The choice of material depends largely on the type of construction, since it is necessary to calculate the strength of boards, shields, metal and other elements that participate in this "interactive event". Suppose that a one-story house or garage is being built. For formwork, we need OSB sheets with a thickness of 12 mm, 10 mm can be used, but it will be necessary to pour concrete gradually so that the “belly” does not squeeze out anywhere. Instead of OSB sheets, you can use old wooden doors, metal gates, iron sheets and everything that is not weaker in strength and has a flat surface.
It doesn't have to be exactly on both sides. Even on the inside, irregularities of 2-3 centimeters are allowed - this is quite normal and will not affect the process in any way. The main thing is that you can easily pick this material from the concrete later, that is, without any elements that fall into the space intended for pouring concrete. Next, we need a wooden beam 50x50 mm, which we will cut. It is desirable that it be made of hardwood, the ideal option is larch. Its cost, of course, is considerable, therefore, if there are not enough funds, you can buy 10 meters of pine timber.
We expose the formwork and the internal screed
In order for the formwork for the foundation to be even, it is necessary to level the sole according to the level, make sure that its angle of inclination is insignificant, and there is a small gap between the OSB sheets and the ground, which can easily be filled with mortar. Next, you need to follow the instructions.
Step 1.
We cut a wooden beam 25 centimeters each (depending on the width of the foundation, if it is 30 cm, then we cut it into 30), and we make sure that the cut is as even as possible. We will need about 4 such pieces per 1 meter of the running foundation, if its height is 150 centimeters (average for a house).
Step 2.
We put 2 sheets of OSB or shields opposite each other, insert a bar 25 centimeters long between them and screw 1 screw from different sides through the OSB plate. Such a procedure is also necessary when installing ordinary boards as formwork, as it significantly increases the strength of the entire structure.
Step 3.
We fasten the next block of OSB or any other material so that there is a minimum gap between them, we screw it with slats. So we expose everything to the very end, so that there are no gaps anywhere. The thickness of the foundation will be the same everywhere, as you can control it with a wooden block. Such a strip foundation formwork device can significantly increase its accuracy.
Now we have a finished structure that needs to be leveled left and right. It still moves easily and can be corrected, but it is better to initially set everything in order to avoid possible “waves”. It is much harder to work with boards, although it will turn out 20% cheaper. The thickness of the board for the foundation formwork does not have to be large - 1.5 cm will be enough, because the main thing is internal reinforcement and external supports.
Outer spacers
Now let's move on to the most important part of our business - external formwork supports. Without them, it will simply fall apart, so you need to take a little time and allocate materials for the construction of such elements. Consider step by step instructions on how to do this.
Step 1.
We cut a wooden beam measuring 60, 90 and 120 centimeters. We leave 1 edge cut at an even angle, and make the other 45 degrees.
Step 2.
Every meter we install 3 supports at a height of 60, 90 and 120 centimeters, respectively. We rest against the ground with a right angle and hammer the beam a little, after which we tilt the pointed end to the OSB sheet, to which it fits perfectly. We screw the screw.
Step 3.
We hammer in the vertical supports. Basically, the entire structure will rest on them. You need to take a stepladder and metal pipes, corners, squares - everything that has a good bearing capacity and hammer them 50-60 centimeters into the ground, and right next to the formwork. This will not allow the bottom to move away.
Making formwork for a strip foundation in this way will make it possible to protect the structure from breakage as much as possible, even when the foundation is quickly poured. But do not rush, it is better to do everything in several stages - the effect will be much better.
At any construction site, a foundation formwork is a necessary element. During the pouring of concrete elements of the building, for example, armored belts, stairs, supporting columns and ceilings, formwork is also indispensable. Formwork is a type of structure, the task of which is to give a certain shape to the concrete mixture. It is usually made of wooden boards, plates of various materials or metal. One option is OSB formwork. The advantage of these boards is that they install much faster than boards.
Oriented Strand Board
OSB/OSB board is easily recognizable by its characteristic wood structure. Oriented strand board (OSB) is a type of engineered lumber similar to chipboard that is formed by adding adhesives and then pressing layers of wood chips oriented in a particular way. The surface of OSB is rough and motley, with individual chips (chips) about 2.5 cm * 15 cm, located unevenly to each other and having a different appearance and thickness.
