Do-it-yourself fixed formwork for a strip foundation. Strip foundation with fixed formwork

Today, construction technologies are progressively developing and improving every day. Innovative developments penetrate into all technological stages of the construction of various buildings. Of course, a special area of ​​construction, where new materials and techniques are especially relevant, is the creation of foundations.

Any building (residential building, office complex, etc.), after drawing up and accepting an engineering project, begins with the construction of the foundation. In the old fashioned way, it is still quite often made with formwork made of wooden panels or boards, but current technologies make it possible to regularly use innovative methods, among which permanent formwork made of various materials is considered the most promising.

Let's take a closer look at the types, features, application, assembly of permanent formwork for the foundation and much other thematic information.

Permanent formwork - general information

Permanent formwork is a built-up shaped structure used in modern construction for the construction of foundations or load-bearing walls of some buildings.

Outwardly, it looks like a single, strong structure made of blocks or panels. After assembling the structure, a cement-sand mass is poured into its interpanel space, which, after hardening, forms a concrete frame monolithic foundation.

Advantages of permanent formwork

The use of monolithic formwork in the construction, which allows you to create a strong, reliable foundation (or walls), has many worthy advantages:

— acceleration of the process of laying materials and building the necessary structures;

— lightening the overall weight of the structure due to the possibility of reducing wall thickness;

— providing excellent sound and heat insulation;

— permanent formwork can be used in almost any construction project - typical one- or multi-story residential buildings, complex retail and office structures, unusual sports and entertainment facilities, etc.;

- it is possible to use modern materials for such formwork (for example, wood concrete, reinforced polystyrene, expanded polystyrene) in any climatic conditions - there are no restrictions;

- decorative function - the formwork can have a structured or molded front surface, which will eliminate the need for additional decoration of the facade with special tiles or panels.

Disadvantages of permanent formwork

The most significant disadvantages of the construction technology under consideration include the possibility of its use only for the construction of foundations. There are, of course, technologies for low-rise wall construction using permanent formwork, but they are very expensive.

Read also: How to protect yourself from noise: soundproofing an apartment

For example, you can build walls above the foundation using lightweight glass-magnesite formwork, which is filled with a special foamed concrete solution. This is how a maximum of two-story houses with walls made of foam concrete are created. Such construction is very expensive due to the high cost of materials and the hiring of special equipment and experienced specialists.

Types of permanent formwork

It was previously noted that permanent formwork, depending on the project, can be constructed from many different materials. The most commonly used are the following varieties:

1. Foamed polystyrene with internal voids– the material is presented in the form of layers (plate plates), connected into a solid structure using special jumpers. The structure being built resembles a Lego set, in which blocks are connected into a variety of large shapes. As a result, after pouring the cement-sand mass, monolithic polystyrene concrete is formed, which requires external (external) and internal finishing. The lining is mainly necessary to protect the material.

2. Armopanel– available in different versions – Paroc board, polystyrene foam or Rockwool, covered on both sides with metal mesh. During installation, concrete is poured under pressure between the panels. Once the solution has hardened, a kind of “sandwich panels” are formed, which are particularly durable. This construction method is considered to be low-budget, providing excellent performance.

3. Fixed decorative formwork- This is a structure characterized by the presence of a finished outer cladding. Its assembly is carried out using the method of seamless laying of special blocks.

Important! In this version of permanent formwork, you need to put some kind of heat-insulating material (expanded polystyrene or layers of mineral wool) between the walls of the structure!

After preparing the formwork, concrete mixture is poured into it. The result is a monolithic, insulated concrete structure with decorative finishing.

4. Wood concrete (wood concrete panels or blocks)- These are slabs consisting of sawdust mixed with wood chips and cement. The formwork is assembled using ties, long screws and nails. Often, when building in a cold climate, a heat-insulating polystyrene foam liner is installed in it. Then reinforcement or other metal rods are placed and concrete-sand mortar is poured into the prepared structure.

The external surface requires decorative finishing with clinker, facade plaster, siding or natural stone. The inside can be finished with plasterboard or plaster mixture.

Read also: Technology for arranging a “wet facade” in a house (photo). Advantages and disadvantages of a wet facade

More information about polystyrene foam formwork

It’s worth stopping and considering the polystyrene foam version of permanent formwork, since it is the one that is most often used in construction today.

