How to properly make formwork on a strip foundation. Installation and leveling of formwork

Almost everything existing species strip foundations can be poured using only formwork - an auxiliary structure, which is often made from scrap material. It serves not only to ensure constant dimensions of the base, but also gives the foundation even correct forms and reduces the consumption of concrete solution. Plus, it can be removed, moved to another construction site and used more than once.

Types of structures

The construction of an auxiliary structure made of wood, metal or other materials involves the use of rigid structures interconnected and capable of supporting the mass of concrete, but some types also provide excellent thermal insulation characteristics Houses. For arranging formworks they are used different kinds materials, let’s stop and first look at the types of formwork for strip foundations:

Removable (collapsible). These are wooden, less often plastic and metal panels, which are assembled in the form of a constructor, ensuring reliable connection of elements and tightness of seams. In most cases, the calculation of the quantity necessary materials done on the spot when necessary. After use, you can remove and reapply. You can make it yourself from wood.
Fixed. This is a disposable design, made from polystyrene foam, and serves as the main thermal insulation layer. Needed when the building area is limited. Thanks to reinforcement with special supports and spacers, the foam plastic can withstand heavy loads, does not deform, and do-it-yourself assembly is done like a construction set from factory elements. It cannot be removed; it is necessary to calculate the panels for each specific construction. Various materials can be used, but most often polymer products.
Combined. Here wood is simultaneously used as outer layer formwork, and polystyrene foam as insulation. After pouring the foundation outer part The structures can be removed, while the insulation remains embedded in the concrete.

Several years ago, builders preferred to use removable formwork for strip foundations, since it is reusable and can be rented at affordable price. Moreover, many companies and small firms produce such formwork with their own hands and then rent it out at an affordable price. It is worth noting that it is difficult to erect the formwork correctly, according to all standards, taking into account the technical characteristics of the materials used, as well as the possibility of expanding the base if necessary.

Design elements and material

The formwork consists of several main elements:

Wooden boards rectangular or square shape arbitrary sizes.
Clamps for vertical placement of panels.
Horizontal internal bushings, they are used to ensure the required internal width of the tape and prevent the expansion of the panels
Waterproofing. It prevents liquid from leaking out of the formwork, and also ensures a faster drying speed of the solution.

Formwork for strip foundations can be made from wood. The most affordable and cheap material, the device is simple and anyone can make a frame with their own hands using available tools. For the production of formwork in private conditions, plywood up to 15 mm thick or edged boards 40 mm thick are used. In this case, it is easier not only to construct a strip foundation, but also to correctly calculate the required amount of materials.

Metal factory structures are strong and reliable. They are durable and reusable, but due to their large mass they are difficult to transport. Only experienced builders can install such shields correctly. Tape extension is not allowed.

Plastic formwork or polypropylene foam is lightweight, compact, expensive and versatile. Excellent for the construction of load-bearing walls and ceilings, as well as for pouring strip foundations. Plastic and polystyrene foam are artificial thermal insulation, calculations are made right on the spot, and the panels can be cut to your size. It is also easy to construct a plinth on such a ready-made, flat surface.

Installation of wooden formwork

To produce wooden formwork, it is better to use edged board or wide plywood. Ready-made shields of fixed sizes are made from these materials, then grooves are made on the external contours to connect the shields to each other. All joints are treated with waterproof sealant or polyurethane foam. The moisture content of the wood should not be high, the thickness of the cracks should be up to 2 mm. The height of the shields should not exceed 5-7 cm above the level of the foundation strip. Installing the formwork is quite simple, you can do it yourself:

First, the construction site is prepared.
The dimensions of the formwork are calculated, the appropriate materials are selected and the structures are assembled.
Then the shields are installed on the outside and reinforced with braces, where the main fixation will be the soil or reinforced pillars. The braces are nailed to the boards and installed at intervals of at least 1 m from one another, the minimum permissible distance is 30 cm for thick bases.
Jumpers of a fixed length are secured with nails or corners - this is the maximum allowable width of the foundation strip.
The inner part of the formwork is installed in the same way and tightened with clamps, nails or other fasteners.
The vertical and horizontal position of all shields is checked, the permissible slope angle is no more than 3 degrees, and they must not have deflections or bends. The condition of the surface of the boards should be regulated by slats, a level or a construction hydraulic level. Local deviations for plywood should not be 2 mm, and for boards - up to 3 mm.
After pouring the concrete solution, the formwork can be removed and reused, and the base can be constructed on a flat outer surface.

The correct positioning of the formwork panels can also be controlled using casting threads and wires, as well as fixed type fasteners. If not used removable formwork It is advisable to fix it on the inside of the polystyrene foam wooden planks, install strong hooks in them and connect the fittings flexibly. Then the hooks will tension both surfaces of the formwork and fix them within the specified parameters.

After installation, the inside of the formwork must be covered with roofing felt in several layers so that the concrete does not leak out, as well as to ensure waterproofing of the tape. Waterproofing must be laid from downward slopes, closer to the sand cushion, so as not to tear the layer during concreting. It is better to bend the upper part of the ball of roofing material over the upper edge of the formwork, secure it with clamps or screws, and secure it with a stapler. Then the sheet will withstand the load that will occur when pouring concrete from a concrete mixer.

How to install formwork for strip foundations on unstable soil

Even just digging a trench or pit in loose soil is fraught with some danger due to its possible shift. Therefore, first they make the external formwork of the trench in order to prevent soil shifts, and only then equip inner part trenches.

To protect the labor of workers, a trench is dug at a certain slope of the walls and of sufficient width for convenient installation of shields. Then the formwork is installed, which is often made in several layers, where the intermediate zone is the clamps of the outer edge from the ground and the inner edge from the concrete mortar zone.

To ensure that the formwork stands securely, you can pour a layer of concrete on top of the sand-gravel mixture medium density so that it fixes the shields from the inside. When the formwork is installed on concrete base, then it is better to use special threaded ties. They fix the slabs together, prevent them from spreading under the mass of concrete, and steel bushings are provided inside the formwork.

How to arrange a combined formwork for a strip foundation

Combined formwork pays off when you need to build high building and install thermal insulation on a limited area of the construction site. The design involves a combination of removable and permanent formwork, which you can do yourself, while its design remains quite simple. From the outside - these are ordinary removable plastic or wooden boards, and inside there is a layer of polystyrene foam.

This design carries the advantages and disadvantages of two types of formwork. Some developers spend money and time on thermal insulation, especially when it is necessary to build a foundation without calculations in a short time. The disadvantage of such formwork is that when it comes to waterproofing, it can only be placed on the outer surface, and the inner part of the insulation cannot be removed.

If the strip base is erected on strong soils that are not prone to heaving, then the trench is dug taking into account the thickness of the insulation, as well as the removable formwork panels. In the underground part, the insulation is attached to the walls of the trench, and in the above-ground part - using self-tapping screws. You can also use special mounting dowels and umbrellas, but then removing the insulation during restoration or repair is problematic. If the tape is installed in loose soils, then the insulation is installed completely immersed in the ground, provided that the level of frost heaving in the region is insignificant.

The role of permanent formwork for strip foundations

These are panels made of polystyrene foam, connected to each other by grooves in the shape of a construction set, so they are often made with their own hands according to ready-made drawings. A reinforcement frame is installed inside and then filled with concrete. Due to the presence of expanded polystyrene, a thermal insulation and waterproofing layer is simultaneously formed on the surfaces of the tape. This type is used when the building area is limited or the groundwater level is high. The advantages are obvious:

it can be quickly assembled directly on construction site, does not take up much space;
it is supplied in a factory configuration, there is no need to calculate the parameters of the panels, they can simply be cut, which cannot be done with wooden formwork;
all external and internal surfaces of the tape remain insulated;
the result is the smoothest outer surface, ready for construction and resistant to frost heaving.