Usage
OSB boards are widely used in housing construction. The mechanical properties of this building material allow it to be used for a variety of purposes. Most often used as a crate on walls, floors, roof decking and formwork for foundations and other concrete (reinforced concrete) building elements. For exterior walls, the panels are pre-laminated on one side; this simplifies installation and increases the energy efficiency of the building envelope. OSB is also used in furniture manufacturing.
Production
The slab is made in the form of wide mats, from layers of differently oriented chips, compressed and glued together with wax and synthetic resin adhesives (95% wood, 5% wax and resin). Commonly used types of resins include phenol formaldehyde, melamine molded urea formaldehyde or isocyanate. All of these binders are resistant to moisture. A combination of binders is often used, typically isocyanate in the core and urea formaldehyde in the top coats. This has the advantage of shortening pressing cycles while imparting a bright appearance to the panel surface.
The layers are created by cutting the wood into strips, which are sifted and then oriented with various devices when fed to the molding line. For the outer layers, the chips are aligned along the strength axis of the panel, while the inner layers are perpendicular. The number of layers to be placed depends partly on the thickness of the panel to be obtained, but is limited by the equipment installed at the plant. The individual layers can also vary in thickness to give different thicknesses to the finished panel (usually a 15 cm layer results in a 15 mm thick panel). The mat is placed in a thermal press to compress the raw material and bond it through heat activation and curing of the resin that coats the wood. The individual panels are then cut from the mats to the desired dimensions.
Wooden OSB panels can be cut and installed with the same ease and the same tools as real wood.
Properties and types
Adjustments in the manufacturing process can introduce differences in thickness, panel size, strength and stiffness. OSB boards are void-free and water-resistant, although they require additional skins to achieve water-tightness and are not recommended for outdoor use. The finished product has properties similar to plywood, but is more uniform and cheaper. In a fracture test, OSB has a greater load capacity than milled wood panels.
Four types of OSB are defined in terms of their mechanical characteristics and relative resistance to moisture:
- OSB/1 - general purpose boards for interior decoration (including furniture) for use in dry conditions;
- OSB/2 - load-bearing boards for use in dry conditions;
- OSB/3 - load-bearing boards for use in wet conditions;
- OSB/4 - load-bearing boards (for significant loads) for use in wet conditions.
Although OSB does not have a continuous fiber like natural wood, it does have an axis along which the drag force is greatest.
It is the strength of the OSB boards that makes their use as a formwork material expedient, and the ease of processing makes it possible to do the work yourself.
Installation rules
Before starting work on the manufacture of formwork, it is necessary to prepare tools and additional materials for its connection, strengthening and installation. Tool kit - standard for carpentry:
- axes (large and small);
- hacksaw (electric saw or jigsaw);
- a hammer;
- screwdriver (screwdriver);
- measuring instruments (tape measure, level, plumb line);
- wooden beam, pieces of reinforcement and plastic pipes of small diameter;
- fastening hardware (long bolts or studs, nuts, self-tapping screws).
OSB boards are easy to cut into pieces of the desired size using a table saw or a hand-held electric saw. A hacksaw will also successfully cope with this. The slabs can also be cut at a special stand in a building materials store, according to previously taken dimensions.
In order to avoid deformation of individual parts of the formwork, when pouring, they should be reinforced with stiffening ribs from wooden blocks. They should be screwed around the perimeter of each part and across it. This precaution is especially relevant if large area sheets are used, such as when making formwork for floors or high foundation walls.
In the manufacture of formwork on both sides of a concrete building element, two opposing parts are put together, then holes are drilled in them, at the top and bottom, for a mounting stud / bolt. Having installed a piece of plastic pipe of the required length between the OSB sheets, a pin is passed through it and clamped with nuts, forming a box.
To prevent the plate from tearing from the weight of concrete, it is advisable to place washers of large diameter under the nuts.
When making corner boxes for the foundation, one of the walls of the two boxes is made longer so that a corner can be formed.