The key reason for its popularity is the simplicity and ease of installation of polystyrene foam boards. The work absolutely does not require the involvement of qualified specialists or any equipment. The block wall elements are firmly fastened together, and then concrete is poured into the formed space.

Various communications are laid in pre-designed technological openings. With this installation method, an insulated reinforced concrete wall with a monolithic structure is obtained.

This design does not require any additional sound or heat insulation work, since polystyrene foam performs such functions perfectly. In addition, the surface of this material does not absorb moisture and does not allow water vapor to pass through it at all. For a monolithic foundation with fixed polystyrene foam formwork, unfavorable weather is not a problem.

The advantages also include the resistance of expanded polystyrene to cracking and thermal structural expansion - that is, this technology can be used to build houses in hot, earthquake-prone regions.

The structure of permanent formwork, assembled from polystyrene foam boards, is simple and consists of the following parts:

— plastic ties;

— steel (galvanized) L-shaped hooks designed for strong fixation of plastic ties;

— external and internal facing decorative plates. They are made from concrete mixture and have a beautiful external structure.

General principles and features of installation of permanent formwork

The construction of a foundation using the technological method of permanent formwork is not difficult, although it consists of several successive stages, which are characterized by specific features. Let's look at them in detail:

1. Preparation of land at the construction site

The created monolithic foundation, directly depending on the functional purpose of the building under construction, can be directly laid on leveled ground or in a dug trench. Although, regardless of the chosen method, during installation, under the lower surface of the foundation, a sand and gravel “cushion” with a thickness of more than 11.0 cm should be poured. Such a carefully compacted layer effectively compensates for the expansion of the soil and small displacements of its layers due to changes in temperature or changes in groundwater levels.

2. Installation of permanent formwork structure

Since the design process (design and installation) of permanent formwork is very simple, especially from polystyrene foam material, it is accessible even to untrained workers. The main thing is that the employee has minimal skills in construction and technological production.

Permanent formwork made of lightweight materials is installed according to the principle of a children's construction set or classic brickwork.

Construction technologies are developing every day. They penetrate into all stages of building construction and, of course, have not ignored the area of ​​foundation construction.

The construction of each building after drawing up the project begins with the construction of the foundation. Very often it is made with wooden formwork, but modern technologies allow the use of innovative methods and the use of permanent formwork. What is it and how to build a foundation using permanent formwork with your own hands?

The method of building foundations using permanent formwork was invented and began to be implemented about 15 years ago. At the same time, all the main stages of foundation construction remain the same; there are changes only at the stage of formwork formation. Let us briefly recall how a monolithic concrete strip foundation is erected.

What should you consider when constructing formwork for the foundation?

At the beginning of every foundation lies a project. The calculation of the foundation structure is made based on two main conditions - the bearing capacity of the soil of your site and the gravity of the building being erected. Depending on this, the area of ​​the base and the grade of concrete used are calculated.

After calculating the foundation, the construction site should be cleared and marked out. This is a very painstaking work, since the geometry of the entire building being constructed depends on its correct implementation.

The classic concrete strip foundation is laid in formwork, which, in turn, is placed in a trench dug in the ground. Sand and crushed stone cushions are laid successively at the bottom of the trench.

And here the visible differences between removable and permanent formwork begin. Removable formwork is a rather complex carpentry structure consisting of many elements. In order to build it correctly, you need to have solid technological skills.

But permanent formwork is assembled simply, like the famous children's Lego set. In addition, permanent formwork does not need to be dismantled, since it plays another important role in the foundation - it is a thermal insulation layer. In classic formwork designs, thermal insulation has to be laid additionally - at the next stages of work. When using permanent formwork, you get “two in one”, that is, a limiter for the concrete solution and a layer of thermal insulation.

Naturally, using permanent formwork does not relieve you of the need to build a reinforcing belt inside the formwork. They are made of metal rods connected into some kind of cage. The rods at the intersection points are welded together or connected with knitting wire.

One of the advantages of permanent formwork is that it does not absorb water at all. This way you can be sure that the correct proportions of the concrete solution being poured are maintained.

As a thermal insulator, some types of permanent formwork are protected from fire, and they are also extremely resistant in humid environments.

