Reinforced concrete staircases are massive and durable. They can be finished with ceramic tile or stone, but the most popular option is wood. Reinforced concrete stairs must be properly connected to the ceiling. We will explain you how such connection should look like for monolithic, ribbed and prefabricated ceilings. The popularity of reinforced concrete staircases doesn’t decrease despite the fact that an increasing number of modular stairs are sold faster (for example, metal and wood staircases, as they are easier to install, and most importantly, don’t require any finishing). How to connect a staircase to the ceiling?
So, what’s the secret of their popularity? Of course, their massive and solid structure, which will not start to crack or bend after a few years (in contrast to the wooden stairs). It is also important that reinforced concrete allows you to build the stairs of almost any size and shape. These staircases are made of concrete, suitably reinforced with steel fittings. They are erected during masonry work, carried out in a newly constructed house. The formwork is assembled first. Then they put reinforcement and lay concrete on it. The latter takes place simultaneously with the concreting of the ceiling (which can be monolithic, filigreed, or thick ribbed). Later, at the stage of interior decoration, stairs get a wooden, ceramic or stone lining. Railings are installed as well. Reinforced concrete stairs must rest on a separate foundation and be connected to the ceiling. How can you do it? Everything depends on the type of floor.
How to build monolithic reinforced concrete stairs?
Monolithic reinforced concrete stairs must be made according to the project. A concrete of grade C20/25 or higher must be used in their production. The stairs are concreted from below, step by step, filling the mixture with the pre-prepared formwork. It is better to use plywood or OSB panels for the construction of the formwork, as it makes it easier to provide a correct level and shape for the future mechanisms, steps, and platforms. Some companies manufacture stair formworks to order. They create separate elements with computer accuracy, and then collect them within a few hours. Such service is expensive, but it allows creating an unusual and complicated shape of the reinforced concrete staircase.
Once the concrete is in place, it should be compacted (as soon as the air bubbles are gone). Later, the concrete should be sprayed with water and protected from strong sun. The geometry of the steps of the internal staircase must be determined by the condition given by the formula: 2h + s = from 0.6 to 0.65 m, where “h” is a height of the step, and “s” is its width. During some time, separate investors can also order the prefabricated reinforced concrete stairs manufactured in the factory based on their project, and then transport them to the construction site by trucks and install them on-site using a crane.
Combination with a monolithic ceiling
Monolithic reinforced concrete ceiling is built entirely on the construction site. Its characteristic feature is the ability of using the complex shapes and large cubic capacity in buildings. It must be made according to an individual project developed by a civil engineer. Unlike thick-walled or prefabricated structures, it can have different thicknesses. It depends on its span, the amount of reinforcement and loads and usually ranges from 15 to 20 cm. A monolithic ceiling is usually formed as a flat reinforced concrete slab without beams. After that, bi-directional strengthening is performed, which is created by laying the reinforcing bars in the form of a mesh. The location of the stairs in the reinforced concrete monolithic ceiling is optional. When reinforcing the ceiling, contact rods must be placed at the edge of the opening that will be connected to the stair reinforcement. It will unite these elements forever. The bars are used in the same quantity and diameter as the reinforcement of a stair slab. They should fall into the ceiling at a distance equal to 40 rod diameters.
Stairs can be concreted simultaneously with the ceiling using the accumulated equipment (a pump or a vibrator). The edge of the hole in the ceiling must be closed with so-called “hooks”, i.e. U-shaped reinforcing bars connecting the upper mesh to the lower one. At the point of connection with the staircase, the edge of the slab is reinforced with additional bars hidden in its thickness. In case of monolithic or composite floor, the combination of purlin reinforcement and floor slab reinforcement requires special precision.
Combination with a ribbed ceiling
Truss beams are the main structural element of the ribbed ceiling. Ceiling blocks are supported on them, which (unlike beams) don’t have a structural function. They are only the filler. Besides, beams are made in certain places called “distribution ribs”. A concrete layer is made on top of such ceiling. Floor beams are very important. Their axial distance depends on the type of floor and its load-bearing capacity. Usually, it varies from 45 to 60 cm. The denser their distance and the thicker the floor, the higher the bearing capacity of the floor. In single-family homes, the ceilings are designed for a payload of 150 kg/m2. To base the run of monolithic stairs on the ceilings of this type, it is necessary to make holes for reinforced concrete reinforcement at the edge (foundation). They can be replaced with multiple floor beams, situated next to each other. The number of beams or beam reinforcement and its cross-section must be defined in the structure. The longitudinal reinforcement of the stair is supported by these beams, which will then be fixed in the upper concrete layer.
Combination with a composite floor
Filigreed or vector ceilings are called composite floors. They are made from 5-7 cm thick precast concrete slabs, made according to a specific project. These slabs form the formwork on which the concrete mixture is later applied. They also contain all bottom reinforcement in the form of steel bars or cells, while the girders protruding above their surface facilitate the connection with the concrete layer. If necessary, additional reinforcement can be placed in concrete. Stair supports are made in the same way as monolithic ceilings (laying of anchor reinforcement on the precast panels).
Combination with a prefabricated ceiling
Precast ceiling is usually made from channel slabs (reinforced or pre-stressed concrete) in the production slabs. Slabs of certain sizes are sent to the construction site and mounted with a crane. The most important advantages of such ceilings include a simple and fast installation. A place for staircase support can be provided in the channel slab (however, it must be already reinforced at an appropriate stage). More often, however, an additional reinforced concrete element is reinforced at the construction site. It is also possible to make a monolithic ceiling slab in the area where the ceiling is connected to the staircase at the base of the staircase walls. This solution is often used in the apartment buildings, where the staircase is divided by walls due to fire safety requirements. The principle of manufacturing restorations is similar to that of monolithic ceilings. Prefabricated channel ceilings make it possible to use prefabricated staircases that will lean directly on the panel locks. This solution allows you to fully use the potential of this ceiling, namely, to reduce the implementation time and minimize concreting work at the construction site.