From the prepared boxes, it is quite simple to form the foundation of the desired configuration. The finished boxes are lowered into the pit / trench, arranged in accordance with the building plan and fastened together with bars. The formwork of the foundation itself is fixed with reinforcing pegs hammered into the ground. For a high foundation, in addition to reinforcement, it is desirable to use struts, approximately every 70 cm, this will prevent the destruction of the structure, which is possible when pouring concrete. The gaps between the individual boxes can be closed with glassine or polyethylene.
When fixing the plates, you should not connect them end-to-end. Slots with a width of 2 - 3 mm are required to compensate for minor material movements caused by external influences (temperature, humidity).
If OSB boards are used to make an armored belt or a low foundation, you can get by with a simpler method of mounting the formwork. The details of the armored belt are attached to the wall with the bottom part using long self-tapping screws, and on top with wooden bars. Then, with the help of a knitting wire, the parts are additionally pulled together. A low foundation is reinforced with self-tapping screws on stakes made of wooden bars, which are driven into the ground, in accordance with the plan of the house. Then the formwork is reinforced with struts from the outside.
In the manufacture of formwork for overlapping, OSB boards are laid on a frequent (50 * 50 cm) lattice of supporting beams, which is installed on racks of a given height. It is advisable to install racks every one and a half meters. For their manufacture, you can use metal pipes or, if it is possible to rent them, use industrial racks for monolithic work.
It is advisable to pour concrete around the entire perimeter, without creating excessive stress in one place. If it is impossible, for various reasons (technological, organizational), to carry out pouring without interruptions, then work joints should be created in accordance with the rules for concrete work. So, for example, the working joint should be perpendicular to the axis of the concrete element, without any bevels.
In this video you can see how to make an armored belt formwork from OSB:
OSB boards can be used repeatedly (up to 10 times), and after dismantling the formwork, they can be used to make rigid sheathing on the roof or floor in the attic. That is, if you properly organize the order of work and carefully use the material, then when using these plates, you can do without waste and, accordingly, save money.
Oriented Strand Board (OSB) is definitely the best material for concrete formwork. To attest to this confidence, one should refer to the GOST requirements for formwork for concrete structures.
It is not necessary to list them completely, but the main thing is that the formwork must be rigid and durable; chemically neutral; and most importantly - to provide waterproofing. The lack of proper waterproofing of the formwork inevitably leads to the loss of "cement milk", as a result of which the concrete will not acquire the required strength.
Properties
Does OSB formwork have such properties? It has been proven in practice that OSB structures have great strength and excellent moisture resistance. Formworks made of boards (planed and not planed), plywood or chipboard easily change shape under the influence of moisture and concrete pressure. It will not be possible to achieve a perfectly even design when using these materials. On the contrary, OSB formwork has a very solid strength factor and freely transfers the pressure of concrete. In addition, OSB is chemically neutral and cannot interfere with the maturation of concrete.
Moreover, the installation of formwork from boards, plywood, chipboard takes a lot of time and money, and during dismantling it is almost impossible to avoid damage to concrete and formwork material. In contrast, OSB formwork is quite freely assembled and easily dismantled, it can be used repeatedly, which makes it more profitable from a financial point of view - the cost of formwork materials is reduced and construction time is reduced.
Waterproofing
And now about the most important thing, about waterproofing. OSB formwork protects concrete from moisture loss during the curing process. Impeccable waterproofing is provided by the design features of the OSB formwork. The plates in this case act as support blocks, and the entire structure is lined with plastic wrap. This design guarantees the preservation of moisture in concrete, prevents the loss of cement laitance. Minimum cost while achieving maximum strength of the concrete structure.
Professionals have appreciated the features of OSB formwork and now not a single large-scale construction project can do without it. In addition, any zealous home craftsman has the opportunity to take advantage of OSB in the construction of strip foundations.
Formwork is an integral part of the construction site. It is used not only for the construction of a strip foundation, but also for stairs, armored belts, floor slabs, columns, wall structures. Allows you to create products from a concrete solution of a certain shape. Often the main elements for its manufacture are wooden boards or metal plates. One of the most practical options is OSB.