But we can also note the disadvantages of this design. First of all, it is expensive. But at the same time, it is worth remembering that by using permanent formwork you can save on the thermal insulation layer.

Video - foundation using permanent formwork part 1

Video - building a foundation using permanent formwork part 2

Types of permanent formwork

Designers have developed several types of permanent formwork. Let's take a look at what the modern construction industry can provide you with.

The classic type of permanent formwork is polystyrene foam boards. Despite their lightness, they are quite durable, are excellent heat insulators and at the same time do not interfere with the necessary air circulation.

The next type are forms made from a mixture of wood chips and cement. This type of permanent formwork boasts excellent sound insulation properties. To retain heat, such slabs have small air bubbles between the wood chips. Despite the fact that the design uses essentially short-lived wood, its special processing allows such a slab to retain its qualities for a long time. In addition, such specially treated wood chips do not ignite and do not absorb moisture.

Fiberboard permanent formwork is a product of the chemical industry. It consists of magnesite, which is mixed with wood shavings. If magnesite is replaced with Portland cement, then such a slab essentially repeats the previous design. This type of permanent formwork has excellent fire resistance; such slabs serve as a reliable barrier to steam and retain the heat of your home well.

Construction technologies using permanent formwork

In addition to the construction of foundations, permanent formwork is also widely used in the construction of walls. Moreover, in some cases such use is the main one.

So, in order to build a wall using permanent formwork, it must be installed on a waterproofed foundation. The slabs are fixed to the reinforcing bars left protruding from the foundation. These rods serve as the basis for the formation of new rows of reinforcing mesh, while adjacent rods must be overlapped.

When installing the first row of permanent formwork, carefully check the locations of future doorways and the junction of internal walls.

Next, gradually increase the grid of reinforcing bars and both walls of permanent formwork. In fact, you are preparing the basis for creating a kind of sandwich - a structure where two layers of heat-insulating material will be limited to a concrete casting with a metal frame.

When pouring concrete into permanent formwork, the same technologies should be used as when forming any concrete casting. It is advisable to fill the entire volume at one time. If this does not work, then concrete must be laid in layers. In any case, the raw concrete mass must be processed to prevent the formation of air voids in its thickness. This can be done either with the help of specialized equipment - deep vibrators, or simply by piercing the mass of concrete with a sharp object.

If you are building concrete walls with permanent formwork, then during their construction you also need to carefully monitor the places where utilities are connected and the formation of building structural elements. It is best to lay out the places for their penetration or construction in advance, so as not to chisel the hardened concrete later.

If you purchase high-quality, elastic blocks of permanent formwork, carefully prepare fasteners and securely fasten the installed structure, then building a foundation or walls with permanent formwork can be a fairly affordable process.

The use of permanent formwork in construction, including for construction, provides certain advantages, among which we should highlight speed of work, which can be carried out, following technology, even all year round. It is also possible to simultaneously make a thermal insulation layer, the thickness and characteristics of which, in most cases, are quite sufficient and some others. But, due to the rather high cost of permanent formwork, which can be made from different materials, this method has not been widely used.

Peculiar The revolution was made by the appearance of polystyrene foam blocks, the cost of which, although not low, is due to the effect obtained from their use, their use is completely justified.

Scope of application of polystyrene foam blocks for formwork

Blocks for permanent formwork are products that can have not only different sizes and shapes, for example, intended for walls, corners, as well as for creating various architectural elements, but also to be solid or collapsible. The second type is most often used in cases where it is necessary to erect a wall or foundation structure with a given thickness.

To connect the blocks to each other, a tongue-and-groove connection is used, and reinforcement is first installed into the hollow space, and then the concrete mixture is poured. Additional strength of the future building structure is also provided by metal jumpers located inside the block, but they primarily provide the rigidity of the block when pouring concrete.
Expanded polystyrene permanent formwork can be used for the construction of vertical structures, for example, for the construction of low-rise buildings, on average 3-4 floors, but this material is most popular for constructing strip foundations for such houses. As a result, the foundation receives additional strength of the monolithic structure, which also has a heat and waterproofing layer.

Marking of blocks, their types and sizes

It should be taken into account that the marking indicates the future thickness of the structure, in this case, the foundation. The height of the products varies from 10 to 50 cm, so when choosing a material, blocks of different sizes are often combined to produce formwork of the required height.

