Foundation Formwork: How to Avoid Mistakes and Perform Installation

Foundation Formwork: How to Avoid Mistakes and Perform Installation

Any construction requires the organization of a reliable foundation. In order to give the concrete foundation the necessary shape, a special design is used – formwork. It can be of different types depending on the features of the structure. Formwork foundation is carried out in several stages. It can be made from different materials. Self-assembly of the structure requires studying the instructions and observing the installation rules.

Formwork: what is it? Construction assembly conditions

In order for the foundation to take shape after pouring, various materials are used from which the formwork is assembled. Most often, such structures are made of wood. There are more modern options that are constructed from polymeric materials that are distinguished by high technical characteristics. Foundation formwork performs the following functions:

  • creates the form necessary for the concrete base to harden;
  • gives an even surface texture;
  • isolates the structure from the soil (if necessary).

In order to answer the question about what formwork is, it is necessary to become more familiar with the features of this design. Proper installation of foundation formwork requires certain conditions to be met.

First of all, it is necessary to prepare the soil in the place where the foundation of the future construction will be filled. It must be completely cleaned of debris and impurities.

The foundation formwork consists of individual elements. Shields made of wood or other suitable material are used as the forming base. On the inside, which will come into contact with the concrete mortar, there should be no contamination. The surface should be as flat as possible. This will minimize the finishing work after dismantling the molds.

When installing the formwork, special attention should be paid to fixing the individual components together. The quality of the fixing elements determines how well the foundation formwork will cope with the forming function. Illiterate fixtures can cause concrete deformation.

The formwork for the column foundation (as well as strip or monolithic) must be completely tight. Only in this case the correct molding of the base is possible. Before proceeding with the installation of foundation formwork, it is necessary to familiarize yourself with its possible types.

Removable formwork
Removable formwork is very quickly dismantled after concrete hardens.

Varieties of designs: fixed and removable formwork for foundations

Currently, there are two types of formwork. Distinguish between removable and fixed structures. Each option has its advantages and disadvantages, which should not be ignored. Let us consider these varieties in more detail.

Removable. This type of structure is dismantled after solidification of the base of the building. In the future, all the structural elements used to assemble the form can be reused. To organize such formwork, wooden materials are most often used.

This option is standard and is used when pouring foundations of varying complexity. Removable formwork is also suitable for individual building elements. For walls and ceilings, this technology is used no less often.

Fixed Forming formwork of this type, unlike the previous version, is not disassembled. Such designs are technologically advanced and have some advantages over standard forms.

Note! Non-demountable formwork performs a heat-insulating function, protecting concrete from exposure to low temperatures.

Fixed structures are made of polymer materials of various degrees of manufacturability. The most widely used polystyrene forms. This is due to the fact that this material has an acceptable cost. Such foundation formwork is used in the construction of monolithic structures as the most appropriate option.

Fixed formwork
Fixed formwork made of polystyrene foam – multifunctional and reliable

Separately, it is worth mentioning the fixed forms made of wood. In order to more clearly assess the differences in various designs, it is recommended to study their photos. Formwork of this type is most often used in the case when you need to perform a narrow bath foundation, located at a shallow depth. After pouring concrete, this design is simply covered with soil.

Combined formwork: design features

In some situations, combined structures are used to form the base of a building. The mixed version, which includes elements of removable and non-removable formwork, is recommended to be used if the building is being built on loose soil.

Such a formwork of a house includes two layers: external and internal. From the outside, standard forms are used, which are assembled from boards. In turn, the inner side is represented by polystyrene foam. To fix the polymer material to the soil, nails with a length of 200 mm are used. Joining of expanded polystyrene with wooden material is carried out using self-tapping screws.

The main advantage of the combined design can be called the fact that it performs both auxiliary and heat-insulating functions. The foundation is protected from the sides and from the side of the sole.

Scheme of bilateral (A) and unilateral (B) foundation strengthening
Scheme of bilateral (A) and one-sided (B) foundation strengthening: 1 – rubble foundation, 2 – anchor, 3 – reinforcing mesh, 4 – formwork, 5 – concrete mix

When installing such a formwork around the house with your own hands, you must remember that thermal insulation can be arranged either in the underground part, or throughout the entire depth of the base. In the event that the polystyrene foam elements are located to the full depth, then you need to take care of the organization of fasteners. To do this, dowels are inserted into them in advance, allowing you to fix the block on a concrete surface.

Useful information! The upper tier of the foundation formwork is constructed using standard wooden boards reinforced with spacers and stakes.