The key disadvantage is the cost of permanent formwork, since it is produced in a factory from expensive materials and cannot be removed. At every individual construction you have to re-calculate the dimensions of the slabs.

Wood formwork

Metal formwork

Permanent formwork

Inspect the formworks prepared for construction wooden materials for the absence of unevenness and contamination.
The installation of the structure must be strictly level;
The fastenings must be fixed very tightly, since if this condition is not met, deformation of the future foundation may occur;
When constructing formwork, it is worth checking the surface for the absence of cracks and gaps.

Conclusion

We build a house from foam blocks with our own hands
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When constructing a monolithic foundation, it is very important to correctly position the formwork - the structure must create a rigid shape with given geometric dimensions.

The strength and reliability of the foundation support of the building directly depends on the accuracy of the alignment. This article is all about how to correctly set up the formwork for pouring foundation supports.

Which one to choose?

Permanent formwork

There are removable and non-removable formwork designs. For a monolithic foundation, it is usually made of wood, plywood or metal. Fixed forms for the foundation are made from sheets of expanded polystyrene. Expanded polystyrene is not dismantled after hardening concrete mixture– the layer serves additional insulation foundation supports (this manufacturing method is most suitable for areas with cold climates).

Assembly of foundation formwork is necessary when concreting monolithic building structures– a reinforcement cage is installed into it, a concrete mixture is poured, which, when hardened, gives the foundation structures the necessary shape and rigidity. Clearly positioned formwork panels help maintain the monolithic reinforced concrete foundation in the dimensions specified by the design.

Making wooden shields

Wooden formwork

Formwork made from wooden boards must be adjusted as much as possible, achieving minimal gaps between two boards so that the concrete mixture does not leak out of the box through existing cracks. The formwork forms must be as smooth as possible and free from flaws, in which case the finishing of the foundation walls will be very easy to achieve perfection.

Wooden formwork is made in the form of an oblong panel; during installation, the elements are fastened together using metal fasteners (nails and self-tapping screws). Wood is chosen coniferous species, planed edged boards with a thickness of 25 mm and a width of up to 150 mm are ideal.

The racks and frames of the form for a monolithic foundation are made of wooden blocks - these elements ensure the stability of the panels during pouring of concrete mortar.

It is very important to use lumber for the manufacture of formwork high humidity– this is necessary so that the wood does not absorb moisture from the concrete solution, which will greatly deteriorate the quality of the hardening concrete solution.

Installation Rules

Pouring the foundation

When installing, it is very important to follow the existing building codes and rules - this will help to pour strong and reliable foundation from monolithic reinforced concrete:

It is not allowed to install the support posts of formwork panels on dug up or fill soil; it is necessary to ensure the reliability and stability of the structure, for which, on problematic soils, it is necessary to place cuttings of boards under the support posts.
The shields must remain in an unchanged position for a sufficiently long period of time, taking into account the impact on them of the mass of concrete poured into the structure, therefore wooden formwork can be strengthened by installing braces, racks and supports.
In subsidence and heaving soils, the mold is mounted on special foundation edges buried below the freezing point of the soil.

Installation work

It is convenient to mark the formwork on the building site using pegs and stretching a construction cord or fishing line over them. It is very important to remember that the foundation should be 10-15 cm wider than the walls. Each action should be checked with a level and a laser level - this way you can ensure the most even placement of the formwork panels.

It is possible to position the formwork correctly only by using a level, which should be used to periodically check for possible displacement of the panels during installation.

You can start installing the boards only on level ground, securing each board with scraps of reinforcement and wooden support pegs. The panels are secured from the inside with reinforcing rods - after concreting, the reinforcement will serve as an additional reinforcement element to impart vertical rigidity. Watch the video on how to install formwork without mistakes.