The blocks can be different, but the average size is 1000x300x250 mm, with 8 jumpers, and its weight is about 1.5 kg. The blocks can also be distinguished by the type of their internal section: there are H-shaped and U-shaped, the latter have an additional (lower) side made of polystyrene foam.

For the convenience of supplying communications and making corner connections, products of a certain shape are produced, with prepared holes. Blocks are produced from both ordinary polystyrene foam and extruded with improved characteristics.
Why, when constructing a strip foundation, does it make sense to give preference to permanent polystyrene foam formwork?
In order to gain popularity, any material must have unique or additional qualities and characteristics that give it an advantage over its analogues, and polystyrene foam blocks have quite a lot of them, especially when constructing a foundation:

  • the ability to build a foundation with increased load-bearing capacity and geometrically ideal shapes;
  • no need for supports or struts;
  • when pouring concrete, you should not be afraid of the expansion of the formwork and especially the leakage of the solution;
  • permanent formwork takes on additional functions - a heat and waterproofing layer and does not require additional or the use of similar materials;
  • the installation technology is simple, and the ease of performing the work is ensured by special tongue-and-groove connections of the blocks, which ensure the highest possible assembly speed, which is also facilitated by the fairly large dimensions of the products;
  • Even a beginner in construction can perform installation, and most operations can be performed even alone;
  • Thanks to the design features and the presence of special technological holes in the blocks, installation of communications is greatly simplified.

If we compare the cost of formwork for a foundation made of polystyrene foam blocks and from traditional plank or plywood panels, then the second option will have an advantage. But if we take into account the future benefits from the operation of an object built from permanent formwork, as well as the quality of construction of the object itself and its characteristics, then polystyrene foam formwork will definitely win this competition.

Disadvantages of permanent formwork

But when choosing permanent formwork made of expanded polystyrene, you should also be aware of the weaknesses of this material in order to, if possible, take measures to eliminate the occurrence of negative factors.

So, what is most objectionable about this material:

    • the durability of polystyrene foam is on average 20 years, therefore, after this period, a monolithic structure New heat and waterproofing will be required. You should also be prepared that performance characteristics will gradually decrease during this time. Finishing the surface of the walls helps to slow down the process somewhat, which should be carried out as soon as possible after construction;
    • the problem of thermal and waterproofing of the “sole” of the foundation, which forms not a bridge of cold, but a large, real “bridge” of cold. The use of blocks with a U-shaped cross-section helps to avoid this problem somewhat;
    • pouring concrete has some features that, despite the simple formwork installation technology, can significantly slow down the process - concreting should be carried out in equal layers along the entire perimeter, which is quite difficult to ensure due to the small size of the blocks for this operation;
    • environmental friendliness of the material containing styrene, which has the ability to evaporate, especially in warm conditions. To avoid health hazards, it is necessary to purchase high-quality products that contain minimal styrene, in an absolutely safe concentration;
    • the price can also be a disadvantage, but since everything is learned by comparison, before making a final decision, it is necessary to make a full comparative analysis, especially with traditional removable formwork made of boards;
    • there is no consensus, even among experts, on the effect on the strength of a monolithic base made of blocks with internal polystyrene liners.

There is also no unequivocal opinion on the installation of fixed formwork for strip foundations in climatic zones with a deep level of soil freezing, it is recommended in such cases to give preference to high-quality products with improved characteristics.

Installation

Before proceeding with the installation of the formwork, it is necessary, first of all, to prepare a trench on a leveled area, and then, with the upcoming amount of work, a small team of 2-5 people or even beginners in construction will be able to handle the upcoming amount of work.

  1. A gravel-sand cushion is laid at the bottom of the trench or a thin cement screed is made.
  2. The next step is the laying of a waterproofing layer, on which the first row of blocks is installed.
  3. The first row should be laid not only neatly, but also as accurately as possible, and special rotary blocks should be used to connect the corners or mounting foam should be used.
  4. When installing polystyrene blocks for formwork you should use special elements, greatly facilitating the process: various shapes and purposes with plugs, modules, additional products.
  5. Laying the second and subsequent rows must be done with an offset.
  6. Reinforcement should be pulled through the internal through cavities of interconnected blocks.
  7. All blocks must be tightly connected to each other using a tongue-and-groove lock.
  8. To pour one layer of concrete, it is necessary to prepare a formwork of no more than 3-4 rows, otherwise it will be quite difficult vibrate the solution, which can lead to the formation of voids, especially dangerous around fittings.

