The device of a backfill monolithic staircase is a simple and reliable solution for a massive porch or a separate entrance to a building. Such a staircase can be made without special knowledge or skills, with your own hands. You just need a desire and a minimum set of tools.
A monolithic backfill staircase consists of a rigid brick or cinder block box, a platform and a flight of stairs. The space under the future steps is filled with sand, slag or simply excess soil in advance.
Such a staircase does not require additional formwork and supporting structures under the march. It has exceptional strength and reliability due to the fact that it fully rests on a prepared base.
A strip reinforced concrete foundation (300–400 mm thick) is arranged under the walls of the box. Optimal dimensions in terms of: march length 3 m (10 steps 300 mm each), width from 1 to 1.5 m. Step size 300×150 mm.
Where to begin
To carry out the work, you will need the usual set of tools: a concrete mixer, a perforator, a grinder, a 90 ° square, threads, usually from 2 m, hydro level.
Materials (based on 10 steps and 1 m platform, 1 m wide, two side walls):
- brick – 2 m3 (cinder block 1.8 m3)
- soil or sand for backfill – 3.6 m3
- concrete – 4 m3
- reinforcement (12) – 100 running m
- welded masonry mesh 50×50, 3 mm – 10 m2
Examples of the location of the stairs. 1 – doorway; 2 – platform; 3 – brick (cinder block); 4 – backfill (sand, soil); 5 – ladder body; 6 – foundation of the supporting walls; 7 – support wall; 8 – node A; 9 – node B
The amount of consumable will change in proportion to the number of steps (lift height).
It is not necessary to fill the foundation for the entire staircase area! The laying of the support walls along the strip foundation for waterproofing is carried out with a thickness of one brick (one of the walls will always be the wall of the building).
It is necessary to anchor the reinforcement (wire) into a static wall and lay a reinforcing mesh or wire every 4–5 rows, especially in the corners (the walls will have to withstand the load from backfill and ramming). It is advisable to apply liquid waterproofing from the inside.
The finished walls should not be lower than the future steps, their continuation can be an element of the porch architecture (pillars, railings, etc.).
The calculation of the dimensions of the stairs is carried out “from top to bottom” from the doorway. For marking you need a 90 ° piece. You can make it by fixing a small level on the long side of an ordinary steel square (with dimensions of at least 300×150 mm):
- Determine the level of the finished floor (surface of the finishing material) of the staircase.
- Determine the level of the site “on concrete” – subtract the thickness of the finishing layers. This will be the horizon of the site.
- Determine the location of the site relative to the doorway (centering, offset – depending on the purpose of the porch). Finding extreme points.
If the staircase runs along the wall, from the extreme point vertically downwards we put 150 mm downwards. This is the last riser – part of the site. If the staircase goes “forward” from the opening, the extreme points are applied to the support walls, having previously marked the platform horizon on them.
Further, with the help of a template, we postpone and outline the steps down, focusing on the level readings. Then we connect the lower corners with a line along the march. From this line, lay the perpendicular down 100 mm and draw a parallel line. The interval between these parallels is called the “body of the ladder.” The lower one will be the boundary of the backfill.
The backfill of the staircase sinus is carried out strictly not earlier than 3 days after the laying of the supporting walls! The sinus filling is carried out in layers (300–400 mm) with tamping of each layer. A manual rammer can be made by fixing the door handles on the end of a hemp with a diameter of 20-30 cm. The rammer should be operated at least 300 mm from the wall.
When using sand as a sinus filler, spillage with water is allowed (then hold for 24 hours). Waterproofing (usually polyethylene, geotextile or vapor barrier) is laid on top of the backfill so that the concrete does not mix with the soil and does not lose its qualities.
Reinforcement cage device
To tie the reinforcement with a knitting wire during reinforcement, you will need a hook, which can be made by sharpening and bending a 6 or 8 mm wire in a convenient form.
Reinforcement of the foundation under the support walls is made in the form of a beam frame – 4 working rods, distributed in space with clamps or short vertical rods.
The reinforcement frame of the stairs consists of a mesh at the base (reinforcement 12) and a mesh along the steps themselves (welded mesh 50×50, 3 mm).
For the device of the main working mesh in the middle of the body of the staircase and platform, we anchor the reinforcement mirror-like with a step of 200 mm On the releases, we tie rods with a length equal to the width of the stairs. Then we measure the length of the platform + the march and bend the solid rods at the angle of the march and install them in increments of 200 (6 pieces will be obtained per 1 meter of the staircase width).
To reinforce the steps, we bend the welded mesh in the shape of the letter G and fix it with a knitting wire to the main mesh.
Attention! Consider a concrete cover of 30-40 mm (from reinforcement to concrete surface)!
1 – welded mesh; 2 – transverse rods anchored into the support walls (step 200 mm); 3 – longitudinal reinforcement; 4 – persistent beam of the 1st stage
For the upper layer of reinforcement of the site, we anchor the reinforcement (2-3 rods on each side) below the horizon level by 40 mm and impose a sheet of welded mesh on them.
For flanging steps, we make risers, usually a strip of plywood with a width equal to the step height, sewn onto a 40-50 mm board. Either corners or bars are attached at the edges. The risers are attached according to the markings to the supporting walls of the stairs with “quick installation” dowels or in another accessible way. It is advisable to grease the plywood with used machine oil (this will facilitate disassembly). Then, along the march, along the top of all flanges, a solid board of 25–40 mm is sewn, always with an emphasis at the bottom (to keep the size). With a staircase width of more than 1.2 m, 2 boards are installed.
For the best result (quality of dry concrete) and ease of laying the mixture, we recommend using a deep vibrator (vibrator head with a diameter of 40 mm). The concrete is placed in the stairs from the bottom up. The concrete should be “steep” (dry) so that it does not flow through the tread.
When vibrating, the concrete “sits down”, filling the voids, so it is better to lay it in steps “with a slide” for the entire march at once. Vibrating should start from top to bottom. This will allow excess concrete to be driven off the steps. The platform is laid and vibrated last. The concrete surface is smoothed with trowels and trowels.
Attention! Remove all excess concrete from the formwork while it is wet.
Cover the flooded staircase with plastic (especially in the heat). Remove the flanged steps carefully after 24 hours.