Vladimir wrote to me in a personal message, I see there is a question here, so I’ll copy my answer here:
"Hello. The most likely reason for the formation of cracks, as you already guessed, was frost heaving. With such a high level of groundwater, your loams are very heaving. The freezing depth of your soil is 1-1.2 m, but since all the structures are reinforced concrete, then the soil freezes much more strongly along them. As a result, you have 2 dangerous influences: from below, under the grillage, the force of frost heaving acts directly, and on the side, on the surface of the same grillages and piles, the tangential forces of frost heaving act. They are weaker than direct forces. , but still significant. Especially for light houses that are not capable of loading. Unfortunately, there are no photographs that would help exclude other possible causes. This could happen if they were tied to the existing wall. foundation with reinforcement - then the cracks would have passed, but these 0.5 meters, but you don’t write about such a connection. It is also possible that the foundation of the extension bent, the reinforced foundation did not crack, but the unreinforced blocks cracked. What you should do:
1) It would be a good idea to take photographs, post them on any photography site and send me links - this will allow me to evaluate everything more accurately (we need general photographs that show the pattern of crack propagation).
2) As you have already decided - replace the soil under the grillage with polystyrene foam with a thickness of at least 100-150mm.
3) Backfill with non-heaving soil, for example a sand-crushed stone mixture. But here you need to be careful - such a mixture allows water to pass through well - it is necessary to plan the area around it so that surface water does not flow there or accumulate.
4) Insulate the blind area around the building and the adjacent part of the house with polystyrene foam (50mm thick), as well as the concrete wall above the foundation to a height of 1m (yours is 800mm, which means its entire height).
5) After backfilling and before insulation, it is necessary to seal all cracks with fine-grained cement-sand mortar. Including concrete foundation blocks, there is no need to change them yet. In 1 year after all the work (except for the insulation of the concrete wall), it is necessary to observe what was achieved. If everything is fine, then insulate everything else. While the concrete wall is not insulated, cover the extension around with snow for the winter (take snow 5 meters away, no closer).
There is no need to widen the grillage - you will only increase the deformation! "
answerHello, I really hope for your help. I don’t even know what to do, my hands have completely given up. And so on in order. Development region Penza. A TISE foundation (six-wall with two internal load-bearing structures) was erected for the planned two-story or one-story house with a half-attic, made of GRAS D500 B3.5 aerated block with a thickness of 375 mm. house size 11 by 9.5 m Number of piles 44 grillage width 45 height 50 cm. piles 250 mm. extension 600mm depth 1.7 meters. grillage hanging from the ground 15 cm. I made a foundation, waterproofed it and left it for the winter. I arrived in the spring and everything seems to be fine. In the summer, I laid hollow-core floor slabs and lined them with bricks around the perimeter in three rows, waterproofed them and again left them to winter. This spring I came back and saw everything was fine again. I decided to make blocks. In May, I delivered and unloaded 30 cubic meters onto the foundation and began to slowly lay them down. I reinforce with steel reinforcement 8 under the windows and every 4th row. All that remains is to lay out the last row and fill in the reinforcement belt. And then by chance I saw several microcracks surrounding the grillage. The cracks are really as thick as a hair. and they are where the air is. I am posting the longest photo, where it is the bottom of the grillage without coating with mastic. By the way, the grillage was reinforced with steel reinforcement 12, four from the bottom, four from the top, plus vertical and transverse from 12 every 50 cm. And they poured M350 factory-made concrete, although it was diluted a little with water during the process, it was very hot and the concrete froze instantly. Why do you think cracks might appear? After all, there are no hints of cracks in the brickwork, but I laid it last year. What should I do? I’m building one. So much work. Well, I poured out my soul. What do you advise me in this situation? 