Price

Due to the fact that the production of polystyrene blocks for formwork is not unified, products of various shapes, types and sizes are presented on the market. But if we talk about their cost, then we can focus on the following data:

      • the price of a standard block, for example, with dimensions of 1250 × 250 × 250, 1000 × 300 × 250 or similar, ranges from 250 to 500 rubles;
      • corner blocks cost from 190 to 500 rubles;
      • the cost of end blocks reaches 750-800 rubles;
      • wall price from 270 to 800 rubles;
      • one module for making a jumper will cost 350-500 rubles;
      • the cost of partitions, plugs, end connections starts from 10 rubles and can reach 100 or more rubles (depending on the type of element).

Manufacturers

The production of polystyrene foam blocks is a rather complex and high-tech production, but despite this, the Russian market offers high-quality products produced in different regions of the country. Among Russian manufacturers, the leading positions are occupied by:

      • CJSC "PKP" Warm House", the production of which is located in the Moscow region, in the Lyubertsy district;
      • LLC "My House", Rostov-on-Don;
      • LLC "DSM-Stroy" - whose production facilities are located in the Urals, in Chelyabinsk;
      • LLC "Timal", Ufa

Before buying blocks, you should try to get maximum information about discounts, delivery methods to the site, and its cost. Some manufacturers and their distributors may offer seasonal discounts, for example, during the winter months.

To make a monolithic strip foundation with your own hands, you will need to select a form for pouring the mixture. One option is permanent formwork for the foundation. In addition to its main function, this element can play the role of additional protection of the supporting structure during operation.

Any form for the construction of a monolithic foundation is made according to GOST “Formwork. General technical conditions". It is recommended that you read this document before starting construction. When purchasing permanent formwork, special attention should be paid to the following points of the standard:

  • Basic quality parameters (point 5);
  • General technical requirements (clause 6);
  • Acceptance rules (clause 8);
  • Transportation and storage (clause 10).

Depending on the raw materials for making the mold, the following product options can be given:

  • from expanded polystyrene;
  • from cement-bonded particle boards;
  • from wood concrete;
  • from fiberboard.

To understand which option is suitable in each individual construction case, it is worth considering them separately.

Expanded polystyrene

The materials are made from styrene beads. Depending on the manufacturing technology, there are two types, different in properties:

  • Styrofoam;
  • extruded polystyrene foam.

Ready-made permanent foam formwork modules.

The advantages of the first include:

  • low cost;
  • good thermal insulation characteristics;
  • resistance to rotting and damage by various microorganisms;
  • ease of transportation and installation due to the low weight of the products;
  • high speed of mold production.

The disadvantages are low strength, inability to maintain a solid shape while being exposed to moisture and cold (water penetrates into the space between the balls and expands when freezing, the material crumbles). The material decomposes when exposed to direct sunlight and is often damaged by rodents.

Advice! To build a strip foundation, it is better to invest a little more financial resources and choose extruded polystyrene foam. It has higher strength and resistance to adverse influences, which means the material will last longer. You can distinguish two materials of similar origin visually: polystyrene foam is white, and its closest relative is colored (orange, blue, gray, etc.)

Fixed formwork made of extruded polystyrene foam.

In terms of manufacturing technology, there are also two options:

  • assemble formwork from sheets of standard sizes;
  • buy ready-made blocks.

The second method is more convenient. Expanded polystyrene blocks already have vertical panels and jumpers between them. There are both regular and corner products. The structure is assembled according to the principle of a designer in the shortest possible time.

Cement particle boards

The use of DSP as panels for making molds for pouring strip foundations has been common for quite a long time. This material consists of cement and wood shavings. The first component ensures the preservation of the given shape and compressive strength, while the second increases the bending strength.

DSP formwork.

