Formwork for strip foundation: device and installation

Formwork for strip foundation: device and installation
Formwork for strip foundation: device and installation

Filling the foundation at first glance seems simple and easy. But this is just the beginning. 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 site preparation for the installation of a strip foundation formwork frame, plank structure or plywood panels for pouring concrete.

Proper formwork is the key to a quality foundation

Speaking about building a house, it must be said that the beginning of any construction is the study, calculations and marking of the construction site. Geology, geodesy and architectural plan are the main design aspects from which the new house originates.

house foundation

What is it - strip foundation formwork? This is a prefabricated structure made of boards or other materials that creates a solid container for pouring concrete. In the creation of formwork, it is important that there are fewer gaps in this structure through which concrete mortar orseeping water.

The main conditions for the design of strip foundation formwork are as follows:

  • It must withstand the pressure of concrete mortar, which sometimes reaches tens of kilograms per square meter.
  • Absence of any gaps for water to leak from the concrete.
  • The formwork installation must be designed in such a way that after the concrete has hardened, it can be easily removed.

Foundation Marking

The 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, markings are made around the entire perimeter. Level posts are installed at all corners and cords are pulled around the entire perimeter. It should be noted that during the marking process, the stakes are driven in at the corners with a margin of up to 1 m.

Foundation marking for formwork

This must be done because the trench will also dig with a margin of 20-30 cm, so that it is convenient to install formwork boards, which must exactly match the dimensions of the foundation. In fact, markup is done in two stages. The first is trench digging. The second is installed already for the formwork itself, which must strictly correspond to the dimensions of the foundation.

Installation of formwork on a stone-sand cushion

After marking the formwork for the strip foundation, a trench is dug to a depth of 1-1.5 m. Its depth depends on the quality of the soil. If it is sandy, hard ground, then the depth of the trench should correspond to the height of the foundation. In hard, rocky soilspillows under the foundation are not required. But in clay and wet areas, an additional trench depth of up to 40 cm of a stone cushion is required, on which the foundation and the whole house will stand. It needs stone and gravel. It can be both chipped and river cobblestone. To increase the density and hardness of the stone cushion, the bulk pieces are covered with fine gravel and sand, and compacted.

Strip foundation formwork

Stone-sand cushion 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.

Stone-sand cushion of stone and sand creates a solid foundation for pouring. To protect against water and moisture, the surface is waterproofed. As it is used a film or roofing cloth. Laying waterproofing material on the pillow is made in 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 structure is made of boards or plywood, which creates the desired shape for pouring concrete mortar and creating the necessary elements of the building. Regardless of the building material used for the construction of walls, in any building there are main elements and components that are common to all types of construction. This is the foundation, walls and roof. All these main elements have common

Among the existing types of formwork for strip foundations, wooden and panel formworks are most widely used. We will consider them later in the article in more detail.

  • Wooden formwork for a strip foundation, which is made from boards 30-40 mm.
  • The second type of formwork is panel formwork, created from ready-made plywood sheets. Thick waterproof plywood is used as formwork material.
  • The third type of formwork for a strip foundation is a fixed formwork made of a monolithic concrete slab.
  • And there is one more type - non-removable formwork made of polystyrene foam panels.

Formwork for strip foundations can be collapsible and disposable, wooden, reinforced concrete or metal reusable. All formwork designs have additional fasteners that secure the formwork into a rigid form for pouring concrete.

Plant structure

The most used are boards 30-40 mm thick or thick plywood sheets. Too thin boards can warp under the pressure of the concrete solution. But if there is nothing to replace them with, then to prevent curvature, you just need to hammer the racks more often. If the selected boards are too thin, then they are fixed into solid shields connected with wooden slats and nails.

Slopes for strengthening formwork boards

To strengthen the frame, wooden bars are required to the width of the formwork, to connect opposite sides. The distance between the fastening bars depends on the thickness of the boards. Additionallythe structure is reinforced with slopes, driven into the ground at one end, and attached to the board with nails at the other.

