- The one-two-three rule
- Spoil the concrete on the floor
- Irons for the strength of the steps
- Tips from handymen
Drilling a door in a wall or modifying the ground level may require the creation of a few steps to facilitate access from one room to another. For convenience, it is better to make them concrete rather than wood.
To achieve these steps, nothing more simple.
- Just assemble boards for make a formwork to delimit the desired width, depth, and height. Then you have to prepare concrete: a mixture of cement, sand and gravel.
- Cement is a hydraulic binder, which means it hardens on contact with water.
- It is therefore necessary to mix cement, sand and gravel intimately, then add a certain amount of water to obtain a sufficiently flexible paste to be poured into the formwork.
The one-two-three rule
It is at the end of the evaporation of the water, that the concrete takes its hardness and its resistance.
If concrete dosing must be very precise for heavy load structures, for realizations such as steps, masons apply the one-two-three rule, namely: a bucket of cement, two of sand and three of gravel.
The volume of water is usually brought "in sight" during mixing, until a homogeneous paste, fairly consistent but malleable enough to be cast in a mold.
Spoil the concrete on the floor
Mixing consists in mixing the various components of the concrete at the same time as the water necessary for its setting is brought. Depending on the quantities and volumes required, it can be done on the ground (protected by a plastic tarpaulin or a flat tank) and shovel or concrete mixer, in a rotating tank driven by an electric or thermal motor.
For very large volumes, it is better to call on a company that delivers a concrete ready for use via a truck. But to make a few steps, we are satisfied with a mixing on the floor (called "in the area") or concrete mixer.
Irons for the strength of the steps
Formwork consists of making a mold, usually with boards of good thickness planed or with plywood.
To obtain a perfectly smooth surface, you can apply a finishing layer (thin plaster) in mortar. This is the solution generally used for steps.
We can then scrape, that is to say, drown metal rods (the "irons") in the concrete, at the time of casting, to give sufficient strength to a concrete element subjected to heavy loads or tensions. This operation, essential when pouring a lintel, a post or a slab of floor, is not necessary for massive steps of a width of about one meter (as here).
- Trace the profile of the steps on a plywood sheet (CTBX 15 mm thick), which will be the lateral part of the formwork (the steps protruding outside the wall).
- Cut two boards to the desired length in a width that will constitute the height of the steps (between 17 and 21 cm).
- Use the planed board for a good finish.
- Fix the boards on the sides of the mold by means of cleats, placed on the outside face of the stair nosing. Do not drive in nails completely to facilitate disassembly.
- Wet the formwork (so that the dry wood does not drink the mixing water), pour the concrete by shoveling it over the top of the formwork.
- Trowel with the trowel to distribute it.
- Equalize the surface of the steps while maintaining a recess (1 cm) from the top edge of the boards.
- This volume will be filled with a coat of finishing mortar.
- Fill the volume left empty with a fine mortar (considering the small quantity necessary, buy it in premeasured powder).
- Start smoothing with a trowel.
- Refine the smoothing of the plaster with a trowel called "smooth" with rounded edges.
- Eliminate some remaining imperfections with a foam sponge.
- For the realization of the stair nosing, pass the iron by pressing on the inner edge of the formwork board.
- Remove excess mortar with a tongue-of-cat trowel.
Tips from handymen
- In case of strong heat and exposure to the sun, spray the concrete with water or even the tarpaulin to avoid too rapid evaporation of the mixing water which would harm the grip and strength of the concrete.
- To facilitate the stripping, it is possible to coat the inside of the planks with special oil. Use a specific oil and no engine oil, as it may irreparably stain the concrete.