The slabs are installed in a vertical position and connected to each other by jumpers (wooden or reinforced). The use of DSP as a mold for filling has the following advantages:

  • strength;
  • a decrease in the ability to conduct heat due to the inclusion of wood chips in the composition (but this material should not be considered as a full-fledged insulation);
  • impact resistance;
  • wide operating temperature range;
  • ease of finishing the base (the simplest option would be plastering on DSP boards).

It is important to note that experienced specialists recommend using such forms only on stable soils, which means that it is not advisable to install them on swampy or bulk soils. This is due to the fact that wood quickly loses strength when exposed to moisture. The thickness of the slab is quite small, and if pores (voids in the place of damaged chips) occur, it is difficult for the slab to keep its shape and maintain strength when soil movements occur and concrete is poured.

Another disadvantage is that the thermal insulation of such formwork is much lower than that of expanded polystyrene. The thickness of the plate is in the range of 16-24 mm.

Arbolit

This option is similar in composition to the previous one. It is also based on a concrete mixture and wood chips (shavings). The method has recently become increasingly popular. As in the case of expanded polystyrene, the form consists of ready-made blocks that only need to be assembled at the construction site into a solid structure.

Wood concrete formwork.

Permanent wood concrete formwork has the following advantages:

  • increased thermal insulation properties;
  • resistance to moisture (but this does not apply to underground structures);
  • maintaining characteristics at high temperatures.

The disadvantages include the large mass, which causes inconvenience during transportation and installation. Most often, this option is used only for filling the base.

The material is similar to the previous two options. The main component here is Portland cement M500 or caustic magnesite, and the filling is wood chips or shavings. The advantages of this manufacturing method include:

  • increased soundproofing and thermal insulation characteristics;
  • biological stability in a dry state;
  • easy to process;
  • small weight;
  • reduction of labor costs and construction costs;
  • simplicity of finishing the base.

Fiberboard board.

In terms of weight, fiberboard, like all the above materials, loses to expanded polystyrene. It is important to know that resistance to biological effects is maintained only at humidity levels up to 35%. When exposed to water, there is a possibility of damage by mold or fungus. When used as a form for the foundation, it is especially necessary to worry about sufficient waterproofing of the fiberboard, as well as the two previous formwork options, because. their base is wood.

Permanent formwork technology

The process depends on what products are used. Everything is much simpler if ready-made volumetric blocks are used. The slabs will require a lot of labor. Here the most difficult thing is to install the first row, the fixation is carried out with metal brackets. Next, the shields are assembled and connected to each other with wooden jumpers. If the material is not strong enough to withstand the concrete mixture, then it will be necessary to provide a support system from the outside (relevant for high formwork, from 30 cm and above).

  1. After mounting the mold, before pouring the concrete mixture, you need to install branch pipes for engineering communications. To do this, holes are drilled in the deck for network inputs into the building.
  2. performed at positive temperatures (more than +5ᵒC).
  3. The main means of fastening are formwork nuts and clamping screws. You should prepare them in advance. You can use studs, regular nuts, and wood blocks with a hole.
  4. The front is placed in the mold. This is necessary to prevent the leakage of cement laitance and reduce the strength of the foundation.
  5. The top layer of formwork is filled only to half the height. Thanks to this, the concrete joint between the pouring layers is inside the block.

Formwork made from extruded polystyrene foam is the best option, since it produces both formwork and full-fledged insulation that is resistant to moisture and aggressive environments, with a long service life. But it is important to remember that it is not enough to choose the right formwork; you also need to take care of the reinforcement and concrete mixture, their correct choice, appropriate quality and further care of the concrete in the process of gaining strength.

Formwork is an auxiliary prefabricated structure designed to form the correct geometry of concrete walls. For its construction, materials are used that do not absorb moisture and can withstand the pressure of liquid concrete during pouring and compaction. Once the concrete mixture has hardened, the formwork can be dismantled for reuse or left in place. In the second case, the formwork structure is called permanent.

The decision to leave the formwork without dismantling it after finishing concreting can be justified:

  • impossibility of carrying out dismantling work;
  • inappropriateness of dismantling;
  • using enclosing material as a thermal insulation layer and waterproofing;
  • the need to strengthen the concrete structure.

In the last two cases, the material for formwork is selected in advance and used as a building structure, performing certain design functions.

Eps formwork.

