too. With the holes fully open.

If there are no such holes, then urgently break them in the base, otherwise the drying process may take a long time, and the underground will rot during this time.

After drying the foundation and the wood, it would be a good idea to treat both with a solution of copper sulfate.

If the foundation is damaged, then after it has dried and treated with copper sulfate, the base should be restored. Why it can be plastered (sometimes using a metal or plastic mesh, anchors and screws so that the plaster holds better). If large sections of the base peel off or fall out, repair the damaged areas with concrete, or even reinforce them in addition.

So I probably didn’t tell you anything particularly new. Nevertheless, he reminded me. Maybe someone does other operations. Since your neighbors have the same problems, communicate with them, maybe they will learn more effective ways.

Good luck!