The construction of a country house or foundation by cast casting requires considerable effort, but in this way you can get a finished building in a short time. In order for the structure to be solid and have the necessary configuration, you need to choose the right formwork material in accordance with climatic conditions and the upcoming workload.
What is formwork
Formwork is a set of parts for creating a mold into which concrete is further poured during the construction of buildings. It can be of various types, and the use of one or another option depends on the constructive structure, the materials used and construction technologies. Climatic features in the construction region play an important role when choosing formwork.
High-quality wooden formwork is very popular among individual developers
The defining moment for the device of the support base for any structure is the formation of formwork. The best material for formwork is a metal sheet. It is easy to install, allows you to get a flat concrete surface and can withstand repeated use, especially in the construction of typical buildings. But at a cost it is available only to large construction organizations. For a private developer, such material is expensive. In suburban construction, preference is given to traditional types of formwork - wooden or plywood structures.
Formwork can be removable or non-removable. In the second case, it performs additional functions of insulation or waterproofing.
The use of fixed formwork made of polystyrene foam allows you to do without further warming and waterproofing the foundation
Strict requirements are imposed on any foundation formwork:
- sufficient strength to withstand high pressure on the walls from the concrete mortar;
- strict observance of the dimensions of the structure;
- the absence of gaps between the formwork shields larger than two millimeters in order to prevent leakage of the solution;
- the possibility of reuse (for removable modifications).
When designing buildings, among other requirements, the formwork for all of its elements made of concrete is separately specified.
The most popular are panel and small-panel products.
Frames of this design are made of wood, metal or plastic. Small-panel formwork is considered to be a prefabricated square or rectangular shield up to three meters in size and weighing up to 50 kilograms. These requirements are presented for reasons of the ability to move and mount such parts manually.
Small-panel formwork made of wood is traditionally used in suburban construction
The formwork package includes the following parts:
- The shields themselves are prefabricated. Their working surface must be very even in order to ensure high quality castings. Shields can be of different sizes, but they always consist of a deck (rows of boards directly holding a concrete mortar) and a frame.
- Fasteners - special latches, locks, jumpers and screw connections.
- Elements of support for the frame in the form of slopes, stakes and stops, which allow to fix the frame unchanged even under load from concrete mortar.
Small-panel formwork is usually removable. But recently, another constructive solution is gaining ground. The formwork is made of polystyrene foam blocks, which also perform the functions of heat and waterproofing. When hardening concrete, such surfaces do not require any additional finishing, except for sealing joints.
Small-panel formwork can be made of the following materials:
- Wood. The wooden frame is lightweight and easy to install, which makes it a popular foundation for the device in individual construction. The disadvantages of this design include high adhesion of concrete to wood, which makes it difficult to clean the surface of the adhering mortar. This disadvantage is overcome by laying a plastic film on the walls of the formwork before pouring.
- Steel or aluminum formwork. They have a large weight, which is why in most cases the use of hoisting-and-transport mechanisms during installation is required. The advantage of metal products is high strength, which can significantly accelerate installation work. Aluminum formwork is lighter than steel, but its strength properties are lower, therefore, it requires additional fastenings. Metal products are reusable, so in some cases the formwork is rented during the construction of the foundation.
Steel formwork is used at large facilities, because it can significantly accelerate construction and installation works
- Plastic formwork is usually non-removable. The most common option is polystyrene foam blocks. They have special grooves for connection with each other and low weight, so the installation of such a formwork is quite simple. The relative disadvantage is the high cost, but it is offset by an increase in productivity due to the lack of the need to disassemble the formwork, as well as insulation and waterproofing of the foundation at the end of its construction.
Large-panel formwork differs from small-panel formwork only in block sizes and is most often used in industrial construction.
Photo gallery: large-panel formwork of various types
- Large-panel aluminum formwork ensures high quality wall casting
- Such a frame allows you to assemble formwork of any shape
- Large-panel formwork is usually used in the construction of large buildings
Such a frame for a support base relates to prefabricated structures. When it comes to foundations, these are usually fixed frames in the form of articulated blocks. They can be made of concrete, wood concrete, polystyrene foam and other similar materials. In shape, such elements are similar to cinder blocks, but with through openings. They are filled with concrete. The design of the blocks allows for layered reinforcement of the foundation. At the same time, the reinforcement bars are placed in recesses specially provided for this.
Since the blocks are not intended for dismantling, their front side can be made with trim elements.
In the block formwork there are special places for installing the reinforcing cage
The principle of operation of such a frame for concreting is that the formwork is constantly moving with a continuous supply of concrete mortar. It is made of metal. The metal case is moved by electric or hydraulic jacks. In addition to formwork panels, the equipment includes:
- supporting beams and jack frames;
- hanging scaffolding for staff;
- internal scaffolds for concrete workers and fitters and the placement of the pumping station.
Sliding formwork has a platform for accommodating people and equipment
This technology of construction of buildings has several advantages and disadvantages. The first include the following points:
- High speed of construction of objects: with three-shift continuous work during the day, one floor is erected.
- Cheaper construction by up to 20% compared with the installation of plates.
- The ability to customize snap-fit solutions for structural and architectural solutions.
Together with the positive aspects of the process, there are a number of disadvantages, such as:
- The complexity of the formation of reinforcing elements.
- Inability to perform large format openings.
- The increased complexity of the manufacture of floors.
- The high cost of work in frosty weather.
- The need to use a solution of high quality.
- Dependence on the continuous flow of concrete.
A number of disadvantages are eliminated by the use of special technological methods. So, to ensure the continuity of pouring and eliminate the risk of interruptions in the supply of concrete during its preparation, special additives are used that increase the curing time of the mortar to 18 hours.