Advantages and disadvantages of permanent formwork systems

The main advantages of using concrete permanent formwork for the foundation when constructing reinforced concrete monolithic structures include:

  1. the ability to provide good thermal and hydraulic insulation;
  2. simple assembly technology;
  3. absence of a dismantling stage;
  4. obtaining a smooth outer surface;
  5. minimizing the amount of construction waste;
  6. increase in service life;
  7. versatility of use for various structures.

Experts include the following disadvantages of using non-removable technology:

  1. increased costs due to the use of additional materials;
  2. reduced vapor permeability of the building structure;
  3. the need for gradual pouring of concrete mixture;
  4. complicating repairs or reconstruction in the future.

Comparing the pros and cons, we can say that the main controversial issue of this technology is the increase in the cost of construction. But a concrete strip foundation during its construction still requires the installation of an external waterproofing layer, and in the presence of a basement or semi-basement, wall and blind areas are often insulated. Both of these issues can be easily solved by using moisture-resistant durable insulation to assemble the formwork structure.

Basic system requirements

Materials for formwork systems of this type must meet the following requirements:

  • mechanical strength to withstand the pressure of the concrete mixture and the load from the soil during operation;
  • moisture resistance of the layer and tightness of joints;
  • precise geometry of individual elements with a flat surface;
  • long service life without changing technical characteristics;
  • simple installation technology;
  • relatively low cost.

It is also worth mentioning the necessary availability for purchase in a regular market sale.

Materials used for permanent formwork

The choice of the main formwork material depends on the technical purpose, cost and complexity of the foundation structure. In practice, for permanent formwork systems the following is used:

  • extruded polystyrene foam;
  • cement particle boards (CSB);
  • wood concrete;
  • glass magnesite;
  • sheet metal.

In addition, moisture-resistant plywood and fiberboard are used, but due to the fragility of these materials when used in the ground for foundation structures, they are used extremely rarely, and only to speed up installation.

Expanded polystyrene formwork

Dense extruded foam plastic is the most popular material for permanent formwork when constructing monolithic strip foundations. The high level of demand is explained by:

  • sufficient strength and moisture resistance;
  • light weight and ease of processing;
  • the presence of a tongue-and-groove system for connecting individual elements;
  • low labor costs during installation;
  • excellent heat, sound and waterproofing properties;
  • the presence of reinforced and coated slabs;
  • biological inertness, preventing the formation of mold and mildew;
  • durability.

Opponents of the use of permanent formwork for polystyrene foam foundations point to its instability and danger in case of fire, as well as the low level of environmental friendliness. However, for the underground part of the foundation, exposure to flame during a fire is practically not dangerous, and for the same reason no environmental damage can be caused, especially if the outer surface is covered with a protective layer.


Formwork blocks made of EPS.

The only important drawback is the lack of corner and rounded elements on sale. This limits the use of the material in the case of installation of formwork of complex configuration.

Cement particle boards

DSP is produced by mixing crushed wood with cement-sand mortar and pouring the mixture into flat molds. This is a fairly dense, durable and heavy material. The presence of wood chips in its composition increases the thermal insulation properties, but there is no great efficiency in this matter. Among the main advantages of using cement bonded particle boards, we can point out that this material:

  • has good vapor permeability and does not create a greenhouse effect;
  • fireproof and has a high level of fire resistance;
  • has high strength, which helps strengthen the foundation structure;
  • made from environmentally friendly raw materials;
  • resistant to sudden temperature changes over a wide range;
  • affordable for most developers;
  • requires minimal finishing, consisting of additional sealing of joints.

The main disadvantage of cement particle boards is their moisture permeability. Therefore, when constructing strip foundations, the underground part of the formwork must be covered with coating or roll materials on a bitumen basis to enhance the waterproofing properties.

The practice of using DSP as permanent formwork has a 25-year history. And we can say with confidence that this material is durable and reliable.

Arbolite blocks

Arbolite is a relatively new option for using cement-bonded particle board mixtures. From them I make hollow blocks from which the formwork structure is assembled. When making wood concrete, in addition to cement and wood shavings, crushed straw, sawdust and plasticizers can be added to its composition.


Scheme of formwork made of wood concrete and brick.