The lower edges of the formwork panels should rest completely on the upper surface of the ground, and adjacent elements should have the closest possible fit to each other.

The side panels are tightened using special ties made of timber, which are strengthened on top of the formwork panels from above. Screeds are installed every 0.5 - 1.0 meter.

How to correctly level formwork panels

Usually the formwork rises 30 cm above ground level; it is very important to set the panels as level as possible so that there are no differences in height on the surface of the foundation. All formwork installation operations should be checked for level. It is very important to level the upper edge of the formwork, for which a stake is driven in the center of the building, on which the zero mark of the foundation is marked. Then, using a tubular level, marks are placed on the surface of the formwork panels or stakes. Concrete should be poured into the structure in accordance with the marked risks.

When the concrete mixture hardens and gains strength, the panels can be dismantled, usually 14-15 days after pouring the concrete.

When installing formwork for the foundation, it is better not to slack in the work, otherwise the durability of the built house will be at risk.

How to align formwork using a laser level?

By using laser level The formwork is placed simultaneously along the entire perimeter. The device at a distance with high accuracy projects vertical and horizontal lines visible to the eye, determining the shape of the future structure.

Possibilities of laser levels when constructing formwork

Bubble levels allow for significant error. The use of hydraulic ones is possible only in the positive temperature range. Due to the high resistance in the tubes, the liquid level is set long time. Just marking out a complex foundation can take a whole day.

It’s a completely different matter when the formwork is set using a laser level. This is especially true for models capable of projecting a 360° beam. It is enough to install such a device inside the future foundation, and we will be able to place the formwork anywhere. Several workers can start work at once without crowds. The docking of the shields will occur flawlessly.

Speaking of foundations of complex shapes, with inclined planes and edges, setting up formwork without a laser level will require painstaking and lengthy calculations and making a model of the future structure.

Laser level for home use

Professional equipment is expensive and has great functionality. For reference household Inexpensive rack and pinion models are sufficient. For advanced owners of country real estate who are actively developing their homestead farming and arranging the local area, it makes sense to opt for more expensive structures with a self-leveling mechanism. Unlike rack laser levels, where installation is carried out along an air bubble, here spatial coordination is built into the program. The self-leveling option does not allow the slightest deviation of the beam from the base projections. Read in detail modern models Laser levels can be found on the website www.laserbuild.ru.

Using a laser level to level formwork

Let's consider the possibility of using a laser level using the example of constructing formwork for a strip foundation. Professional approach consists of preparing shields that are installed in a trench, leveled and nailed together. Sequencing:

we set the level to the height of the future foundation and, by projecting a beam along the perimeter of the trench, we determine the required width of the shield;
After manufacturing the formwork walls, they are installed sequentially. We focus on the projection of the beam. We perform the leveling with pads under the bottom edge of the boards;
After installing the shields horizontally, we check the verticality of the planes. Regulation is made by spacers inside the formwork and upper ties;
After checking, the design is rigidly knocked down. If necessary, reinforcement is knitted and side slopes are attached.

It is also possible simplified version setting up the formwork, when the beam is projected onto the finished formwork. In this case, the beacons are transferred inside the structure. A wire is stretched along them, serving as a guide when pouring concrete.

How to set up formwork for a strip foundation

Reliability and rigidity, the qualities that formwork must meet, and of course, the zero-level form must be ideal. Therefore, for the geometry of the formwork, a deviation of no more than 2 mm and 3 mm is allowed for the joint gaps between the parts of the system. So today we will talk about how to set up formwork from boards for a strip foundation.

Construction device

Due to its cost-effectiveness, formwork made of wood is the most used option for installing a foundation. belt type. For the manufacture of formwork, boards and bars are used, and plywood and fasteners can also be used.

Product elements

The main parts of wooden formwork for the foundation are:

The deck is shaped like a shield and is made of boards or sheets of plywood;
The fasteners used are: screws and nails various sizes, as well as the wire necessary to tie together various elements;
Scaffolding struts, posts and frames providing lateral stability.

