Circular formwork for foundations

Varieties of formwork for strip foundations

Basically, one of two types of construction is used - collapsible or non-removable. Each of the options has its own advantages and disadvantages, which must be taken into account when choosing, therefore, you need to consider both formworks in more detail:

• Collapsible. Formwork of this type is disassembled upon completion of the solidification of the poured concrete solution for the foundation of the structure. In the future, all of its elements can be reused for this task. In most cases, wood is used to create structures. Much less often they are made of plastic and metal shields. Regardless of the material that is preferred, as a result, the formwork must have tight seams and ensure a reliable connection of the constituent components. Fixed structures are suitable for pouring foundations of varying complexity. They are also often used in the creation of individual building elements, such as walls and ceilings.
• Non-removable. Unlike the previous version, these formworks are not disassembled after pouring and hardening of the concrete solution, which saves time on their dismantling. They differ in manufacturability and have a number of positive aspects in comparison with non-removable structures. Formwork of this type is made from polymeric materials of various technological levels.
  Most often, when creating, due to its affordable cost, polystyrene is used. Fixed formwork is perfect for monolithic structures.

Note! Non-demountable structures perform a heat-insulating function, providing protection of the foundation from the effects of low temperatures.

If there is no soil shattering at the site of the building's foundation, and it also has optimal strength and viscosity, then it is possible to pour concrete solution directly into a previously dug trench for it without creating formwork, thereby reducing material costs, and, accordingly, overall costs.

DIY foundation: simple solutions for formwork installation

The house starts from the foundation. Making it with your own hands is not difficult, experts say and give their advice on the step-by-step installation of formwork - a key element of the future foundation of the house. An article, as well as photos and videos, will help you understand the recommendations.

How to choose formwork

In order for the concrete support of the building to become strong and monolithic, the builders came up with formwork.

It can be temporary or permanent, made of wood or polymers, but its main tasks remain unchanged:

• create and maintain the shape of the above-ground part of the concrete strip foundation;
• be as smooth as possible from the inside in order to minimize subsequent finishing work on the surface of the structure;
• to cope with the loads when pouring and compacting concrete mortar;
• quickly assemble and disassemble;
• if necessary, isolate concrete from soil and other negative factors.

Construction of wooden formwork

In order for the installation to go smoothly, and you do not have to solve unexpected problems, before starting work, you need to make sure that there are five main conditions:

1. The soil on which the base is poured must be completely free of debris and various impurities.
2. The panels on the inside should have as flat and clean surface as possible in order to reduce finishing work.
3. The formwork fasteners must withstand the pressure of the concrete and not deform.
4. Maximum contact between the shield components is required to prevent leakage. For this, the clarity of the geometry of the edges of the structure is important.
5. If the shuttering boards are reused, it is necessary to clean the entire working surface from the remnants of the previous mortar.

Removable formwork: time-tested installation

Mount, pour, hold and remove - this is a short recipe for installing removable formwork. Its most popular variety - wooden - is as old as the concrete foundation. It is not difficult to make such a formwork. Shields are made outside the construction pit from boards and sawn timber of the required dimensions. The boards are edged, since it will be necessary to fit them tightly to each other.

Attention! Slots up to 3 mm in timber formwork are considered the norm. As a result of preliminary wetting, the boards will swell and the distance will decrease

If the slots are larger, up to 10 mm, they must be closed with tow, and the very large ones must be filled with slats.

Pouring solution

It is better to sharpen the bars at one end, then they will easily enter the ground. To fix the formwork panels at the same distance, wire twists, struts, frames, wooden ties are taken.

The final step in the installation of wooden formwork is to secure the panels in the trench using spacers: wooden stakes or bars. After pouring and ramming, the concrete is cured in the formwork for up to two weeks, until it hardens and gains strength. After that, the structure is dismantled. Plywood formwork is installed according to a similar principle.

Attention! It is advisable to isolate the removable formwork from concrete with special compounds against the adhesion of materials.

Fixed formwork for foundations: a new word in construction

In recent years, the removable structure has been replaced by a structure using polymer formwork, which, after pouring concrete, becomes part of the future foundation. It gives it additional properties, protecting it from water and keeping it warm. Additional properties of permanent formwork made of such a material: ease of assembly (somewhat reminiscent of a constructor or a puzzle) and, as a consequence, the geometric harmony of parts. Certain types of polymer formwork have a reinforcing mesh that reinforces the foundation.

