For the construction of a flight of stairs in a private house, monolithic concreting is often used, which requires the preparation of formwork.
Formwork is called a structure, which is a form for laying mortar, made of boards, plywood and timber in such a way that when filling the volume and hardening the concrete, a flight of stairs is obtained.
There are several types of stairway formwork.
Types of formwork
Mobile. This type involves the repeated use of standard molds for concrete casting. Used for mounting stairs in country houses of typical design.
With film overlap. Universal design coated with PVC film. It adapts to the required number of steps and can be used repeatedly.
Boardwalk. Formwork for individual construction. It is equipped for specific span sizes, used once.
General formwork design
So, how to assemble the formwork on a monolithic staircase? First of all, it is necessary to correctly make preliminary calculations, select the necessary material and tools, and already after that mount the structure.
The formwork device can be carried out as separate elements for each step, or in the form of a common frame for the entire march.
If the staircase is arranged in the span with a wall or between two walls, preliminary marking should be done directly on the surface of these elements. It is convenient to mark with a thick marker, focusing on a previously stretched bowstring. Thus, it will be easier for an amateur builder to later understand how steps and intermediate platforms should be located.
The formwork is assembled from boards and plywood with the allocation of each step. To ensure the strength of the structure, retaining bars with a cross section of 100x100 mm are installed along the entire length of the span. Wood parts are assembled using self-tapping screws using profiled fasteners.
Reinforcement is made after preparation of the wooden base.
DIY formwork
The assembly of formwork for the flight of stairs requires skill in carpentry and concrete work. It is important to responsibly consider the calculations and fitting of materials in order to ultimately get a strong and beautiful structure.
Necessary materials and tools
To perform the formwork for the stairs made of concrete, it is necessary to prepare the following materials:
- edged board, 30–40 mm thick;
- waterproof plywood 20 mm thick;
- ribbed reinforcing bar, cross-section from 10 to 16 mm;
- timber 100x100 mm;
- wood screws of various lengths.
To assemble the formwork for a monolithic staircase with your own hands, the following devices will be required:
- construction plumb;
- level;
- hand circular saw or hacksaw;
- screwdriver;
- a hammer.
Calculations
The optimal slope of the span is considered a value of 30 degrees. Typically, this angle is used to equip the entrance staircase or porch. For interior use, in order to save space, use a slope of 40 to 45 degrees. For the device stairs to the basement, you can use a steeper descent, and for interfloor climbs more smooth.
Accordingly, based on a comfortable angle, the number of steps is calculated. The height of the steps can vary from 100 to 200 mm, and the width should not be less than 200 mm and ranges from 200 to 400 mm.
The height of the steps in a private house where elderly people or small children live should not exceed 150 mm.
The specific number of steps is calculated by dividing the lift height by the required step height. If the steps of the stairs will subsequently be finished with tiles, it is necessary to take into account the thickness of the adhesive solution and the tile itself in the calculations.
Production and assembly of formwork
Based on preliminary calculations and the markings applied on the wall, a plank formwork frame for a concrete staircase is assembled, starting with side stops and stiffeners for flooring. Then the lower part of the structure is lined with plywood.
With the help of bars, boards and plywood, sawn according to a special stencil, the shape of the steps is made. All structural parts are fastened with self-tapping screws, so that subsequently it is easy to dismantle. For better adhesion of structural elements, it is desirable to use metal corners.
It is necessary to carefully adjust all the details of the structure so that when pouring the solution does not seep through the joints. It is recommended that all slots pass with mounting foam, the excess of which can be cut off after drying.
For the stability of the structure along the entire length of the span, racks of timber are installed. The specific gravity of M300 concrete is 2.5-3.0 t / m3, which gives a serious load to the wooden base of the formwork. So that the structure does not collapse under the weight of the monolith, the racks are installed through 400-500 mm, fixing each other with transverse and longitudinal ties from the boards.
Reinforcement
To strengthen the design of the flight of stairs, it is necessary to apply reinforcement. A mesh is made from a ribbed rod by welding, which is installed at a height of 2-3 cm from the surface of the formwork along the span, for which use plastic inserts or bend the edges of the rods, forming a support of the required height.
If there is a possibility of fastening to the walls, reinforcing bars are attached to embedded parts, or inserted into pre-prepared holes.
Do not overload the weight of the entire product with excessive reinforcement - it is completely possible to abandon the frame for steps, since for a private house such a design will be superfluous.
Concreting Procedure
Concreting the flight of stairs is carried out in one step. Filling begins from the bottom up, gradually filling the formwork with the solution. To obtain a more viscous consistency and strengthen the structure, crushed stone is added to the solution.
To avoid voids during concreting use a vibrator. After filling and removing voids, the solution is smoothed out and leveled.
In order to avoid drying and cracking of the outer concrete layer to a full set of strength, it is necessary to cover the monolith with a PVC film, which will make it possible to obtain uniform hardening of the mortar without cracks and chips.
Read more about the construction of concrete stairs with your own hands - in this article.
Spiral staircase formwork
To make the formwork for a spiral staircase, it is necessary to carry out each structural element separately. The device of running steps requires special preparation of the material: elements in the form of trapezes are cut from plywood, taking into account the rotation and the necessary width of the step.
The lateral curved surface of the formwork is made of plywood and boards. For structural stability, a beam with a section of 100x100 mm, which is installed in increments of 40 to 60 cm, is brought under the base of the formwork.
It is necessary to align the position of the retaining bars along a plumb line, installing them strictly vertically, so that the structure can withstand the weight of concrete. The beam is fixed with transverse stiffeners from the board, 30-40 mm thick.
Formwork removal from a monolithic staircase is carried out after a full set of concrete strength, which is 28 days. For the device of the railing, it is recommended to provide mounting holes on the surface of the steps or embedded parts.
Formwork device for the flight of stairs
To mount the flight of stairs in a country house, you must perform the following sequence of work:
- The number of steps is calculated based on the height of the lift and the available area allocated under the project for the stairs.
- Side surfaces are prepared (two boards 200 mm wide), on which the height and width of the steps are marked with a marker.
- Using lateral fasteners, lateral boards are installed, fixing the ends on the surface of the floor and the second floor (or intermediate platform).
- Using bars, boards and plywood, the base of the stairs and the shape for each step are made. Parts are fastened using self-tapping screws and profiled fasteners. It is recommended to fasten the steps together by applying a longitudinal bar through their middle. This bar may slightly interfere with concreting, but thanks to additional fixation, the steps will be the same size and the mortar will not squeeze out the limiter.
- The formwork is reinforced with timber posts, fastening them together by transverse and longitudinal ties from the board. To ensure the verticality of the supports, use a plumb line and a building level.
- To strengthen the structures, reinforcement is performed. Rods with a thickness of 10 to 16 mm are tied into a grid using wire or welding.
- The filling of the steps begins with the lowest, gradually moving up. When filling out the form with a solution, a vibrator should be used to remove air plugs. The surface of the steps is smoothed with a trowel.
- After the concreting process is completed, the entire structure is covered with PVC film so that the rise of the mortar occurs evenly.
- Formwork can only be removed after a full set of concrete strength.
- After removing the wooden parts, the concrete surfaces are cleaned and smoothed using a grinding wheel.