What you need to know when choosing a material for formwork

Forming structures used to fill the foundation can be assembled from different materials. The following criteria affect the choice of foundation formwork type: the type of foundation, its width, length, etc. To assemble the form, the following materials are most often used:

  • wood;
  • polystyrene foam;
  • metal;
  • reinforced concrete.

Wood. As mentioned above, the forms for the foundation of this material are most often found. Formwork panels in this case may differ in their design. The most common use is sheet plywood, which is fixed on spacers made of wooden boards.

The advantage of a wooden structure is its accessibility. It is also worth noting that the cost of this form is quite low. Wooden elements are mounted relatively easily. All that is needed is to know the technology of work and adhere to it. To install this design does not use sophisticated specialized tools.

Expanded polystyrene formwork
Expanded polystyrene formwork has become very popular due to its practicality and functionality.

The main disadvantage of formwork for concrete made of wood is the need to use additional elements. This is necessary in order to strengthen the design. Most often, this need is due to the overall differences of the individual parts of the form. The organization of this formwork requires a mandatory preliminary calculation of materials.

Styrofoam. The second most popular material. The constituent elements of a fixed structure are made from it. In addition to performing the formative function, it is a good insulation, protecting the foundation of the building from low temperature, wind and water. This design is easy to install, but its cost is not too affordable. Problems can arise when selecting individual constituent elements.

Reinforced concrete. People wondering what to make of formwork often choose other, less popular materials. Reinforced concrete can be given as an example. In private construction, this method is practically not used, since the final cost of the work is too high. And also it is worth noting the complexity of organizing such a formwork.

Reinforced concrete construction is assembled from individual slabs. The main advantage of this formwork is that its installation allows you to reduce the thickness of the foundation itself.

Metal. A metal mold is an excellent option when it is necessary to build a strip foundation. It is also used for monolithic structures. The indisputable advantage of this method is that, if desired, reinforcing concrete reinforcement can be welded directly to the formwork metal panels. This design is characterized by high strength and reliability.

Metal structures for formwork
Metal structures for formwork have one drawback – high cost

Note! Unlike formwork boards, the metal structure does not require the organization of additional struts.

Another advantage of the metal is its versatility. Such sheets can be bent, changing their shape as necessary. The disadvantage of this option is the high cost of construction.

DIY formwork foundation from improvised materials

For the assembly of formwork, not only specialized materials are used. For example, a small form for the foundation can be made from improvised means. It can be old doors, furniture parts, boards, slate, etc. The main advantage of this method is its cheapness.

It is worth noting that it is rather difficult to construct such a shape, since it is rather difficult to select the necessary details. It is very difficult to achieve the tightness of formwork made from improvised means. That is why this method is not popular. It can be used in the construction of a concrete fence. The form for fencing, made using this technology, requires consideration of possible problems that sometimes arise during operation.

special studs
To tighten the walls of the formwork, special studs are used

When using any materials, it is recommended to use special studs for formwork. They are necessary to tighten the walls of the structure. The rigidity of arbitrary formwork is much lower than this indicator of shapes assembled from specialized parts. When organizing this option, the risk of leakage of the solution increases.

It is recommended to take into account that in this case, you can not do without additional fasteners. To ensure good rigidity and stability of the structure, it is necessary to set special rails and supports. It should be remembered that such a method categorically cannot be used when organizing the foundation for residential buildings.

Laminated formwork plywood: material features

Laminated plywood is a traditional material used in the assembly of forming structures. This is due to the fact that it has the most suitable technical and physical characteristics. The lamination layer is located on the surface. Its function is to protect wood from moisture.

The surface texture of laminated sheets may be different. Allocate smooth and granular plywood. When choosing laminated sheets, it is first necessary to pay attention to their thickness, which can vary from 3 to 40 mm. The price per sheet of laminated plywood for formwork ranges from 21 to 56$. The cost depends on the type of wood from which the product is made, its thickness and dimensions.

Laminated plywood
Laminated plywood is a very convenient material for the construction of formwork

Note! For the assembly of forming structures, it is customary to use plywood with a thickness of 15 mm and above.

How to choose a formwork under the foundation? The most optimal option is sheets with a thickness of 18 to 21 mm. They are most often used in the design of formwork for the foundation and other building elements. Such products are characterized in that they can withstand high loads. Moreover, their mass allows for simple transportation and installation. Dimensions of standard sheets are 1250×2500 mm.

Formwork plywood: varieties of material

Today, there is a clear gradation of material such as plywood. There are several popular varieties of sheets that can be used as shields for forming structures. They all differ from each other in one way – the type of glue. When assembling formwork, the following types of plywood are used:

  • FBA;
  • FSF.

