Not so long ago, in the field of domestic housing construction, the technology of fixed formwork began to be mastered. It involves the construction of a foundation based on lightweight materials that are not removed after installation, in contrast to the classic formwork structure made of wood. The most common method of arranging fixed formwork made of expanded polystyrene. For the foundation of a thermal house, this is the optimal solution that improves the heat-insulating and shaping qualities of the structure. But there are also negative factors in the use of this technology, which will also be discussed below.
Design of fixed formwork
If in a traditional wooden formwork the base performs only a temporary solution-retaining function, then the expanded polystyrene forms a vertical partition, in the niches of which andconcrete is poured. The thickness of the walls is on average 5 cm, and the distance between the individual structural elements reaches 15 cm. As for the height of the foundation formwork of this type, it can vary from 50 to 250 cm: it is important to keep in mind the possibility of building walls. Even after the foundation of the foundation is completed, the panels, according to the principle of the designer, can be led up to the roof itself. But this solution must be provided in advance in the project, since special jumpers are selected for it at the level of the grillage, where the ceiling and foundation converge.
From the point of view of insulating properties, fixed formwork performs the function of a thermos. For this reason, houses on such a base are also called heat-saving. By itself, the design of the formwork made of expanded polystyrene is characterized by good sealing, but this has a drawback. It consists in the need to install ventilation ducts that exclude the accumulation of condensate, which negatively affects the state of the cement slurry. On the other hand, there is no need for additional insulation of the foundation.
What is Styrofoam?
This is a kind of composite building material, the shape and parameters of which are specially adjusted to the requirements of fixed formwork. In other words, these are the elements that form the mold for pouring foundation concrete. They can be made in the form of blocks, perforated slabs or large format panels. All types of parts are combined by similar technical and structuralopportunities.
Here we need to understand what is polystyrene foam for the foundation in a functional sense? This is a structural element that provides a strong reinforced frame and performs a number of insulating tasks. Increased stability of the structure that holds the concrete form is achieved by jumpers or ties that bring the parallel elements of the frame together. At the same time, a technological gap for communications is provided in each masonry.
Pros and cons of Styrofoam
The material is quite technologically advanced and specially oriented for use as a formwork element. This assignment brings a number of attractive operational factors, such as:
- high heat and sound insulation qualities;
- no need for additional reinforcement of the structure due to columns and metal bandages, since the expanded polystyrene itself is quite strong;
- variety of form factors and sizes makes it possible to implement a wide variety of design variations when creating strip footing contours;
- ease and speed of erection.
It is worth noting that the formwork for the foundation of expanded polystyrene also has weaknesses, which are especially evident against the background of other products designed for the same tasks:
- The material is sensitive to moisture, so waterproofing measures are a must. The same applies to vapor permeability.
- In Styrofoam structureit is impossible to introduce hardware and mounting elements that do not correspond in format to the originally provided factory holes and grooves.
- Some modifications of Styrofoam support combustion.
- There is evidence that the material can be destroyed by rodents.
- High cost. The average price for 1 m2 of expanded polystyrene in the form of blocks is 700–1,000 rubles. The thickness of the walls in this case can be from 5 to 10 cm.
If we talk about alternative materials to expanded polystyrene, then they include cement, chip-cement, foam plastic and wood-fiber products. They are also produced in different structural and dimensional formats, but have different technical and operational properties.
Installation of formwork for the foundation of expanded polystyrene
The design is formed by assembling block or panel elements on a site prepared for installation. Throughout the process, it is important to observe the correct position of the walls vertically and horizontally - for this, a construction level is used. Elements should be laid out starting from the corners by fitting onto the reinforcement. It is important that the same position of the grooves is maintained along the entire vertical - horizontal reinforcement will continue to be laid in them. Also, for the purpose of local power bonding, plastic formwork ties are used. They connect the two sides of the panel, forming a hollow box in which it will be possible to lay communications. The groove system, in turn,seals and fixes technological joints, eliminating the possibility of divergence of seams and the formation of cold bridges.
Filling the structure
After assembling the formwork structure, concrete is poured into the prepared niches. This applies to the tape configuration of the foundation, but the technology of a monolithic carrier base is also quite applicable, when the entire area between the walls of expanded polystyrene is poured with mortar. In both cases, the concrete that has not yet hardened is equipped with reinforcing bars with a diameter of at least 10 mm. In the future, they will have to combine the base of the foundation and the formwork box into a monolithic reliable platform.
Finishing the foundation with formwork
The external cladding will have two functions - to improve the appearance of the formwork and protect it from external negative influences. Immediately it should be noted the advantage of expanded polystyrene, which consists in its almost ideal geometric shapes. Therefore, the need to align the walls of the structure simply disappears. You can immediately proceed to the external reinforcement and laying the decorative layer. It is possible to strengthen the formwork surface with stainless mesh or fiberglass. These are thin reinforcing coatings that can be sealed with a plaster composition. This is followed by decorative putty with suitable textured qualities. Another interesting finishing option is allowed with the use of metal formwork ties that go outside, allowing you to mount heavy external coverings. Bows provide additional bearing force, due to which the blockspolystyrene foam can be used to fix ventilated facades or siding subsystem.
Advantages of technology
If we compare a polystyrene formwork structure with a conventional wooden assembly, then there will be a lot of pluses - both in functionality and in technical properties. The most significant strengths of the formwork for the foundation of expanded polystyrene include the following:
- combination of strength and lightness of construction;
- high assembly speed;
- variety of wiring diagrams;
- high insulating qualities;
- no need to dismantle the formwork after the foundation.
Flaws of technology
If the advantages of the design are mainly expressed in its technical qualities, the disadvantages are due to the sensitivity of the material to external factors. As already noted, the blocks can be subjected to combustion, destruction under conditions of contact with moisture and in unfavorable biological environments. A serious drawback is the price for 1 m2 of expanded polystyrene, which is about 1,000 rubles. In the final estimate, this means that formwork for a house with an area of 100 m2 or more2, together with mounting hardware, will cost about 70-80 thousand rubles.
Conclusion
Determining the choice of the foundation base construction method, it is desirable to formulate the requirements for it in detail. Expanded polystyrene is good becauseexpands the capabilities of the prefabricated frame, but at the same time sacrifices some of its usual qualities. For many, the decisive factor is the ability to assemble the structure with their own hands. Expanded polystyrene formwork for the foundation does not require the use of special equipment for installation. All fasteners are formed with the usual set of home craftsman tools. The only difficulty will be the need for accurate calculations and constant monitoring of the installation positions of the formwork elements using levels and levels.