After installing the blocks, their internal cavities are half filled with concrete, reinforcing bars are laid and concrete is added to the upper level. Arbolite blocks are much cheaper than high-quality reinforced concrete and therefore this type of permanent formwork is widely used in private low-rise construction for the construction of foundations and walls of buildings. The advantages of wood concrete include:

  • possibility of simple mechanical processing during installation;
  • performing work without the use of special equipment and special tools;
  • high strength and improved thermal insulation properties compared to concrete;
  • environmental safety and recyclability;
  • resistance to flame and high temperatures;
  • good frost resistance.

The disadvantage of arbolite blocks, like those of DSP, is moisture permeability and the need to install a waterproofing layer.

1. Pillow lightly poured with concrete mixture.

2. First row.

3. Reinforcement.

4. Second row.

5. Filling.

Fibrolite

This is another option for making blocks based on a cement-sand mixture. But in this case, long strips of wood, cut along the fibers using special equipment, are used as filler. The material has the same properties as arbolite blocks, but is much stronger. This allows it to be used as permanent formwork when constructing foundations for two- and three-story buildings.

The need to use special equipment for producing wood fiber and increased requirements for raw materials make fiberboard a more expensive material compared to wood concrete and fiberboard. However, its use still makes it possible to reduce the overall costs of constructing strip foundations.

Glass magnesite

Glass magnesite sheets or FMS are made from a mixture of magnesium compounds, perlite, fiberglass, polypropylene and sawdust. Despite the fact that not all components are of natural origin, finished materials are environmentally friendly. These slabs were developed and manufactured in Asian countries. Domestic enterprises do not produce glass-magnesite boards.

LSU is an excellent option if you need to strengthen the foundation structure. The increased strength of the slabs allows them to withstand quite significant loads, both in the longitudinal and transverse directions. Moisture resistance is good, but additional waterproofing is still recommended.

Among the advantages of glass magnesite it should be noted:

  • good thermal insulation properties;
  • versatility of use;
  • fire-resistant properties and non-flammability;
  • relatively small thickness;
  • the ability to bend sheets, making radius formwork;
  • high surface adhesion.

The main disadvantage is considered to be the complexity of installation work due to the need to process the material. When cutting it, jigsaw files and wheels wear out 3-5 times faster. It will take more time for installation.

A metal sheet

Permanent metal formwork is used when there is a need to strengthen the foundation structure and obtain a perfectly flat surface of any, even the most complex, configuration. Mainly used in industrial construction. Private developers practically do not use this technology.


The formwork structure is assembled from steel or aluminum sheets mounted on a metal frame. The formwork elements are connected to each other using special locks, anchors or overlays.

The number of connections is calculated in such a way that when pouring the concrete mixture, possible deflection of the sheet is completely eliminated. As a result, metal formwork provides the most accurate foundation geometry. Maximum deviations from dimensions do not exceed 2 mm.

To protect steel sheets from corrosion, their surface is coated with powder paint or a thin layer of zinc. If welding is used, the damaged protective layer is cleaned and repainted.

Among the disadvantages of using metals for installing permanent formwork, one should note the high cost, significant weight and the need for additional thermal insulation.

Strip foundation with permanent formwork using the example of polystyrene foam boards

Work on the construction of the foundation structure begins with marking and digging trenches to the designed depth. The width of the trench should be 0.5 meters greater than the width of the foundation on each side of it. After completing the excavation work, it is necessary to fill it with a thickness of 20-25 cm and compact it well. To provide the bottom layer of waterproofing, 2 layers of roofing material or waterproofing are spread at the bottom of the trench.


The most difficult part of installation is installing the first row of slabs. Therefore, to temporarily fix them, stick scraps of reinforcement or steel rod into the ground. Then you can simply push the slab onto the protruding rod and it will stand upright.

Opposing walls can be connected to each other using special clamps, standard coupling bolts installed in polypropylene tubes, or ordinary wire along the internal wooden spacers. During assembly, it is necessary to strictly adhere to the design geometry of the foundation.


Installation of the second and subsequent rows.

To ensure that the integrity of the formwork is maintained, the concrete mixture should be poured in layers.


Initially, lay a layer of no more than 0.5 meters, and after the initial setting of the concrete, add the rest.

If the slabs do not have a factory protective coating, it is recommended to treat the outer surface after pouring and hardening of concrete

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