Monolithic, reinforced concrete slab ceilings are flat ceilings, concreted at the construction site. In residential construction, such ceilings are often used as a supplement to rib-and-slab ceilings in small rooms, bathrooms, kitchens, in staircases, etc..
Depending on the width and length of the floor slab, they can have one main reinforcement- or two- and multidirectional (when the floor length to width ratio is less than 2). The thickness of the floor slab depends on the span, anticipated loads, assumed fire resistance and method of reinforcement.
Reinforced concrete ceilings rest on structural walls or on walls and binders. For the main beams, the heights of beams or binders supporting reinforced concrete ceilings should be taken as 1/15 span, and for secondary beams as 1/20 span.
The support depth of uni-directionally reinforced slabs should not be less than 8 cm at the backrest on a brick wall, 6 cm when resting on a wall of concrete class B-15 or higher and 4 cm at the backrest on steel beams.
Cross-reinforced slabs, in which the main reinforcement runs in both directions, rest on the walls with the entire perimeter of the floor slab. Cross-reinforced boards are used above rooms with four load-bearing walls, on which you can rest the hob (e.g. in the basement) and in multi-span systems, where the slab rests on girders supported by columns. Multi-directional reinforced slabs can have various shapes. In addition to rectangular plates, triangular plates are made, trapezoidal, colists.
For larger spans, it becomes uneconomical to use smooth plates. In large halls, in storage rooms, above the basement, e.t.c. a slab-ribbed ceiling can be used.
The slab-rib ceiling consists of a reinforced concrete slab, main beams (substrings) and secondary beams (ribs). Ribs are beams of relatively small size, on which the ceiling slab rests directly. The ribs rest on the walls and binders.
Various arrangements of ribs and girders are possible – The binders rest only on the columns (skeletal system) or on walls and pillars (mixed system). If the distance between the walls of the building does not exceed 6-8 m, the ribs rest immediately on the walls and no girders are needed (they are then usually of greater height).