Fixed formwork

Of the minuses, the cost of such a foundation is higher than that of a foundation built with the help of boards. However, the game is worth the candle when it comes to what is being built for decades and for yourself. Permanent formwork can also be made of galvanized profile sheet - in the finished foundation, it will protect the concrete surface, and its waves will serve as stiffeners. In addition to such a metal structure, a removable "belt" of stakes from a bar is required.

We mark the site for the strip foundation.

Before you start marking, you should remove vegetation from the entire perimeter of the territory allotted for future construction. After that, we designate the outer edges of one of the outer walls of the foundation with two U-shaped structures consisting of two pegs driven vertically into the ground and one bar nailed over the pegs. Pull the rope between these structures.

The perimeter is marked, it's time to tackle the internal partitions. The ropes should be pulled parallel to the threads that mark the edge of the foundation. Observe the angles, they should all be 90 degrees. The distance between the threads should be equal to the width of the walls of the future foundation.

Now it's time to take up the shovel - we will dig trenches along the lines marked with ropes. The width of the dug trenches should exceed the width of the walls of the future foundation, compliance with this condition will allow us to make the device of the strip foundation formwork according to the rules.

Deep in the trench should go by an amount composed of compacted layers of sand and crushed stone 15 cm each and the depth of the foundation.

Varieties

Like other systems, rounded formwork structures are divided into:

reusable. Can be reused and assembled directly at the workplace.Concrete is poured into the prepared form, after it has solidified, the formwork is dismantled. Sometimes an inconvenience arises when the formwork structure is lower in height than the project requires. In this case, it is necessary to top up the structure, which entails a weakening of solidity. One of the examples of such a design is the self-made formwork for the rings of reinforced concrete;

• non-removable formwork. More expensive designs, but this is their only drawback. This concreting technology significantly improves the quality condition, gives the structure stability, extends its operational life;
• disposable. For manufacturing, pressed cardboard is used. The base is impregnated with a special glue, due to which additional strength is given to the formwork elements. The diameter of such formwork is different, ranging from 0.2 to 1.2 m. The inner wall can be left smooth, or a patterned relief can be arranged. After the poured mixture has completely solidified, the cardboard is removed.

Formwork assembly instructions

The above is a general instruction for the installation of formwork of any structure. But when assembling forms for the foundation, walls and floors, there are special nuances that you definitely need to know about.

Of the foundation

When installing formwork for a strip foundation, shields made of boards or plywood are often used. It is these elements that take on the main load exerted by the concrete solution.

The strength and service life of the entire building depends on how correctly the formwork for the foundation is assembled, since the foundation is its basis. Before starting the construction of the foundation, it is necessary to carry out a number of preparatory measures.

At the initial stage, it is necessary to become familiar with the requirements of the project, in addition, it is necessary to take into account the climate. Carry out work, preferably at positive temperatures, that is, in late spring or summer, when frosts are unlikely

If you plan to build the most common formwork from boards, then the procedure should be as follows:

• on the prepared site, the corners of the foundation to be poured are marked. The rest of the elements will be attached to these bars;
• the distance between the bars is measured and, depending on the results obtained, the boards are assembled from the boards;
• knock together shields with the help of bars, which must remain on the outside of the forms;

• shields are made in duplicate, since these elements are installed opposite each other;
• the shields are sealed, in addition, their inner surface is treated, it should be as smooth as possible;

shields are installed between the corner bars, securely fastening the elements to each other. From the outside, they are strengthened by installing mows. The spacing of these elements depends on the thickness of the foundation and ranges from 0.5 to 1 meter. Inside, the shields are fastened by installing screeds.

the inner part of the assembled formwork forms is lined with a dense polyethylene film or roofing material, the waterproofing material is fastened with self-tapping screws. This will help prevent the solution from leaking out through the cracks. It is recommended to pour crushed stone or sand at the bottom of the molds so that the liquid from the solution is not absorbed too quickly into the soil;

before pouring the mortar, it is necessary to check the horizontal and vertical position of the installed elements again.

Sten

When assembling the formwork for the construction of walls, the installation technology differs little from the technology for assembling the foundation forms. Two types of wall formwork are used:

• small-panel - assembled from relatively small panels made of laminated plywood or plastic. This equipment is suitable for the construction of small objects such as low-rise buildings;
• large-panel - differs in the presence of large-area shields. It is used for the construction of large objects, for example, multi-storey buildings.

