How to make a foundation for a foundation

An important stage in the construction of the foundation is the formwork. Formwork is the form in which concrete is poured, it is installed immediately after the preparation of the site and the trench for the foundation. The article will tell you how to properly make the formwork for the foundation.

Formwork can be removable and non-removable. Fixed formwork is performed in the case where no removal of material from the foundation surface is required. Examples include fiberglass or polystyrene boards, which are often used to build a slab foundation - they also serve as a heater.

In private construction, a strip foundation is usually used, for its erection use a removable formwork made of finished metal panels, plywood or boards. Requirements for it are very high:

• The formwork must be strong enough to withstand the pressure of the concrete on the walls;
• The formwork dimensions must be strictly maintained;
• There should not be any cracks through which the solution may leak;
• The fastening of the elements is done so that the formwork can be disassembled when the foundation is solidified.

Purchased metal shields have a high strength and smooth surface, they are easily attached with a bolted connection and quickly removed from the finished foundation, leaving a smooth and even surface. However, they have one drawback - the price. For developers who build dozens of houses per season, the costs of acquiring shields are justified, but when building a foundation with their own hands, it is more expedient to collect boarded or plywood formwork.

Construction of wooden formwork

Formwork made of boards or plywood, made by hand, is a shield on a frame of bars, which are fastened together in a single structure. Shields are strengthened by means of screeds, cuts and clamps. Shields are installed in a prepared trench so that all the fasteners are outside, and from the inside turned out to be an even and maximally flat surface of the required shape.

For edging formwork, an edging board is suitable, it can be of the second grade, or birch plywood. The thickness of the material is from 10 mm. The frame of shields is collected from a bar 40x60 mm. Slopes, clamps and screeds can be made from any improvised materials, usually for this purpose use the remains of boards or a bar. The main thing is to ensure sufficient strength and qualitatively fix them.

The inner surface of the formwork from the unplaned board will not be smooth enough, but if you are planning to warm the foundation or its exterior finish, this circumstance will benefit rather - the plaster solution and the glue fall much better on the slightly rough surface.

Formwork technology from boards or plywood

Prepare the material for the shields. The bars are cut into the same lengths, half a meter longer than the height of the basement. One side of the bars is sharpened - with their help the shields are slaughtered in the ground. The boards or plywood are also cut to the size of the boards. The boards are carefully adjusted so as not to leave any slots. The thickness of the material is chosen depending on the size of the foundation and, accordingly, the thickness of the concrete, which will press on the formwork. In most cases, enough boards with a thickness of 24-36 mm.

Lay out on a flat surface bruski at a distance of one meter, align them along the top edge, put boards or plywood on top and fix with nails or screws. The cap of fasteners should be located exactly on the inside of the shield, otherwise the protruding point of the nail or self-cutter will seriously complicate the removal of the formwork.

Fastening formwork

When making a foundation with an expansion in the lower part, the boards rest on the support board, without the need to stick them into the ground, and cut the bar along the width of the shield.

Mark the site, pulling a nylon string between the blocks pounded into the ground. By marking, dig a trench of the required depth, perform a sandy-gravel podsypku.

Install the support board if necessary, and after it - shields, fixing them to the board or driving a pointed piece into the ground. In this case, use a plumb and level, achieving the most even position of the shields.

The boards are fastened together with the help of cutting boards, nailing them from the outside to the boards of the boards. The sides of the formwork are clamped together by U-shaped constructions of a bar or boards that do not allow the sides of the formwork to disperse when pouring concrete. The angles are additionally fastened with boards, fixing them to self-tapping screws.

Fastening of formwork boards with each other

If the boards are not sufficiently stable, they are also fixed with spacers from the bar sections from the inside and from the outside. The slopes are a bar cut at an angle of 45 degrees and installed between the ground and the shield.

For additional stability, the formwork is secured with spacers

. The bottom and the board walls of the boards are lined with a dense polyethylene film to avoid seepage of the solution and premature evaporation of the cement milks.

Install the reinforcement from the rod and pour concrete. Level the surface, cover with a film and stand until the concrete sets.

The bottom and walls of the formwork are covered with a plastic film

You can remove the formwork when a small gap appears between the boards and the concrete foundation. When removing the shields, it is necessary to tap them lightly from the outside with a rubber hammer, this will allow to remove the formwork with the least effort. First remove the screeds, stakes, clamps. After this, the shields are alternately removed.

If a film has been used, it can not be removed from the surface of the foundation until it dries completely - this will prevent premature drying of the top layer and allow the concrete to gain maximum strength.

Shields for plywood and board formwork can be used many times, and to facilitate their removal, it is better to lining the formwork each time with a film. The formwork can also be combined - this type of formwork is often used in loose soils when making a pile-tape or buried foundation. In this case, the underground part is made non-removable from asbestos-cement pipes or polystyrene sheets, and above-ground part - removable, from boards or plywood.

Video - how to make formwork for foundation