Oriented strand board is a type of engineered lumber that resembles chipboard in its wood structure. It is formed with the help of special adhesives and by pressing several layers of wood chips, oriented in the necessary way. It has a somewhat rough surface, where small chips of wood with dimensions of approximately 2.5x10 or 2.5x15 cm are visible. They are randomly located, while their thickness and appearance differ from each other.
To create OSB, three thin layers of chips are used, while the two extreme opposite to each other are laid along, and the middle one is perpendicular. It is this oriented arrangement that provides proper strength. Water-resistant synthetic resins and high temperature pressure molding are also applied to improve performance. Due to the homogeneous structure, they work well for bending and tearing.
OSB formwork has:
- Low hygroscopicity. The material is particularly resistant to swelling or delamination.
- Ease of processing. Easy to saw and drill.
- Reusable. OSB-3 do not lose their qualities, since one of the sides is laminated.
- Light weight. It simplifies installation work, therefore it is in demand among private developers.
- The possibility of using large-sized slabs, which allows you to create large-panel formwork with a small number of joints.
Advantages and disadvantages of such formwork
The manufacture of OSB is carried out by pressing large chips (50-80 cm) under high temperature. At the same time, waterproof resins and chemical additives are added that exclude damage by fungal microorganisms or mold. Under the influence of moisture, the products are not able to warp and collapse for a long time, due to which they are effectively used in the construction of formwork for the foundation.
Compared to wooden boards, the boards are not deformed due to the influence of external factors and atmospheric precipitation, therefore they are used several times without loss of performance. They have perfectly smooth edges, which is not always possible to achieve from ordinary wood.
Since OSB is easy to saw, you can create panels of any size, which makes it easy to select the right elements. The material is sufficiently elastic, therefore it is less prone to destruction under bending loads. Also, this and its low weight makes it possible to easily and quickly create formwork, saving time on construction.
OSB boards have some disadvantages:
- Poor resistance to high concentrated loads.
- They have phenol in adhesive compositions, which is harmful to human health.
- Panels 3 and 4 types can only be placed outside the building.
Plywood and OSB formwork is often used in the construction of buildings and structures for various purposes. Due to their mechanical properties, they are widely used for wall cladding, roof floors, foundation frames, floor slabs and other reinforced concrete monolithic structures. There are elements with a laminated surface, which greatly simplifies their installation and increases their effectiveness as enclosing products. The panels are also used in the manufacture of furniture products.
Necessary materials
Calculation of the formwork for the strip foundation is carried out only after the installation of trenches. In this case, the height of the basement of the building and the specific density of the concrete solution, which imposes a certain load on the shields, should be taken into account. For its manufacture are used:
- Wooden blocks as stiffeners.
- Hardware for connecting the structure (bolts with nuts, washers, studs).
- Metal corners for reliable fastening of plates.
- Plastic pipe for fastening opposite shields.
- Reinforcing rods.
- Plywood or slats to cover gaps.
- Self-tapping screws for connecting OSB and glassine.
At the preparatory stage, cutting of plates of the required dimensions, plastic pipes and fittings is carried out, and the dimensions of the shields are also calculated.
Step-by-step installation technology
The assembly of the fence begins after excavation and laying a sand cushion under the strip foundation. The most practical option is a removable formwork device. Prefabricated panel systems allow you to quickly and easily assemble panels of the desired size with correction of corner sections.
Provide places for laying engineering and plumbing communications that will be located on the construction site.
Installation is carried out in the following sequence:
1. OSB-plates are cut according to the dimensions of the edges of the foundation, while the height is made slightly larger than the net level by 15 cm.
2. Frames for walls are made. The budget option is wooden, however, for repeated use, you will need shields made of metal bent-welded profiles.
3. The OSB blank is attached to the frame with self-tapping screws, the caps of which should be on the inside and slightly recessed.
4. Each side of the formwork is reinforced with transverse bars in increments of 40 cm. This will allow you to observe the geometry of the structure being created.