FBA In this case, an albuminocasein adhesive is located between the veneer layers. This type of plywood is highly environmentally friendly. It is often chosen as an alternative to natural materials. The price of plywood for formwork of this type is quite high, but it can even be used for surface cladding in residential premises.

For the organization of the forming structure, it is not recommended to use FBA, since this type of plywood is poorly resistant to moisture. Therefore, this option is used only as a last resort.

FSF. This material has good moisture resistance. This is a serious advantage that determines the operational features of such plywood. The bonding composition in this case is represented by a resin (phenol formaldehyde).

Many experts advise using this particular type of plywood when assembling the formwork with your own hands. For the walls, a slightly different technology is used, but for the foundation, this option is the most acceptable. Another advantage of the FSF is that it can be used several times. Sheathing the interior of the room with such plywood is not recommended.

How to make formwork under the foundation: features of the calculation

Before starting installation work, standard calculations are required. These include determining the amount of necessary material and finding its final cost. It is important to consider the type of raw material that will be used for the manufacture of formwork. OSB boards, plywood, chipboard, boards – all of these materials have different costs.

OSB formwork is most often used in private construction, as this material is not suitable for large projects due to poor resistance to moisture. The calculation of the number of boards is very simple. To do this, first of all, it is necessary to divide the perimeter of the planned foundation by the length of the wooden part. Next, you need to divide the height of the base by the width of the wooden board.

Formwork what is it
Expanded polystyrene blocks for formwork are very quickly mounted

The last thing to do is to multiply the two values ​​obtained earlier. The result will correspond to the number of boards that need to be purchased. Experts recommend adding a small margin to the calculated data (about 10%).

Note! One cubic meter of boards holds an average of 40 to 65 products.

In order to determine the cost, you need to multiply the price by the number of cubic meters of lumber needed to install the formwork foundation.

Other costs should be added to the figure obtained. For example, to assemble the forming structure, a certain amount of timber will be required. And also to strengthen the formwork, wooden spacers are used. The cost of purchasing additional materials may in some cases be 40-50% of the total price of plywood sheets and boards. The final cost calculation also adds the costs of acquiring tools and elements that will be used to fix the individual components of the formwork.

How to make a formwork for the foundation yourself (removable): preparatory stage

Before starting the assembly of the removable forming structure, it is necessary to purchase the appropriate tools and materials, and it is also worth preparing the territory that was determined for the installation of the foundation. The most common is a tape base. For the manufacture of removable formwork, the following materials will be required:

  • boards 100–150 mm wide and 25–30 mm thick;
  • spacer bars 100×50 mm;
  • stakes 40–50 mm thick;
  • wire;
  • nails
  • self-tapping screws;
  • a plastic film of sufficient density.

The calculation of materials for organizing the formwork of the strip foundation is based on the dimensions of the future foundation. It is necessary to take into account several requirements that allow the competent implementation of the formative structure. The height of the formwork assembled from plywood should exceed the base level by 50 mm. Spacers are installed at a strictly defined distance from each other (700-1000 mm).

It is important to remember that there should be as many stakes as there are side supports. Shields in the corners are fixed to each other. For this, side jumpers are used. When organizing the formwork, a dense film made of polyethylene material is used. It should cover the entire inside of the fence. Before you begin, it is recommended to watch instructional videos on how to properly make the foundation.

Preparation of the place where the base will be cast includes several types of work. First of all, you need to dig a ditch in the ground. The trench should match the design depth. At the same time, it is required that the width of the ditch has a margin of 10 cm greater than that of the future strip base.

Next, it is necessary to level and compact the earth at the bottom of the trench. Then, its walls are aligned. One of the most important conditions when filling the foundation is the organization at the bottom of the ditch of a special pillow made of gravel and sand. The standard width of this layer is 10-15 cm.

The most commonly used formwork materials are boards

Note! Not all buildings require foundation organization using a formative structure. In some cases, you can fill the foundation without formwork. Such a foundation is suitable for all kinds of temporary buildings. The technology of such construction takes into account digging trenches, laying polyethylene and reinforcing.

In the soil, which has a high density coefficient, a trench is made corresponding to the width of the concrete strip. Moreover, the formwork in this case should be located above the soil level.

Installation of a removable structure most often takes into account its reuse. If this is not necessary, then you can purchase a non-separable polystyrene foam form. It is quite difficult to do this work independently. To do this, you need to draw up a competent project and clearly follow the instructions for organizing the base formwork. Let’s consider each stage of work in more detail.