The distance between the boards depends on the thickness of the walls. When assembling forms, the need to leave openings for windows and doors should be taken into account. The boards are disassembled after the concrete solution has completely solidified.

Overlaps

When installing floor formwork, horizontal forms are collected at a height. The installation option depends on the planned ceiling height. Most often, structures on telescopic racks are used, they can be used if the ceiling height does not exceed 4.5 meters.

Tripods are mounted at the bottom of the struts for stability, and universal forks are attached at the top. These forks are used to anchor the load-bearing beams on top of which the cross beams are laid.

The horizontal part of the form - the deck - is laid on top of the beams. And along its perimeter, vertical sides are installed, their height depends on the design thickness of the floors.

Non-removable

Installation of fixed formwork is easier than assembling movable forms. For the assembly of non-demountable formwork, special blocks of expanded polystyrene are produced. Other material options are much less commonly used - reinforced concrete, wood concrete, metal.

Styrofoam blocks are installed on a previously prepared base. If this is wall formwork, then they are placed on a finished foundation covered with a layer of waterproofing. The blocks are mounted on top of the reinforcement rods protruding from the foundation. Lateral connection of adjacent blocks occurs due to the fasteners available on them.

So, installation work on the assembly of the formwork is an extremely important stage in the construction of a building. Not only the appearance of the cast structure, but also its strength characteristics directly depends on the quality of the work performed.

Therefore, the installation must be treated with special attention and all technological requirements must be met carefully.

Types of circular formwork

Of course, a unique and original home of your own is wonderful. Especially when you can use unique architectural forms and non-trivial building elements. Therefore, circular foundations are popular, the formwork for which can be made by hand in a matter of days.

But now there are two main options for formwork for such bases: removable and non-removable. As a rule, removable formwork is used many times, its role is to preserve the round shape of the future foundation and, when the concrete hardens, it was possible to dismantle the formwork and move it to another place.

Reusable formwork is often used in the construction of column bases, made from various materials, even plastic or wood.

How to make a non-removable structure:

• Factory polystyrene foam box. It is produced in various sizes and thicknesses, it is flexible and here you just need to assemble the finished structure right on the spot;
• Profiled sheet of small thickness, which is easy to bend without breaking;
• Thin sheet steel.

Types of structures - pros and cons

To significantly simplify and speed up the process of installing the formwork for the strip foundation, as well as the construction of the building itself, you can rent a device in a construction company. We are talking about prefabricated formwork structures, which are easy to assemble. As a rule, the dimensions on such products have already been set, it remains only to install the formwork on your site.

Metal construction

Very convenient and easy to use. The elements to be installed are fastened to each other with bolts. Formwork takes much less time, in contrast to the installation of wooden panels, which require a preliminary calculation of the strip foundation formwork.

Metal shields are more durable, they guarantee a smooth and even surface, but they are used, as a rule, in large constructions - construction companies, since in some cases this option is economically unprofitable.It is not profitable if you buy metal formwork even for the construction of a two-story house, you can win if you rent a product, again - it all depends on the prices of the supplier company.

Fixed types of formwork

Formwork for a strip foundation is of a non-removable type. Elements of this structure are hollow blocks, often in a U-shaped configuration. Molds are poured from expanded polystyrene, cellular types of concrete. These products have a definite plus in terms of thermal insulation.

The strength and speed of assembly is due to the groove joints. Fixed structures of this type have one significant drawback - they are very expensive and more suitable for large developers, and are not very popular among private builders.

For a do-it-yourself foundation, this option - cellular concrete is hardly suitable, besides, some products are heavy, which makes it difficult to build on your own. Formwork walls made of expanded polystyrene are also expensive. As a plus, we can assume that the foundation will not freeze, as well as the fact that everything is offered for the assembly of the formwork:

• expanded polystyrene plates;
• corner turns;
• spacers;
• clamps;
• reinforcement rods.

In the case of expanded polystyrene plates, all that remains is to know how to correctly position the formwork elements and you can start assembling the structure. Specialists from construction companies can easily cope with such work, but not every private house builder can afford to hire them, as well as buy ready-made fixed formwork.