5. Opposite elements are connected with metal studs, which are threaded through previously drilled holes with a diameter of 16 mm. Fasteners should extend 3-4 cm beyond the shields on each side to ensure secure fastening with washers and nuts. The lateral plane of the fasteners is chosen wide so that under the pressure of the mixture they do not push through the OSB.
6. Plastic pipes are threaded, which will allow you to maintain the accuracy of the width on any segment of the strip foundation. After pouring the mortar and its hardening, they remain in the concrete body, while working well as ventilation.
7. If there are no pipes, fastening can be done with nuts. Then there are about 4 pieces with washers per side. When dismantled, they are removed and the ends of the studs are cut off flush.
8. When pouring the concrete mixture, the corner sections perceive the greatest efforts, therefore, reinforcement is carried out with wooden blocks vertically driven into the ground. For additional reinforcement, steel corners are used to connect the shields to the pegs.
To give maximum rigidity, holes are made in the shields into which embedded reinforcement products are inserted in the shape of the letter "T". The long side is welded to the reinforcing cage of the foundation and the mortar is poured. After solidification, the excess parts are cut off with a grinder.
Inclined bars on the outer side of the structure with a step of 1 m allow you to keep it in a vertical position until the very end of construction. Spacers should be attached to the shields at an angle of 30-45 °, then the possibility of their collapse is excluded. At the end of the formwork device, a control check of the parallelism of the side faces is carried out. This will require a piece of timber and a water level.
Concrete work can be carried out in layers, taking small breaks between pouring. Then the solution will set, and the spacer pressure will decrease. However, if the foundation area is small, it is recommended to lay the mixture in full, excluding the appearance of cold joints.
Formwork reduces construction time by combining the laying of the foundation and its insulation. To do this, at the stage of the installation of enclosing structures, polystyrene plates are laid between the reinforcing cage and the shields.
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When constructing suburban real estate, developers apply strip foundation formwork from boards, plywood, OSB. The quality and design of non-removable polystyrene foam blocks do not meet the requirements of the SP standards for concrete work.
Construction and materials
used by the owner of a suburban area once. Therefore, the most important condition for reducing the construction budget is the reuse of structural material in the following stages. Shields are knocked together from edged boards, OSB, plywood, dismantled after stripping, turn into partitions, draft floors, roof lathing, ceilings. 
To save lumber, wood-containing slabs from contact with the concrete mixture, the boards are wrapped from the inside with polymer films. With these waterproofing materials, it will later be possible to make a horizontal layer that cuts off the walls from the foundation. When laying a mixture from a concrete mixer, the formwork experiences loads per unit surface within 400 kg. If the concrete is poured out of the mixer, the load rises to 600 kg, the concrete pumping requires special strength of the decks, since the loads reach 800 kg.
Wheelbarrows are transported along the shields, builders walk, so the minimum thickness of a deck made of different materials is 2.5 - 5 cm. The thinner the lumber, the more difficult it is to find a use for it in the future, more often you need to put racks with jibs. Depending on the height of the belt, horizontal loads increase significantly. Therefore, the following schemes are recommended:
For a non-buried belt belt, 2.5 cm boards can be used. The step of the racks will be 60 - 80 cm for a tape 50 cm or 20 cm high, respectively.
Monolithic tape technology implies the presence of an underlying layer instead of heaving soil, 5 - 7 cm footing on top of it with 2 layers of welded waterproofing material. Therefore, problems with the installation of shields do not arise in principle. To fix the decks in space, stakes, jib bars, ties, horizontal stops are needed.
Attention: To reduce labor costs at the stage of protecting concrete structures from moisture, freezing, insulation can be placed in the formwork, a penetrating composition is added to the concrete. After that, the foundation becomes waterproof with an outer contour of insulation, which does not need to be glued, fixed with dowels.
