One of the first stages of the construction of structures for various purposes is the installation of formwork. Often this process is left without due attention. But already at the stage of preparation for pouring, it becomes clear that not everything is as simple as it was thought at first. Assembling the formwork will help assemble the formwork.
Types of formwork
There are three types of design:
- Removable, which is removed after the solution has completely dried. Such formwork is assembled from individual parts. The result is a collapsible structure that is dismantled and can be reused. Among the advantages of this type of formwork, ease of installation and the possibility of reuse are highlighted, which significantly reduces the financial cost of construction.
- Non-removable, respectively, one that is not dismantled. Installation of formwork of this type is carried out mainly from polystyrene foam or polystyrene. It remains part of the construction. And at the same time performs the role of insulation.
- “Floating” formwork is characteristic for the construction of a monolithic foundation, which is immersed in the ground. It is a shield assembled from boards, which is slightly higher in height than the planned concrete structure. The shield falls into the pit and is attached to its walls. Cardboard or roofing material rolls over it.
Several types are also distinguished, depending on the purpose:
- Wall formwork. Installation is carried out for the erection of vertical structures and walls.
- Horizontal, which is used for installation of the foundation and floors.
- Curved, which allows you to fill in details of unusual shapes.
The installation and dismantling of each formwork has its own characteristics. They must be known for the quality of work.
The advantages of fixed formwork
Installation of fixed formwork involves the purchase of a ready-made kit for work. It remains only to assemble the structure and make its installation. This implies a number of advantages that formwork of this type has:
- low weight of the structure;
- resistance to the appearance of fungus and mold;
Also, fixed formwork is at the same time a layer of insulation and is a foam block that is easily connected to each other. In this case, the inner wall is thinner than the outer. Thanks to this, a high level of thermal insulation is achieved.
The construction of fixed formwork
Installation of wall formwork using fixed blocks is much easier than the traditional method.
Work begins with the preparation of the site, laying a layer of waterproofing. Blocks are simply put on the foundation according to the principle of brickwork (with offset joints). This allows you to increase the strength (rigidity) of the structure.
To begin with, only one row of blocks is laid, then reinforcement (lap). There are special grooves for this. The fittings are interconnected by a vertical wire. The following rows are laid out in the same way.
The blocks are attached to each other by simply connecting special grooves by light pressure. They begin to pour concrete mortar on the third row of blocks.
In the process, there is one little secret. Walls will be more reliable if the joints of the solution layers remain in the middle of the block. To do this, fill the top row to half.
Features of the implementation of removable formwork
The main moments of the installation of formwork will be considered using an example of a removable collapsible structure. This type is most often performed by site owners without the help of professional builders.
The installation of formwork is made from boards, bars, plywood and other sheets of wood. The main thing is that these plates are smooth. All work begins with the preparation of the site. The site must be completely cleaned of foreign objects, debris, and so on. Then, using the bars, the angles of the structure being erected are noted. They will be the basis from which the remaining measurements will be performed. In accordance with the dimensions between the bars, the formwork shield is assembled .
Ready-made panels are attached to the corner bars using screws or nails. The mount must be secure. With the expansion of concrete, the pressure on the shield will increase, which can lead to cracking of the boards. The main thing is that the bar itself remains on the outside. In parallel to the assembled structure, another row is assembled at a distance of the future wall. The result should be a frame around the perimeter.
A layer of crushed stone or sand is poured into the finished formwork box. This will protect the solution from moisture loss, which will go into the ground. The technology of mounting the formwork provides for the protection of the wooden board from the flow of mortar through the existing holes. To do this, the shields are covered with a film or roofing material, which are fastened with screws or staples using a stapler.
All work must be carried out taking into account the level. It is very important. At each stage, the evenness of the structure is checked for height, length and vertical (especially important). Two rows of shields should go strictly parallel to each other.
Basic elements of formwork
Removable formwork, which is assembled independently, consists of the following elements:
- The deck, which is a flat shield, which is a fence of all shapes. The design must be strong enough to withstand the pressure of the solution. Therefore, it is made of plywood or edged boards with a thickness of 4-5 cm.
- Forests that are the support of the structure. They hold the walls, not allowing the solution to squeeze the deck. Forests are made from pine blocks or boards (2.5-5 cm).