Plank formwork

The most popular option for assembling formwork with your own hands from a board. As a rule, private developers assemble and customize formwork boards right on their site. You can also order in the carpentry shop, after calculating the dimensions of the future structure.

Do not forget that there is SNiP, which regulates the standards of formwork deflection. According to the existing standards for formwork, the deflection is on average 1/350, while for the underground part it is increased. For non-professionals, advice - in creating formwork from boards, as well as from any other material, fastenings, walls are best done with a margin of safety.

Pour the mixture into the formwork

The mixture is poured over the entire perimeter of the foundation at once. Pouring in layers will result in insufficient concrete strength. Of course, it would be optimal to order the mixture at the production site - they will bring you the required amount of concrete, prepared in full compliance with the required proportions.

If, for some reason, you cannot do this, you will have to do it on your own and with a concrete mixer.

All components must be free of clay and other foreign elements. Of course, the water must also be clean. The optimal brand of cement is considered to be 500, you cannot take below 400. The higher the cement grade, the more durable the concrete will be. In addition, the time of its solidification is much shorter.

Please note that the resulting mixture should be plastic. For orientation - for a cube of concrete, you have to spend five bags of cement, ten bags of sand, thirty bags of crushed stone. Further, the mixture poured into the formwork must be tamped. For this manipulation, you will have to rent a deep vibrator from a construction company.

In hot weather, the concrete surface must be moistened from time to time - this will help you avoid the formation of a crust that prevents the deeper layers of the foundation from hardening. If the weather is rainy, cover the foundation with a film, otherwise it may get wet.

Although the manufacture of formwork for a strip foundation is quite a laborious process, you can cope with it.

From an engineering point of view, no specialist will be able to calculate the formwork absolutely precisely: too many variable objective and subjective factors affect the structure.

Let's name just a few of them.

1. The quality of the lumber.
   In nature, there are no two completely identical boards. The strength of sawn timber depends on malformations, the number, nature and specific location of the knots, etc.
2. Indicators of concrete.
   Concrete can have a different consistency in terms of viscosity, it depends on the proportions and characteristics of the fractions used during preparation. In addition, the loads on the formwork vary depending on the pouring speed of the concrete, the ramming method and the availability of reinforcement.
3. Climatic conditions.
   At subzero temperatures, the boards have some indicators of physical strength, in summer others. Dry boards can withstand higher forces, while in rainy ones their strength decreases.

There are building standards that regulate the maximum deflection of the formwork. For the aboveground part of the foundation, the deflection should not exceed 1/400 of the length; for the underground part, the standard is increased to 1/250 of the length. It is difficult for non-professionals to achieve such values. What should ordinary developers do? During the creation of the formwork, you need to be guided by the advice of experienced builders and your intuition. And remember the main rule - it is better to do any formwork with a clear margin of safety, do not rely on "maybe it will withstand".
It must be remembered that it is very difficult and expensive to correct violations of the linearity of concrete.

First, you should know for what purpose you need formwork. If you plan to use it repeatedly, then you should use a special laminated waterproof plywood or knock down standard shields from high-quality edged boards.

Film faced plywood formwork

If the formwork is for one-time use, then low-quality materials will be used; under certain conditions, you can use pieces of chipboard, ordinary plywood or even unedged boards. As a rule, for the construction of a bath, you can choose the cheapest formwork manufacturing option.

By design features, the formwork can be:

Formwork types

Small-panel formwork

During the construction of objects erected using different technologies, it is allowed to use several types of formwork:

• Small-panel - this type of formwork consists of small segments with a surface area not exceeding 3m2. Weight - up to 50 kg. The unified dimensions of the small-panel formwork make it possible to use the structure when concreting any objects of monolithic construction, but most often the panels are used for pouring small structures of a non-standard sample in a monolith.
• Large-panel - used for pouring monolithic wall structures, long arched and tunnel vaults (floors), as well as concrete industrial pipes and cooling towers.
• Block-form - the structure is used when erecting small vertical and horizontal volumetric surfaces from a monolith.
• Sliding formwork - used for casting wall structures in buildings of considerable height.
• Block - formwork of this type is used in the construction of a block of premises (walls being erected simultaneously without a ceiling device).
• Pneumatic formwork - used for the construction of curved surfaces of small dimensions, work is carried out using compressed air pressure.
• Fixed shields (sheets) - used to create additional insulation of building structures, to increase the protective waterproofing properties of building units.

