Filling the foundation at first glance seems simple and easy. But this is only the first. Usually, when it comes to pouring, it turns out that this is not such a simple matter. It all comes down to several stages of preparing a construction site for installing a formwork framework for a strip foundation, a structure of boards or plywood panels for pouring concrete mortar.
Correct formwork is the key to a quality foundation
Speaking about building a house, I must say that the beginning of all construction is the study, calculations and layout of the construction site. Geology, geodesy and architectural plan - these are the main design aspects from which a new home originates.
What is it - formwork for a strip foundation? This is a prefabricated structure made of boards or other materials, which creates a continuous container for pouring concrete mortar. In creating the formwork, it is important that in this design there are fewer gaps through which concrete mortar can flow out or water can leak out.
The main conditions for the design of the formwork of the strip foundation are the following:
- It must withstand the pressure of the concrete mortar, which sometimes reaches tens of kilograms per square meter.
- The absence of any slots for water leakage from concrete.
- The installation of the formwork should be created in such a way that after the concrete has hardened it can be so easily removed.
Foundation marking
Installation of the structure begins with the marking of the construction site. For the construction of formwork for a strip foundation with your own hands, guided by the plan, marking is made around the entire perimeter. At all angles, level posts are installed and cords are drawn around the entire perimeter. It should be noted that during the marking process, the stakes are driven in at corners with a margin of up to 1 m.
This should be done because the trench will also rummage with a margin of 20-30 cm, so that it is convenient to install the formwork boards, which must exactly match the dimensions of the foundation. In fact, markup is carried out in two stages. The first is digging a trench. The second is already installed for the formwork itself, which should strictly correspond to the size of the foundation.
Installation of formwork on a stone-sand pillow
After creating the marking of the formwork for the strip foundation, a trench is digged to a depth of 1-1.5 m. Its depth depends on the quality of the soil. If it is sandy, solid soil, then the depth of the trench should correspond to the height of the foundation. In hard, stone soils, foundation pillows are not required. But on clay and wet areas, an additional trench depth of up to 40 cm of stone pillow is required, on which the foundation and the whole house will stand. She needs stone and gravel. It can be chipped, and river cobblestone. To increase the density and hardness of the stone pillow, the purchased pieces are covered with fine gravel and sand, and compacted.
A stone and sand pillow should occupy at least a third of the height of the trench. Coarse sand or gravel is poured on top of the stone layer to level the surface. On the compacted sand layer, the formwork for the strip foundation is being constructed.
A stone and sand pillow made of stone and sand creates a strong foundation for pouring. To protect against water and moisture, waterproof the surface. As it is used a film or ruberoid cloth. Laying waterproofing material on the pillow is a continuous, waterproof layer. The joints of the waterproofing panels are glued with adhesive mastic or tape and poured with concrete mortar 30-40 mm into the formwork for the strip foundation.
Types of formwork
The construction consists of boards made of boards or plywood, which creates the necessary shape for pouring concrete mortar and creating the necessary building elements. Regardless of the building material used for the construction of walls, in any building there are main elements and nodes that are common to all types of construction. This is the foundation, walls and roof. All these main elements have the general principles of construction.
Among the existing types of formwork under the strip foundation, the most widely used are wooden and panel ones. We consider them further in the article in more detail.
- Plank formwork under the strip foundation, which is made from boards of 30-40 mm.
- The second type of formwork is a panel, created from ready-made plywood sheets. Thick waterproof plywood is used as the material for formwork .
- The third type of formwork under the strip foundation is a fixed formwork made of a monolithic concrete slab.
- And there is one more view - fixed formwork made of polystyrene foam boards.
The formwork device for the strip foundation can be collapsible and disposable, wooden, reinforced concrete or metal reusable. In all formwork designs, there are additional fasteners with which the formwork is fastened in a rigid form for pouring concrete.
Board construction
The most used - boards with a thickness of 30-40 mm or thick plywood sheets. Boards that are too thin may bend under the pressure of the concrete. But if there is nothing to replace them, then to prevent distortion you just need to hammer the racks more often. If the selected boards are too thin, then they are fastened in solid panels connected by wooden battens and nails.
To strengthen the frame, wooden blocks are required to the width of the formwork, for connecting opposite sides. The distance between the fastening bars depends on the thickness of the boards. Additionally, the structure is reinforced by slopes, one end driven into the ground, and the other attached with nails to the board.
If a large, heavy house is being built, then reinforcement meshes or gratings are laid inside the formwork, additional reinforcement of the foundation. The mesh frame is made of 5-10 mm reinforcement.
