Editing Floor (section)

== Subfloor construction ==
Floors may be built on [[Beam (structure)|beam]]s or [[joist]]s<ref>{{Cite book|url=https://books.google.com/books?id=9ZDpdupFBoQC&q=%C2%A0Floors+may+be+built+on+beams+or+joists&pg=PA19|title=Wood Frame House Construction|last=Anderson|first=L. O.|date=April 2002|publisher=The Minerva Group, Inc.|isbn=9780894991677|language=en}}</ref> or use structures like prefabricated [[hollow core slab]]s. 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-resistant ("AC" grade, one side finished and sanded flat) [[plywood]] or composite sheeting, jointly also termed ''Underlayments'' on floor [[joist]]s of 2x8, 2x10, or 2x12's ([[Lumber#Dimensional lumber|dimensional lumber]]) spaced generally on {{convert|16|in|cm|1|adj=on}} centers, in the United States and Canada. 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 {{convert|1/2|in|mm|1|adj=on|spell=in}} sheet material above. These are manufactured in {{convert|2|x|2|ft|cm|0|abbr=on}} 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 highest-quality construction. The two layers in high-quality construction will both be thick {{convert|3/4|in|mm|1}} sheets (as will the third when present), but they may have a combined thickness of only half that in cheaper construction{{snd}} {{convert|1/2|in|mm|1|abbr=on}} panel overlaid by {{convert|1/4|in|mm|1|abbr=on}} plywood subflooring. At the highest end, or in select rooms of the building there might be three sheeting layers, and such stiff subflooring is necessary to prevent the cracking of large floor tiles of {{convert|9|-|10|in|cm|1}} or more on a side. The structure under such a floor will frequently also have extra "bracing" and "blocking" joist-to-joist intended to spread the weight to have as little sagging on any joist as possible when there is a live load on the floor above.

In Europe and North America only a few rare floors 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 or renter to select their preferred floor coverings, usually a wall-to-wall carpet or one-piece vinyl floor covering. Wood clad ([[hardwood]]) and tile covered finished floors generally 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 [[underfloor heating]] and if floor radiant heating is not used, will certainly suffer puncture openings to be put through for [[Duct (HVAC)|forced air duct]]s 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 exchanger]]s (radiators).

Some subfloors 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 molding and containing at least {{convert|2|in|cm|0|spell=in}} 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 ({{convert|4.5|in|cm|1|abbr=on|disp=or}} and smaller) ceramic tiles generally use only an additional {{convert|1/4|in|mm|1|adj=on}} 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 ===
{{Main|Solid ground floor}}

A ground-level floor can be an earthen floor made of [[soil]], or be [[solid ground floor]]s 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 meltwaters. Ground-level slab floors are prepared for pouring by [[grading (construction)|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 that is graded further so that it is flat and level, and then 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 [[reinforced concrete|reinforce the concrete]], and will be tied to the under slab "girder" rebar at intervals. The under slab cast girders are used especially if it the slab be used structurally, i.e., to support part of the building.

=== Upper floor construction ===
[[File:Katowice - new Central Station, construction 04.JPG|thumb|Multi-floor construction, [[Katowice]] (2012)]]
Floors in [[Framing (construction)|wood-frame homes]] are usually constructed with joists centered no more than {{convert|16|in|cm|0|abbr=off|sp=us}} apart, according to most [[building code]]s.{{Citation needed|date=June 2007}} Heavy floors, such as those made of [[Masonry|stone]], require more closely spaced joists. If the [[span (engineering)|span]] between load-bearing walls is too long for joists to safely support, then a heavy crossbeam (thick or [[laminate]]d wood, or a metal [[I-beam]] or [[H-beam]]) may be used. A "subfloor" of [[plywood]] or [[waferboard]] is then laid over the joists.

=== Utilities ===
{{Main|Building services engineering}}

In modern buildings, there are numerous services provided via ducts or wires underneath the floor or above the [[ceiling]]. The floor of one level typically also holds the ceiling of the level below (if any).

Services provided by subfloors include:

* [[Air conditioning]]
* [[Telecommunications]]
* [[Electrical wiring]]
* [[Compartmentalization (fire protection)|Fire protection]]
* [[Thermal insulation]]
* [[Plumbing]]
* [[sanitary sewer|Sewerage]]
* [[Soundproofing]]
* [[Underfloor heating]]

In floors supported by joists, [[Public utility|utilities]] are run through the floor by drilling small holes through the joists to serve as conduits.  Where the floor is over the basement or [[Basement#Crawl space|crawlspace]], utilities may instead be run under the joists, making the installation less expensive. Also, ducts for air conditioning (central heating and cooling) are large and cannot cross through joists or beams; thus, ducts are typically at or near the [[HVAC#Plenum space|plenum]], or come directly from underneath (or from an attic).

Pipes for plumbing, sewerage, underfloor heating, and other utilities may be laid directly in slab floors, typically via [[cellular floor raceways]]. However, later maintenance of these systems can be expensive, requiring the opening of concrete or other fixed structures. Electrically heated floors are available, and both kinds of systems can also be used in wood floors as well.
[[File:Mysore 1 22.jpg|250px|thumb|right|Floor tiles]]