What to do if the foundation is cracked? The foundation is cracked - what to do, this happens and you shouldn’t be upset about it! Better roll up your sleeves and get to work correcting mistakes made during the construction or design of the foundation. Well, in addition to the most sincere sympathy for your grief, we can offer fairly detailed instructions, following which you can get rid of cracks in the foundation, which will prevent further destruction of the house. Cracks in the foundation of a house, in most cases, appear due to miscalculations by architects who overloaded the grillage. In addition, some cracks are the result of violations of the construction technologies used in the construction of the foundation. For example, a classic mistake - neglecting the reinforcement of masonry - leads to uneven distribution of load on the soil and subsidence of the soil. As a result, both the foundation itself and the load-bearing walls of the building burst. But, if you lay a 4-mil wire between the first and second layers of brick, repeating this operation in the upper layers of the masonry (in increments of three rows), then there will be no cracks either in the wall or in the base. Similar advice can be given regarding the reinforcement of window and door openings. The row of bricks that cover the opening should be reinforced with the same 4 mm wire. Otherwise, the crack will go not only up, but also down, subsequently cracking the base as well. Another reason for the appearance of cracks is the close proximity of building materials with different densities, for example, brick and reinforced concrete or brick and wood. Such neighbors have completely different physical properties, therefore, when one material freezes or becomes saturated with moisture, the second may crack, right along the border of contact between brick and concrete or brick and wood. Therefore, to avoid cracking the foundation of the house, try to avoid such proximity or reinforce horizontal seams in adjacent layers of masonry. In addition, all stepped foundations constructed with a difference in grillage heights are at risk. Both the foundations and the brick plinth, which is built in between the base filler strip and the beam grillage - when the upper or lower beam subsides, the plinth masonry will simply burst. The foundation has cracked - what to do? If your precautions did not work and your foundation nevertheless cracked, then you will have to fix this defect. Moreover, repair work must be carried out immediately, literally the next day after the first cracks are discovered on the base or in the wall masonry. Repairing a cracked foundation is done by strengthening the foundation wall or strengthening the supporting soil layer. In rare cases, a major repair of the base may be required, with a complete replacement of the supporting elements and partial replacement of the grillage elements. What should you do immediately? Urgent foundation resuscitation begins with an inspection of the foundation body. In this case, it is necessary, based on visual data, to make a decision on the use of one technology or another. The foundation of a brick house was cracked during repair work. After all, if cracks have formed in the upper part and have not yet reached the bottom, then one method of treating the foundation is needed. Well, if the cracks started from the bottom, then a completely different technology is needed. It would also be a good idea to have a professional evaluate the soil characteristics. But this work is not done immediately. Therefore, if your priority is speed, then you will have to abandon geological surveys. How to strengthen a cracked foundation Strengthening a foundation can be achieved by strengthening the base, introducing reinforcing mesh into the body of the foundation, or placing additional piles (supports) under the base. An alternative technique is to increase the thickness of the base or install reinforcing screeds and insulating panels over the cracks. You will simply build up the foundation, thereby increasing its load-bearing capacity. In addition, to combat cracks, you can use technology to strengthen the supporting soil - the soil under the foundation. By implementing special operations, it is possible to reduce the groundwater level and reduce the depth of soil freezing. As a result, the bearing capacity of the soil will increase, and the foundation will stop sinking deeper into the soil. Elimination of cracks in a strip base To treat a strip base, the following set of restoration technologies is used: firstly, strengthening the base with bored piles, secondly, strengthening the soil with a drainage system, thirdly, strengthening the soil by arranging a heat-insulating blind area. Piles installed under the base in the form of a crossing X-shaped support will keep the foundation strip from subsiding into the ground. Drainage will increase the depth of groundwater, reducing the amplitude of soil heaving deformation. Thermal insulating blind area will reduce the depth of soil freezing, or even completely eliminate this process, preventing the very possibility of subsidence of the foundation. The simplest technologies for screeding strip masonry are based on installing two crutches connected by a clamp into the base body. Moreover, such a structure works both as a screed and as a shock absorber, taking on the force that breaks the body of the foundation. Well, the crack itself can be filled with concrete or reinforced with epoxy resin. After installing the screed, X-shaped support or blind area, you need to install a marker mark that records the current state of the crack. To do this, two “cakes” of epoxy mass are attached along the edges of the crack, and a thin wire is pulled between them. If this thread does not break during the winter-summer season change, then it is considered that the crack was fixed successfully and all destructive processes stopped. What to do if the foundation slab is cracked? Slab foundations have good load-bearing capacity and cracks in such foundations are very rare. But if such a nuisance does occur, then you will face the most tedious procedure - complete or partial replacement of the base. Unfortunately, it is impossible to stop the destruction of the slab. Therefore, get ready to dig tunnels under the slab, strengthen the walls at the split site, remove the damaged part and fill a new section mounted on block or pile supports. But even such manipulations cannot guarantee further destruction of the foundation. Therefore, a house on a cracked slab will most likely have to be rebuilt.
The word “grillage” itself is of German origin and is formed from two words: Rost - lattice and Werk - structure, structure. A grillage is a horizontal building structure that connects the pile supports of a building into a single hard disk, which is the foundation of a building or structure. The information contained in this article will help you learn how to make a grillage from reinforced concrete.
The reinforced concrete grillage is made after driving the piles. Pile foundation supports can be made of metal pipes, reinforced concrete pillars and bored piles.