First of all, it is necessary to make shields, which are the main forming elements. Nails are used for fastening. The height of the shields should be slightly larger than that of the base (approximately 10 cm). In order to understand the features of the assembly of the forming structure, it is recommended to study the corresponding photos and videos. Do-it-yourself formwork foundation is strengthened by means of wooden stakes. As mentioned above, their step is approximately 70-100 cm. The distance from the foundation to the stakes should approximately equal 1 meter.

Next, you need to arrange the shields along the edges of the ditch and tie them with stakes, using special jumpers. Then the fence is aligned in a vertical plane, for which you will need to use the building level. After this, the structure is fixed to the mowing.

At the next stage, the inner cavity of the formwork is covered with a dense plastic film. The edges of the canvas are fixed using a construction stapler. Next, you will need to place a reinforcing lattice in the intermediate space. When installing the formwork for a strip foundation with your own hands, you may need to add wooden supports under the reinforcement, the height of which is 5 cm.

Note! Before filling, it is necessary to arrange passages for communications. For this, round sleeves are used.

After laying the reinforcing grille, plywood panels should be pulled together with a wire. It is worth noting that if the foundation has rounded zones, then in this case it will be necessary to bend the plywood in order to achieve the desired shape.

Basic requirements

During the assembly of the forming structure, it is necessary to observe certain requirements that are advanced to the dimensions. All possible deviations from the norm should be considered. Otherwise, an unstable form may result, which subsequently negatively affects the technical characteristics of the base. So, the manufacture of formwork is subject to special requirements.

How to make the foundation? It is important to remember that the deviation of the shield structure in the vertical plane should not exceed 5 mm per 1 meter of height. Quite often, inexperienced craftsmen make a mistake related to the location of boards in areas with a natural slope of the earth. The upper formwork board in this case should be located strictly horizontally. Repetition of the tilt is strictly not allowed.

Wall formwork
Wall formwork is not yet widely used in construction

There are also clear restrictions on the displacement of the forming structure from its original position. The maximum allowable offset is 15 mm. When installing the boards, you need to take into account that the differences between them should not exceed 3 mm.

How to put formwork on a site with loose soil? In this case, it is necessary to perform a wider ditch, on the sides of which additional struts need to be arranged.

If desired, at the stage of assembling the formwork, it is possible to warm the future foundation. To do this, use any suitable, inexpensive material (for example, foam). In this case, the trench expands in accordance with the indicator of the thickness of the insulating material.

In the case of organizing the foundation without formwork in the ground, suitable fittings are selected from which the lattice is constructed. It is not recommended to use such technology if the soil on the site does not have sufficient density.

When installing fixed formwork, it must be remembered that the most important criterion is its tightness. If we neglect this, then the insulating qualities of a non-separable structure will greatly decrease.

Fence formwork yorself: step-by-step instructions

The forming structure is used not only to fill the foundation of residential and farm buildings. The need for formwork is also present during the installation of some protective structures. The solid base of the fence ensures protection of the site from the penetration of unauthorized persons.

construction of the fence
The construction of the fence is not complete without pouring the foundation

Before starting the installation of the formwork in this case, you will also need to carry out some preparation. First of all, you need to mark the perimeter of the future design. Then, soil preparation is carried out, involving the removal of vegetation, stones, debris and other obstacles that may interfere with the installation of formwork under the fence.
Then you can start digging a trench. In this case, it is worth considering several rules. At points corresponding to the installation of support elements (columns), the depth should reach 80 cm. A similar indicator for spans is 50 cm.

Note! After organizing the trench, sand and gravel should be poured into it to prepare a special pillow .

How to build a formwork yourself under the foundation of the fence? At home, this device is not so difficult to perform. Even a person who does not have relevant experience can handle such a job. To organize the forming structure under the base of the fence, a phased algorithm of actions should be followed.

The first step is to strengthen the waterproofing qualities of the wood from which the formwork will be made. For this purpose, used engine oil is most often used. Next, the installation of vertical stakes. The distance between them should be no less than 50 cm, but no more than 1 meter.

Then, the support posts of the timber are mounted and the shields are fixed to them. For fixing in this case using ordinary nails or self-tapping screws. At the next stage, it is necessary to pull off the shield fence with wire and install a reinforcing mesh.

After mounting the fittings, the upper part of the frame is fixed. For this purpose, wooden blocks are used. In the corners are staples that perform a mounting function. At the final stage, it will be necessary to close the cracks in the structure. This completes the installation of the formwork for the base of the fence.

Self-installation of formwork foundation of a residential or utility building requires serious preparation. In addition to drawing up a plan, a calculation should be made of the amount of materials needed. Before assembling this design, it is recommended to study all possible video materials on this topic.


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