When choosing wood for making formwork, you should check it for bending, since the panels must retain their shape under high loads from concrete, and the boards must bend.

For the production of formwork the best option There will be planed 25 mm boards, preferably coniferous, this wood has high elasticity and strength. When assembling panels, it is necessary to use edged (edged) boards, this will reduce the gaps.

For formwork, it is advisable to use boards with a width of up to 150 mm and high humidity. Dried wood will draw moisture from the solution, and this will disrupt the natural course of hardening and affect the quality of the concrete.

Installation of formwork

Having completed the excavation work and installed waterproofing material at the bottom of the trench, we proceed to the manufacture of shields, for which we can use available materials.

Making shields

To do this, cut three-meter boards are connected to each other with wooden blocks, for fixing which you can use screws or nails. The bars should be installed at intervals of no more than 1 meter. One end of the block should have a pointed base to make it easier to drive it into the ground. When installing the bars to the shield, you should remember that the pointed ends should be directed in one direction.

The formwork parts are fixed with nails, which are located with heads on the inside of the foundation, this will allow you to obtain a foundation with smooth walls and will facilitate dismantling work.

Installation of formwork panels

The formwork must protrude at least 30 cm above the ground. To ensure high quality formwork, wooden panels must be securely fastened, since the concrete solution will exert high loads when pouring.

Ready-made panels are mounted along the entire perimeter of the foundation base. To fasten the shields, boards and bars are used, from which clamps are made. The clamp has U-shape, its vertical parts are made of a bar with a cross-section of 40 mm, and for the vertical part you can use a 25x50 mm board.

To add strength, jibs are installed in the clamps. For successful assembly, it is necessary to choose the correct length of the bars, taking into account that it should be equal to half the height of the shield. Installation of clamps is carried out at each bar that fastens the panels. When installing shields, you should strictly observe the location of the structure in the vertical and horizontal planes.

To make supports (struts), boards are used, which are installed at an angle to the connecting bars and are additionally supported by pegs. To fix the support to the beam, you can use both nails and screws. The length of the strut depends on the height of the shield and is taken to be the same.

The main requirement that the entire structure of wooden formwork must meet is the absence of large gaps between the boards. The presence of cracks will allow cement to leak, and as a result, the foundation structure will have irregular shapes.

An ideal wooden formwork can have gaps of no more than 3 mm; such gaps will quickly disappear when the mortar is poured and the wood gets wet.

If, after manufacturing, the formwork has a large number of cracks, they must be eliminated; for this, you can use roofing material or plastic film. These materials are installed on the inside of the formwork and fixed with nails or a construction stapler.

When installing the formwork, the reinforcement is being installed at the same time. After installing and fixing the formwork, its horizontalness is checked using a level. It would be useful to check the fastening of each structural element and compliance with the design dimensions.

After repeated inspections, you can begin pouring concrete.

How to place formwork under the foundation

In order to create a concrete or reinforced concrete structure, the construction of formwork is always first required. This is a temporary structure that acts as a kind of form for pouring mortar, which, when dried, becomes the foundation. And here the question arises: “How to correctly set up the foundation formwork and not make large quantity mistakes?" Here you need to show care and responsibility, having studied all the necessary rules and nuances. You can also try setting up the foundation formwork based on the videos you have watched and provided by experienced professionals.

Types of formwork

Foundation formwork is divided into two main types:

Removable, removed after the concrete mixture has completely hardened. For the manufacture of such a structure, wooden boards, shields, or metal elements are used.
Fixed ones remain with the mortar for the entire existence of the future building.

But designs also differ in the type of material used to construct them. There are metal and wooden structures. That is why, before placing the formwork under the foundation, it is necessary to finally decide on its type and the material used for this. To make the task easier, it is worth familiarizing yourself with each option in detail.