- Fasteners are all the details with which all structural elements are twisted: wire, clamps, ties, hardware and so on.
The deck is most often assembled from boards with a width of 15 cm, which are connected in several rows using nails (driven from the inside, bent from the outside) or self-tapping screws (they are twisted from the inside). The distance between the boards should not exceed 3 mm. Shields fasten together with additional slats.
A simpler option for the manufacture of the deck is the use of moisture-proof plywood with a thickness of 1.8-2.1 cm.
Formwork installation
The frame will be installed evenly and in level, if the site is properly prepared in advance. It is marked with cords stretched between the pegs. The sand cushion is filled and compacted. If necessary, a foundation pit is prepared.
The formwork is installed in the following sequence:
- The perimeter should be marked with vertical guides (wooden bars, metal corners or pipes).
- On the rails, it is required to place the finished panels, maintaining the necessary distance between them (it is equal to the necessary thickness of the foundation).
- Firmly fix the deck. Support it from the outside with inclined bars (1 strut for each meter of the deck).
- Connect the shields together with 5x5 cm bars.
- Cover the inside of the formwork with a film (roofing material).
Foundations up to 20 cm high do not require serious construction. For them, bars are enough driven into the ground.
Installation of wall formwork
More complex is the process of erecting wall formwork. At the same time, small-panel and large-panel formwork are distinguished.
The first option is suitable for the construction of small buildings (country houses, utility buildings) and partitions between rooms. At the same time, small plywood shields are used.
The installation of large-panel formwork is typical for the construction of buildings with high heights. For work, use sheets of metal or large sheets of plywood.
For the installation of walls, a foundation is prepared in which reinforcement is stuck. Around it, a double-row formwork frame is assembled. When using ordinary plywood, the joints are coated with glue or sealant. There is currently a special formwork plywood on the market. Separate sheets of it are connected according to the principle of "spike-groove", which does not require additional sealing.
Types of floors
The installation of the slab formwork depends on the type of slab itself. The following types of structures are distinguished:
- On voluminous bowls. It is applied to designs with big height. In this case, vertical racks, jacks, inserts, crossbars and other elements are used to connect the individual parts.
- On blade scaffolds that are used for multi-story buildings. Instead of plywood panels, scaffolds are installed.
- In the scaffold type forests. This view provides for the installation of the frame. Racks are interconnected by a cup method.
- On telescopic bowls. Suitable in cases where the ceiling height is less than 4.6 m. It is based on tripods that support the entire structure. Shields of moisture-proof plywood are stacked on top.
Slab formwork
Currently, monolithic overlap is most often used. Using his example, we will analyze the process of mounting the formwork.
For formwork, vertical posts are used, interconnected by crossbars. They are mounted at right angles to the bars going in the transverse direction. A plywood shield, which is the bottom of the formwork, is laid on these transverse bars.
To carry out these works, the following materials are used:
- stand - timber with a cross section of 12-15 cm;
- crossbar and cross beam - edged board 16-18 cm wide and 5 cm thick;
- braces - 3 cm thick board;
- flooring - moisture resistant (laminated) plywood 1.8 cm thick.
Before starting work, it is necessary to carry out accurate calculations. It is important to determine the required number of racks, the step of their placement and other indicators.
Installation instructions for formwork floors
Instructions for the work include the following steps:
- To the upper part of the racks are attached longitudinal bars, the second end of which is fixed on the wall.
- The second row is collected in the same way. To do this, a 5 cm thick board is placed under the supports.
- The transverse bars are laid in increments of 60 cm.
- Install support stands (strictly vertical).
- Racks are interconnected by braces.
- Plywood sheets are laid on the transverse bars without leaving cracks.
- The ends of the floor are protected by masonry from blocks or bricks.
- Going to the frame of the reinforcement. In this case, if necessary, leave space for communications.
When all work has been completed, concrete can be poured. Formwork is removed after 3 weeks.
Conclusion
The installation of formwork of each type involves the use of certain materials. If boards are used, then they must be new. Rotten old boards can not withstand the load and break. Plywood must be moisture resistant or laminated.
All work must be performed in accordance with the calculations. This is especially important for the installation of formwork floors and walls.