Types of floor
A floor typically provides:
- Structural support for the contents of the room, its occupants, and the weight of the floor itself.
- Resistance to the passage of moisture, heat and sound.
- A surface finish which may contribute to the look, feel and acoustics of a space.
Very broadly, floor construction tend to be solid floors, built up from the ground, or suspended floors, supported by wall structures. There are a very wide range of variations around these basic types. The intended use of the floor, its location, the structure of the rest of the building, and the required floor finish will determine which of the many variations is most suitable for a particular application.
- Sub-base: Well-compacted building rubble or loose stone-based material.
- Hardcore: Suitable filling material to make the required level, and create a solid base.
- Damp-proof membrane (DPM): An impervious layer such as heavy duty polythene sheeting.
- Concrete bed: Provides a solid level surface.
- Insulation to limit heat transfer with the ground.
- Screed: Usually a sand and cement mix laid to prepare for the installation of a floor covering.
- Finish: Such as carpet, tiles and so on.
The thicknesses of the layers and their order will depend on the specific use required and the ground conditions.
A suspended timber floor is usually constructed using timber joists suspended from bearing walls, which are then covered with either floorboards or some other for of boarding material. The joists are typically laid across the shortest span.
Ventilation may be provided to the void between the floor and the ceiling below by placing air vents/air bricks within the exterior walls, allowing air to travel from one side of the building to the other. This can, however, cause a problem of draughts, which can be avoided by installing an airtight breather membrane which will help maintain an airtight seal.
The construction of suspended concrete floors is similar to that of timber but can span greater distances, and offerings better sound insulation properties. A simple reinforced concrete flat slab is not usually economical as a suspended floor spanning over 5 m. Other soultions include pre-cast concrete planks or pre-cast concrete beams with concrete blocks laid between them. Voids can be created by beams or ribs, or cast-in holes, to house services, as well as providing support for suspended or attached ceilings.
Larger beams allow a greater span, but require greater overall depth and more complex formwork and reinforcement.
Ribbed floors use narrow-spaced shallow beams, or ribs, rather than wide-spaced deep beams. Troughed floors are ribbed in only one direction, whereas coffered or waffle floors are ribbed in two directions.
Ribbed floors have greater span and load potential per unit weight than flat slab construction.
This is a ribbed cast in situ floor with permanent formwork in the form of hollow clay or concrete pots. This creates a flat soffit, allowing the direct application of a plaster finish or dry lining. The pot voids can be used to contain small diameter services within the overall slab depth. The most common form is a one way spanning floor, although two way spanning is also possible.
A raised floor (sometimes referred to as an access floor or raised access floor) is a floor created above a solid floor slab, leaving an open void between the two. This void can be used to distribute building services. Raised floors are often found in offices, or in spaces that have a high demand for information and communications infrastructure such as data centres.
See: Raised floor for more information.
Plenums are air compartments or chambers, either above suspended ceilings, in the gap between the ceiling and the floor slab, or below raised floors in the gap between the raised floor and the floor slab. They form part of the ventilation system for the building.
See: Plenum for more information.
A floating floor is a floor that is not fixed to the layer beneath it. Floating floors are particularly common in refurbishment works, and can be used to help improve the thermal or acoustic insulation of a floor construction.
See Floating floor for more information.
Sprung floors are used for activities such as dance, indoor sports, and multi-purpose halls where specific properties of shock absorption and energy return are desirable to reduce the occurrence of injuries that may result from repeated impact or falls. They can also help maximise performance.
See: Sprung floor for more information.
The term ‘separating floor’ is generally used to describe a floor designed to restrict the passage of sound between the spaces above and below. It is most commonly used in relation to residential buildings.
See: Separating floor for more information.
 Related articles on Designing Buildings Wiki
- Floating floor.
- Floor definition.
- Floor insulation.
- Floor loading.
- Flooring defects.
- Insulation for ground floors.
- Raised floor.
- Separating floor.
- Sprung floor.
- Suspended ceiling.
- Types of flooring.
 External resources
- ‘Building Construction Handbook’ (6th ed.), CHUDLEY, R., GREENO, R., Butterworth-Heinemann (2007).
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