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Flooring is the general term for a permanent covering of a floor, or for the work of installing such a floor covering. Floor covering is a term to generically describe any finish material applied over a floor structure to provide a walking surface. Both terms are used interchangeably but floor covering refers more to loose-laid materials.

Materials almost always classified as floor covering include carpet, area rugs, and resilient flooring such as linoleum or vinyl flooring. Materials commonly called flooring include wood flooring, ceramic tile, stone, terrazzo, and various seamless chemical floor coatings.


Subfloor construction

Floors may be built on beams or joists or use structures like prefabricated hollow core slabs. The subfloor builds on those and attaches by various means particular to the support structure but the support and subfloor together always provides the strength of a floor one can sense underfoot. Nowadays, subfloors are generally made from at least two layers of moisture plywood or composite sheeting, jointly also termed Underlayment’s on floor joists. 

Some flooring components used solely on concrete slabs consist of a dimpled rubberized or plastic layer much like bubble wrap that provide little tiny pillars for the one-half-inch (12.7 mm) sheet material above. These are manufactured in 61 cm × 61 cm (2 ft. × 2 ft.) squares and the edges fit together like a mortise and tenon joint. Like a floor on joists not on concrete, a second sheeting underlayment layer is added with staggered joints to disperse forces that would open a joint under the stress of live loads like a person walking.

Three layers are common only in high end highest quality construction. The two layers in high quality construction will both be thick 19.1 mm (3⁄4 inches) sheets (as will the third when present), but the two layers may achieve a combined thickness of only half-that in cheaper construction — 12.7 mm (1⁄2 in) panel overlaid by 6.4 mm (1⁄4 in) plywood subflooring. At the highest end, or in select rooms of the building there might well be three sheeting layers, and such stiff subflooring is necessary to prevent the cracking of large floor tiles of 22.9–25.4 cm (9–10 inches) or more on a side, and the structure under such a floor will frequently also have extra 'bracing' and 'blocking' joist-to-joist intended spread the weight to have as little sagging on any joist as possible when there is a live load on the floor above.

In certain parts of the World only a few rare floors will be seen to have no separate floor covering on top, and those are normally because of a temporary condition pending sales or occupancy; in semi-custom new construction and some rental markets, such floors are provided for the new home buyer (renter) to select their own preferred floor coverings usually a wall to wall carpet, or one piece vinyl floor covering. Wood clad ('Hardwood') and tile covered finished floors generally will require a stiffer higher quality subfloor, especially for the later class. Since the wall base and flooring interact forming a joint, such later added semi-custom floors will generally not be hardwood for that joint construction would be in the wrong order unless the wall base trim was also delayed pending the choosing.

The subfloor may also provide under-floor heating and if floor radiant heating is not used, will certainly suffer puncture openings to be put through for forced air ducts for both heating and air conditioning, or pipe holes for forced hot water or steam heating transport piping conveying the heat from furnace to the local room's heat exchangers (radiators).

Some sub-floors are inset below the top surface level of surrounding flooring's joists and such subfloors and a normal height joist are joined to make a plywood box both moulding and containing at least 5 cm (2 inches) of concrete (A 'Mud Floor' in builders parlance). Alternatively, only a slightly inset floor topped by a fibrous mesh and concrete building composite floor cladding is used for smaller high quality tile floors—these 'concrete' subfloors have a good thermal match with ceramic tiles and so are popular with builders constructing kitchen, laundry and especially both common and high end bathrooms and any other room where large expanses of well supported ceramic tile will be used as a finished floor. Floors using small (4.5 in/11.4 cm and smaller) ceramic tiles generally use only an additional 1⁄4-inch (6.4 mm) layer of plywood (if that) and substitute adhesive and substrate materials making do with both a flexible joints and semi-flexible mounting compounds and so are designed to withstand the greater flexing which large tiles cannot tolerate without breaking.

Ground floor construction

A ground-level floor can be an earthen floor made of soil, or be solid ground floors made of concrete slab. Ground level slab floors are uncommon in northern latitudes where freezing provides significant structural problems, except in heated interior spaces such as basements or for outdoor unheated structures such as a gazebo or shed where unitary temperatures are not creating pockets of troublesome melt-waters. Ground-level slab floors are prepared for pouring by grading the site, which usually also involves removing topsoil and other organic materials well away from the slab site. Once the site has reached a suitable firm inorganic base material, it is then graded further so that it is flat and level. Finally it is topped by spreading a layer-cake of force dispersing sand and gravel.

Deeper channels may be dug, especially the slab ends and across the slab width at regular intervals in which a continuous run of rebar is bent and wired to sit at two heights within forming a sub-slab 'concrete girder'. Above the targeted bottom height (coplanar with the compacted sand and gravel topping) a separate grid of rebar or welded wire mesh is usually added to reinforce the concrete, and will be tied to the under slab 'girder' rebar at intervals.

Upper floor construction

Floors in wooden framed homes are usually constructed with joists centred no more than 41 centimetres (16 inches) apart, according to most building codes. Heavy floors, such as those made of stone, require more closely spaced joists. If the span between load-bearing walls is too long for joists to safely support, then a heavy crossbeam (thick or laminated wood or a metal I-beam or H-beam) may be used. A "subfloor" of plywood or wafer-board is then laid over the joists.


Wooden floors, particularly older ones, will tend to 'squeak' in certain places. This is caused by the wooden floors components (boards, joists, beams) rubbing up against one another. Firmly securing the pieces to each other with screws or nails will remove this problem.

Floor vibration is a particularly annoying problem with floors. Wood floors tend to pass sound, particularly heavy footsteps and low bass frequencies. Floating floors can reduce or eliminate this problem. Concrete floors are usually so solid they do not have this problem, but are also much more expensive to construct, and much heavier, resulting in further requirements regarding the structure of the building.

For certain types of flooring protection may be required (e.g., a gym floor used for a graduation ceremony). A Gym floor cover can be used to reduce the need to satisfy incompatible requirements


Special tools used for flooring include:
  • Flooring clamp, a clamp for tongue-and-groove floors while nailing
  • Knee kicker, used to position carpets precisely and stretch small areas, like steps
  • Concrete moisture meter used to check a concrete floor before laying flooring on top