Overlappings – the designs separating the building on height. They have to conform to increased requirements to durability and rigidity, to maintain heavy loads, not to cave in under the influence of weight.
1. Overlappings are interfloor, basement, garret. According to the constructive decision they can be separated into the frame, consisting of cross logs and fillings, and on girderless, carried out from plates or panels. In low construction joist ceilings are more often used.
2. The basis of such designs is formed by the bearing cross-pieces which make of tree, metal, reinforced concrete. They are stacked with equal step from each other, the space between them is filled with setup boards. Joist wooden ceilings are usually applied in frame and wooden houses, it is necessary to calculate beam section only correctly. Their shortcoming: the combustibility, restrictions on flight width, length of beam is no more than 6 meters. Advantage – for laying is not required the special equipment.
3. Metal beams (channel, double tee, corners) reliable and durable, them it is possible to block long flights, but also they have minuses - the lowered warm and insulating properties, besides cost much, for this reason seldom apply them. With metal crossbeams use the facilitated reinforced concrete slabs or wooden boards.
4. Reinforced concrete beams can be stacked on flights 3−7.5 meters wide. The weight of these beams big, from 170 kg to 400 kg, for their mounting is required hoisting crane. The interframe space is filled with easy concrete slabs or hollow blocks.
5. Girderless designs are the panels laid densely to each other or plates which at the same time are both the bearing, and protecting elements. Types of flat slab floors: monolithic, assembly and monolithic and assembly. Precast structures from reinforced concrete apply at construction of brick houses. They are calculated on heavy loads, over 200 kg/sq.m. Do not avoid damp, are durable. The shortcoming – when mounting is required the load-lifting equipment and it is not always possible to find the necessary size of panels, they are manufactured according to the standard.
6. Monolithic overlapping – heavy, 1 sq.m at thickness of 20 cm weighs 500 kg, mounting difficult, the device of suspended formwork, placing of bars is required. Advantages – continuous concrete surface, without seams. More facilitated modern design − combined and monolithic overlapping. On framework beams keep within, between them hollow blocks and from above this construction it is filled in with thin concrete layer. Shortcoming – heavy manual process of mounting, at low construction such overlapping is inexpedient.