Manufacturing technology
It is better to build formwork panels on a flat area directly on the site. Subject to the construction technology of the strip foundation, it is possible to unify the dimensions of the formwork, apply the in-line method:
The simplest option is the MZLF tape on a flat area. To calculate the number of boards, you must perform the following steps:
- add the length of the outer sides of the foundation
- divide the amount by 6 m (standard lumber length) to get the number of boards in one belt (N 1)
- add 5 cm to the height of the tape (shields are mounted above the design level so that the concrete does not splash out during vibration compaction)
- divide the result by 10 cm or 15 cm (the width of one standard board) to get the number of belts (N 2)
- multiply N 1 and N 2 to get the total consumption of lumber
Attention: The cube contains 44 boards 2.5 x 15 cm, 37 boards 3 cm thick or 27 pieces 4 cm thick. Taking into account the mounting step of the boards on the footing, you can calculate the board / beam consumption for racks, jibs, stops.
If sheet materials are used, it is extremely important to reduce the amount of waste, scraps. The length of the decks should not exceed 3 m, so that it can be moved, mounted in windy weather by two workers.
Board shields
After purchasing the material for the manufacture of shields, the following technology is used:
Then, a polymer film is shot on the inner surface of the shield deck with a stapler. This will prevent the seepage of cement milk through the cracks, save lumber for recycling, and facilitate stripping.
Attention: In the presence of a screwdriver, assembly productivity is increased by fastening lumber with self-tapping screws. However, with serious loads on the formwork panels, it is better to use nails. Hardened screws can be sheared by concrete pressure.
plywood deck
Shields made of sheet materials are constructed using a different technology:
The inner surface is processed with a film, the decks are laid out with components in the building spot. Diagonal lintels in frames significantly increase the reliability of the structure.
Shields from OSB boards
Experts do not recommend the use of oriented strand board, since this material is inferior to plywood in terms of rigidity with the same thickness. Wetting during precipitation leads to partial delamination, loss of appearance. 
However, this option is preferable if OSB is planned to be applied later in a continuous roof sheathing. Decks are built according to the above technology using a frame system. It is allowed to use OSB-4, in extreme cases OSB-3. The decks are pulled together with studs, lintels made of timber are strictly prohibited.
Curved formwork
Classic facades of cottages often do not suit individual developers. Semicircular bay windows, curvilinear walls are used, which require a foundation of a similar configuration. You can assemble such decks according to the following methods:
For a radius, curvilinear wall, it can be bent along a fiberboard contour drawn on the footing (with the front side inward), supported from the outside with board racks located close to each other. So that the fiberboard does not collapse when wet, its surface is sheathed with polyethylene.
Attention: All existing polystyrene fixed formwork is designed for walls. It is forbidden to compact the concrete inside it with a vibrator, the laying of reinforcing cages is impossible in principle (lintels interfere). The binding of frames inside the formwork, the destruction of polystyrene foam under the pressure of concrete, sharply reduce the productivity of the process.
Mounting Features
The unfolded decks begin to mount from any angle in the following way:
There is an option for fixing the decks with U-shaped clamps, which are put on the shields from above. Clamps are made according to the scheme:
This design allows you to fix the outer size of the tape, it is used only in conjunction with internal stops.
Attention: Shields for deep-laid tape are mounted after installation of reinforcing cages. Due to the large height of the decks, it is not possible to lay the frames inside the assembled formwork in compliance with the protective layers of concrete.
The tapes require holes for the entry of engineering systems, ventilation products. They are made by installing pipes passing through two shields. These void formers are also mounted after the reinforcement cages have been placed. 
External insulation of the strip foundation is often carried out during the construction of the formwork. This option reduces labor costs, but is only recommended when penetrating compounds are added to the concrete. Otherwise, it is impossible to waterproof the outer surface of the concrete structure; expanded polystyrene is not a full-fledged waterproofing layer.
For insulation of foundations, it is better to use expanded polystyrene grades XPS or high-density EPS. Thermal insulation is carried out according to the scheme:
In this case, the processing of the shields with a film can be omitted, after the concrete has hardened, the dowels will remain embedded in the foundation, the heat-insulating material will be held by their caps. When using a warm circuit, increase the distance between the shields by the thickness of the expanded polystyrene. The outer protective layer of concrete is measured from the heat-insulating material.
Thus, the construction of the strip foundation formwork from boards, sheet materials is not difficult. It is better not to use fixed formwork for foundations. The choice of material depends on the design of the roof, partitions, subfloors, in which they are usually used after stripping.