Fixed formwork

The new technology of pouring foundations and erecting walls is characterized by excellent operational characteristics and, unfortunately, the same high price indicators. Significantly speeds up the construction process, plays the role of not only formwork, but also insulation. It is often used for the construction of monolithic earthquake-resistant reinforced concrete buildings. Bearing walls are not only durable, but also insulated.

Construction companies produce permanent formwork from various materials and with different linear parameters. The specific type of formwork should be selected taking into account the place of its use. There are several types of permanent formwork.

1. Made of highly durable expanded polystyrene foam. Represents flat plates or blocks, corner turns, spacers, reinforcement clamps, etc. The thickness of the sidewalls can be from 40 to 100 mm. The process of assembling formwork blocks is carried out in tenons, all dimensions must be checked with a level. Depending on the height of the formwork, concrete is poured in several layers along the entire perimeter of the foundation or wall. After pouring the previous layer, several rows of formwork are again assembled and the next one is poured.

2. Permanent concrete formwork. It is made of durable concrete, the side surfaces of the blocks have spikes and grooves for a strong connection to each other. The walls are held in place by bridges. Such formwork can be used both for pouring foundations and for erecting monolithic reinforced buildings. The reinforcement does not fit, the vertical rods are inserted into the holes, and the horizontal ones rest on special stops.

3. Wood concrete. It can be in the form of hollow blocks or flat panels, the front surfaces must be finished, it is used only for the above-ground part of the foundation or walls. The blocks are installed using the dry masonry method; fittings may be inside. The panels are assembled on screeds installed inside the concrete. The front surfaces of the screeds are in the form of large flat washers, the surfaces of the panels are characterized by high adhesion to all building finishing materials.

It is not economically feasible to use such expensive formwork on the strip foundations of the bath. Baths do not need an insulated foundation, and the basement visible part will get off with ordinary decorative materials.

Materials used for the manufacture of formwork

As mentioned above, any material can be used to make the formwork that can withstand the loads that arise when pouring concrete.

Before asking the question - how to correctly make the formwork for the strip foundation - you should familiarize yourself with its existing options.

Wooden formwork

The most common type of formwork is a structure assembled from wooden panels. Their deck consists of several planks, fastened together by vertical elements made of wooden blocks.

The thickness of the board is chosen by the calculation method, or it is taken on the basis of the experience accumulated by the builders (the choice of the board for the foundation formwork). The consumption of the board depends on the height of the monolith.

The need for vertical elements of the product is influenced by the thickness of the deck - the thinner the board, the smaller the step will have to be maintained between the beams. On average, the distance between them does not exceed one meter.

Metal formwork

Galvanized steel or aluminum alloy is used for the manufacture of metal formwork. Steel structures are characterized by high strength properties, do not deform and perfectly withstand all types of loads in the process of pouring concrete mass - dynamic and static.

Aluminum formwork is practically in no way inferior to steel, while possessing very positive properties:

• light weight, which allows a private builder to do without construction equipment;
• high corrosion resistance.

How to make metal foundation formwork? It can be purchased at a hardware store. Purchased metal formwork is a set of elements, from which the structure is quickly assembled at the construction site.

Factory products are distinguished by the accuracy of execution, which has a very positive effect on the quality of the foundation.Hand-assembled metal formwork cannot boast of such qualities - a private builder usually assembles it from steel sheets at hand.

In such conditions, it is difficult to comply with the permissible deviations - no more than 2 mm in linear dimensions. Nevertheless, when erecting non-critical structures - fences, gazebos, etc. - formwork of quite acceptable quality can be built from steel sheets.

Expanded polystyrene

What to make the formwork for the foundation so that it simultaneously performs the function of thermal insulation? The cheapest material suitable for solving this problem is expanded polystyrene (foam).

Factory polymer formwork is produced in the form of hollow blocks, from which a structure of any shape can be easily assembled - from rectangular to round or oval. Individual elements of the fixed formwork are equipped with special locks, with the help of their tight connection (fixed foam formwork for the foundation).

The question of how to correctly make a formwork for a foam base is usually not a question for amateur builders: they need to calculate the required number of blocks, buy and assemble them according to the manufacturer's instructions.

You don't have to make any adjustments to the parts.

Installation of permanent formwork for the foundation