Installation of collapsible formwork
To install this design, you need to follow a few simple rules. Firstly, boards or boards should be installed in a strictly vertical position. Pegs alone make it difficult to achieve the right arrangement of board shields. Alignment is done with additional bars that act as spacers between the sides.
The second rule of installation of the formwork of the strip foundation is easy folding of the structure. To do this, you need to strengthen all the posts and bars to the boards from the outside, so that when disassembling the nails can be easily pulled out. It is also desirable to seal the bottom of the trench with a waterproofing layer to prevent water leakage from the concrete mortar. All boards should have a flat surface and edging. All slots in the shields must be covered with a moisture-proof cloth.
If normal boards with a cross section of 50 mm are used for the construction of the formwork, they are installed under the cord and fastened with nails to the pegs on the outside. All pegs are sharp and with sharp ends hammered into the ground by 20-30 cm. The height of the formwork should exceed several centimeters of the design size. If there are not enough wooden blocks for work, then a thin wire is used for this. For wire ties, pegs hammered into the ground should be longer and protrude above the formwork boards.
Reinforcement - part of the formwork of the strip foundation
Let's just say that to create a strong concrete building, reinforcement of each part of the house is used. Reinforcing the correct formwork for the strip foundation creates an additional strength for all parts of the building, starting from the foundation and ending with floor ceilings. As reinforcing materials, metal reinforcement is used. Reinforcing bars with a cross section of 5 to 20 mm. Reinforcing meshes are created for each part of the house by wire bonding or by welding rods into a rigid, voluminous frame. Foundation reinforcement is made in the formwork gutters. Reinforcement with a cross section of 20 mm or more is installed in several rows inside, on each concrete layer along the entire height of the foundation at a distance between the layers of 200 mm and more. Volumetric nets welded from a metal rod are laid to the bottom over the entire width, not reaching the edges by a few centimeters. When constructing a concrete strapping beam, it is necessary to create vertical reinforcing mesh in the places of installation of the pillars of the wall frame to connect to the mesh, flooded in the strapping beam, the ends of which go out 20-50 centimeters.
Fixed formwork made of expanded polystyrene
An innovative innovation in construction practice is the formwork of polystyrene foam blocks, which remain an integral part of the walls and perform several functions. The first function of polystyrene formwork is concrete pouring. Secondly, the formwork for the strip foundation of such blocks remains part of the walls as an insulation layer.
Fixed formwork is manufactured in the factory. Polystyrene material with the addition of reinforcing fillers, which give the blocks special strength, is used as the main raw material for the manufacture of blocks. Each part is made with a locking device, which allows installation for the building without the use of additional fasteners.
Fixed formwork masonry
When laying the first row of polystyrene foam blocks for pouring concrete, a reinforcing structure is laid at the bottom of the foundation foundation, which creates additional reinforcement of the foundation. All subsequent rows are laid according to the rules of masonry with the displacement of polystyrene elements by half a block so that the joints have a chessboard formation.
The installation of formwork for a strip foundation of polystyrene foam blocks begins with the laying of rows. An reinforcing structure made of metal rods is laid in each row, which is fastened together by a wire, or reinforced meshes are created by the method of horizontal welded structures if the formwork is prepared for load-bearing walls. If the work is performed only under the vertical columns of the building, then welded metal structures are made. Thus, the foundation, and the walls of the building, and its columns are a monolithic, especially strong polystyrene reinforced reinforced concrete, dressed in an insulating soundproof pillow.
Material for fixed formwork
In modern innovative methods of laying the foundation, new technologies often began to be used. This is a fixed structure that is left on the walls of the foundation. There are several types of such progressive formwork. These are concrete blocks and polystyrene foam forms. The first are made by vibropressing, during which the concrete mortar is compacted to the density of natural stone. Such blocks have great strength and do not require additional reinforcement of the foundation. There is no answer to the question of how to make formwork for a strip foundation , since the concrete blocks themselves are the formwork for pouring the mortar. Laying concrete blocks is like assembling a constructor. Each block has special locks for connection. The connection density of the blocks is very high and does not require any additional protection against the flow of the solution.
The second type of fixed formwork is polystyrene blocks. Like concrete, polystyrene formwork is assembled behind the principle of the designer. The advantage of such formwork is that it is simultaneously used both as a support for the foundation, and as an insulating layer, and as a waterproofing base, because polystyrene blocks are 100% waterproof. The laying of fixed formwork is carried out behind the principle of brickwork with overlapping seams.
Another type of fixed formwork is fibrolite blocks, which are made by high pressing of wood chips with the addition of magnesite. In the production process, large panels are obtained, from which the fixed formwork is assembled, not only for the foundation, but also for the walls.