One of the important points of concreting in this way is the impossibility of using deep vibrators. When this tool touches the formwork body, previously filled layers are destroyed. To avoid this effect, concrete is used with the addition of superplasticizers, compacted under its own weight.
The technology of construction using the sliding formwork method is used in the construction of buildings with a height of at least 25 floors. Otherwise, it becomes unprofitable.
Concreting the tunnel arch using the sliding horizontal formwork method is efficient and economical
This design is used for the construction of ceilings at a height of 1.5 to 20 meters.
Volumetric formwork is a structure consisting of vertical posts and horizontal jumpers called crossbars. Jacks are installed on the lower starting racks, which regulate the height of the structure and the horizontal position of the ceiling. In the upper part, special grips (univilki) are installed on each rack, in which supporting elements are placed in the form of wooden or steel beams.
The basis for the installation of the formwork table is a specially prepared flat platform on which shoes and jacks are installed.
Volumetric formwork is used in the construction of various industrial or cultural facilities, as well as bridges and overpasses.
The use of bulk formwork allows you to build reliable floors from any material at high altitude
Removable and quick-detachable formwork
Types of designs of removable formwork can be different in their purpose:
- for the installation of foundations;
- for casting walls;
- for the construction of concrete floors;
- for the manufacture of columns.
The main differences of formwork is their separation according to the materials used. But regardless of this, they all consist of several basic elements:
- deck products (boards);
- girdle frame device for assembling panels in a box structure;
- braces and stops (struts) to give the frame strength and stability.
In industrial construction, quick-release formwork made of sheet metal with stiffening ribs is often used. Such products are manufactured at specialized enterprises, so the parts are characterized by a high degree of compatibility among themselves, the accuracy of the fit and the ability to withstand many cycles of use - from 100 to 1000. Therefore, in the construction routine they are often called inventory.
Metal quick formwork can be applied up to 1000 times
Such formwork is used only on large construction sites, since their cost is too high for a single use in the construction of a country house. However, it is possible to rent finished formwork for rent.
Formwork materials may be different, but they should have a fairly flat surface. It can be chipboard, sheet slate, plywood or profiled sheet. The main requirement is the ability to tightly connect the formwork elements to each other.
Formwork made of waterproof plywood allows you to get a high quality wall surface
The most common formwork material to this day is wood. Use a planed board with a thickness of 10 millimeters, without making any special quality requirements. If it is used as an inventory product, the maximum number of cycles of use is 30, although neat builders use ready-made shields for years, replacing them as they are retired.
Sheet metal as formwork is not often used due to the high cost. But this material is the best and perhaps the only one with which you can create the foundations of complex curvilinear configurations.
In the metal formwork, you can cast a durable structure of any necessary shape
The easiest and fastest way to build a foundation is the use of expanded polystyrene boards.
Building a house using fixed frame elements is similar to playing with the Lego constructor. The foundation and walls, up to the internal partitions, are mounted from blocks or sheets of expanded polystyrene, wood concrete or concrete blocks and poured with concrete. The advantage is the quick construction of the building and its good performance.
Polystyrene blocks are very precisely interconnected, and during the operation of the facility they act as a heater
Formwork is a temporary auxiliary structure that determines compliance with the size, shape and position in space of structural elements of a building under construction.
The main parts of the formwork are:
- boards to give the object a design form, to ensure surface quality, size and proper location;
- a fastener system that ensures the correct and unchanged arrangement of the formwork elements relative to each other;
- supporting and supporting parts to prevent formwork deformation during concrete pouring.
Different ways to create a wooden formwork for pouring a quality foundation
The forming frame must ensure the achievement of the following results:
- Be strong enough to withstand the mass of concrete poured into its cavity.
- Stability, not shifting under the influence of loads.
- Have a clean and even forming surface to obtain high-quality planes on the finished object.
- To be sealed to such an extent that the solution does not leak during pouring.
- Provide design mobility for quick installation, convenient transfer to another facility and operational assembly.
- Allow multiple use of formwork at different sites.
The main materials for the manufacture of formwork are wood and its derivatives. In recent decades, various plastics and composite materials have become increasingly popular.
In the construction of buildings in an industrial way, formwork made of sheet metal is widely used. Their main advantages are determined by the following factors:
- High turnover associated with ease of assembly, installation and disassembly.
- Good surface quality of cast objects.
- The ability to manufacture parts and shapes of complex configuration.
- Durability and reusability.
Design features of formwork
Collapsible-moving cases are assembled from separate shield elements fastened with screeds, belts or ribs using screw fasteners.
Formwork elements are pulled together by screw pins and bolts
The technology for the use of formwork consists of quick installation, pouring concrete and quick disassembly, followed by rearrangement to another place (hence the name "collapsible - permutable").
The main elements of small-panel formwork are L-shaped or straight boards, equipped with mounting and supporting devices. Compared to large-shield ones, they have a weight of not more than 50 kilograms for manual movement.
The rules for the manufacture and operation of formwork devices are regulated by a number of documents, including:
- GOST 52086–2003 - “Formwork. Terms and Definitions".
- GOST 52086–2003 - “General technical requirements for formwork”.
- GOST 23478–79 - “Formwork for the construction of concrete and reinforced concrete structures. Classification and general technical requirements. ”
- SNiP 3.03.01–87 - “Bearing and enclosing structures”.
A complete list of regulatory documents is difficult. GOSTs and SNiPs are designed for all types and types of formwork, they are the main document for the designers of such objects. Based on them, technological processes are developed that are mandatory for execution in production.
Video: the manufacture of wooden formwork
Of course, you cannot teach all the knowledge of construction. But you can help learn the basic tenets that will be very useful in choosing materials and methods for their rational use. We hope that our article will help to produce high-quality formwork for your home.