If a large heavy house is being built, reinforcing meshes or gratings are laid inside the formwork, additional strengthening of the foundation. The mesh frame is made of 5-10 mm rebar.

Installation of collapsible formwork

To install this design, you need to follow a few simple rules. First, boards or shields must be installed in a strictly vertical position. It is difficult to achieve the desired location of plank shields with pegs alone. Leveling is done with additional braces that act as spacers between the sides.

The second rule for mounting strip foundation formwork is easy collapsibility 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 solution. All boards must have a flat surface and edging. All gaps in the shields must be covered with a moisture-proof cloth.

Formwork with reinforcement

If normal boards with a section of 50 mm are used for the formwork construction, they are installed under the cord and reinforced with nails to the pegs from the outside. All pegs are sharpened and driven into the ground by 20-30 cm with sharp ends. The height of the formwork should exceed the design size by several centimeters. If there are not enough wooden blocksto work, then a thin wire is used for this. For wire ties, the pegs driven into the ground should be longer and protrude above the formwork boards.

Reinforcement - part of the strip foundation formwork

Let's just say that to create a strong concrete building, reinforcement of each part of the house is used. Reinforcement of the correct formwork for the strip foundation creates an additional strength for all parts of the building, from the foundation to the floors. Metal reinforcement is used as reinforcing materials. Reinforcing bars with a section from 5 to 20 mm. For each part of the house, reinforcing meshes are created by fastening with wire or by welding rods into a rigid, voluminous frame. Reinforcement of the foundation is carried out in the formwork troughs. Rebar with a cross section of 20 mm or more is installed in several rows inside, on each layer of concrete along the entire height of the foundation at a distance between layers of 200 mm or more. Volumetric meshes, welded from a metal rod, are laid on the bottom for the entire width, not reaching the edges by several centimeters. When erecting a concrete tie beam, vertical reinforcing meshes must be created at the installation sites of the wall frame pillars to connect with the mesh cast in the tie beam, the ends of which extend 20-50 centimeters outside.

Fixed EPS formwork

An innovative innovation in construction practice is the formwork made of polystyrene foam blocks, which remain an integral part of the walls and perform several functions. The first function of polystyrene formwork is pouringconcrete. Secondly, the formwork for the strip foundation from such blocks remains part of the walls as an insulating layer.

block foundation

Fixed formwork is manufactured at the factory. As the main raw material for the manufacture of blocks, polystyrene material is used with the addition of reinforcing fillers, which give the blocks special strength. Each piece is made with a locking device that allows installation for the building without the use of additional fasteners.

Fixed formwork laying

When laying the first row of polystyrene foam blocks for pouring concrete, a reinforcing structure is laid on the bottom of the foundation base, which creates an additional strengthening of the base. All subsequent rows are laid according to the rules of brickwork with the polystyrene elements shifted by half a block so that the joints have a checkerboard pattern.

Polystyrene formwork

Installation of formwork for a strip foundation of polystyrene foam blocks begins with the laying of rows. In each row, a reinforcing structure made of metal rods is laid, which is fastened together with wire, or reinforced meshes are created by the method of welded structures horizontally, 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, both the foundation, and the walls of the building, and its columns are a monolithic, especially strong polystyrenereinforced concrete, dressed in an insulating soundproof pillow.

Material for fixed formwork

New technologies have often been used in today's innovative groundbreaking methods. 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 vibrocompression, during which the concrete solution 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 formwork for pouring mortar. Laying concrete blocks is similar to 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.

Fixed formwork block

The second type of fixed formwork is polystyrene foam blocks. Like concrete, polystyrene formwork is assembled according to 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 of the base, because polystyrene foam blocks are 100% waterproof. The laying of fixed formwork is carried out according to the principle of brickwork with overlapping joints.

Another type of fixed formwork is fiberboard blocks, which are made using the highpressing wood shavings with the addition of magnesite. During the production process, large panels are obtained, from which fixed formwork is assembled not only for the foundation, but also for the walls.

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