Classification of grillages
Grillages according to their horizontal position are divided into three types:
- An elevated or above-ground grillage is located above ground level. Such foundations are made in wetlands or where there is a threat of seasonal flooding or there is a high groundwater level. The building seems to hang on stilts above the ground;
- The ground foundation is made in such a way that its top coincides with the zero level of the construction site. Such grillages are made when the foundation base does not have sufficient load-bearing capacity to support a building of another type;
- Low or underground grillage is used in the construction of large industrial facilities. To construct it, a pit of small depth is dug, at the bottom of which a layer of frost-resistant soil is poured. The top level of the foundation is below the general zero level.
Rationale for using a grillage
Attaching the grillage to the pile
The grillage can be thought of as a ski on snow. Where a person stands confidently on skis, without them he will fall into the snow. So, foundations of this type are used in areas with moving and unstable soils.
A grillage is much more expensive than a strip foundation. Therefore, before proceeding with the construction of the foundation, it is necessary to inspect the foundation of the construction site and determine the feasibility of using piles and grillage. Each building or structure project includes a feasibility study of a foundation of one type or another. As a rule, a modern grillage is made in the form of a reinforced concrete platform.
Design
It is better to entrust the calculation and design of the foundation to specialists. When designing a facility, engineers take into account the results of geological survey work reflected in a vertical survey of the area, the depth of soil freezing, the height of the future building, snow load and many other factors that determine the actual load on the foundation of the building. Based on the collected data, structures are calculated.
Preparation
Before starting work, the types of building materials, their brands and quantities are determined. Create a work schedule. Before pouring concrete into the grillage, you need to know what grade of cement and reinforcement will be needed. The concrete mixture can be prepared at the construction site using a concrete mixer or directly in a trough - it all depends on the volume of concrete.
Formwork work
Installed grillage formwork After driving the piles, they proceed to installing the grillage formwork. Along the perimeter of the base of the future building, formwork is installed with a height equal to the thickness of the foundation slab. The fencing is made of boards or construction plywood. Plywood is a very durable, reusable building material. Therefore, you can take it from a construction site where the foundation has already been made.
The sides of the formwork are reinforced on the outside with stops made from available material. The supports should not allow the formwork boards to creep away from the pressure of the concrete mixture. Any gaps in the formwork are unacceptable. Cement laitance will leak out through them and the result will be concrete of poor quality. On a previously prepared soil base, with the top layer previously removed, a cushion of crushed stone or gravel-sand mixture is arranged.
Waterproofing
The entire surface of the base is covered with a layer of waterproofing material. It is economically beneficial to use a special polyethylene film as waterproofing. In places where they exit to the outside, the ends of the piles are tightly wrapped in waterproofing material and secured with wire. The edges of the insulation are placed on the sides of the formwork and brought above the height of the fence. After this, the integrity of the waterproofing surface is carefully checked and all cracks are eliminated.
Reinforcement
In places where load-bearing structures will rest, rods are laid more often and of larger diameter. The tops of the piles must be connected to the reinforced frame. This is done by welding. Embedded parts are welded onto the reinforcement in close proximity to the metal parts of the piles. Then they are connected to each other using electric or gas welding. Thus, they ensure a monolithic connection of piles with a grillage and uniform distribution of the load from the building to the ground.
Pouring the grillage with concrete
The final stage of work is pouring the grillage with concrete. Concrete is made in various grades. From grade M 100 to grade M 500. The higher the number, the higher the strength characteristics of concrete. In foundations such as grillages, high-strength concrete is used. If the mixture is prepared directly at the construction site, then you need to know how much cement, crushed stone, sand and water to put into the concrete mixer per batch and in what proportion. The grade of cement, fractions and type of fillers determine the grade of concrete. In case of a large volume of work, you can order a truck mixer with ready-made concrete mixture to be delivered to the construction site. The grillage needs to be filled with concrete at one time. If the pouring process is interrupted, concrete with impaired strength characteristics may be obtained. After watching the video, you will learn how to correctly fill the grillage formwork with concrete.
As concrete is poured, it is compacted by squeezing air out of its mass. When compacting concrete, use any available tool suitable for mixing the solution. Special vibrators operating from the electrical network are effective in this work.
Using a geodetic tool, the horizontal surface of the grillage is controlled. The installation of special beacons also ensures horizontal distribution of poured concrete over the surface of the foundation.
Curing
Formwork dismantling process Concrete hardens and gains full strength within a few weeks. All this time, you need to protect the grillage from excessive exposure to the external environment. To protect the concrete surface from precipitation, make a cover from a polymer film. In hot weather, cover the surface of the grillage with a wet rag. After the foundation is ready, the formwork is dismantled.
The developer can independently calculate and build a grillage on piles. You can select a ready-made construction project similar to the future building, use the Internet, and get advice from specialists. You can learn how to make a grillage by asking neighbors whose houses have stood on such foundations for more than one year. All this is advisable to do during the construction of small projects, when the costs of designing a structure can make up a significant part of the total construction budget.
Loading...