Furring

In light-frame construction, furring strips are long thin strips of wood or metal used to make backing surfaces to support the finished surfaces in a room. Furring refers to the backing surface, the process of installing it, and may also refer to the strips themselves.

Furring strips typically measure 1" x 2" or 1" x 3". They can be laid out perpendicular to studs or joists and nailed to them, or set vertically against an existing wall surface. The spacing between the strips depends on the type of finishing material. Wider spacing is typically used behind the heavy boards that support ceramic tiles. Closely spaced strips are needed for thin panelling or plaster. The use of strips with plaster, however, is called either lath and plaster or wattle and daub.

Metal furring strips can be used in towns where fire-proof supporting elements are required by the local building code. Often called "hat channels" to describe the profile (cross section), two flanges on each side of trapezoid shape, with a dimension of 7/8^th of an inch thickness.

Furring is also used to support roof materials and may be seen under barn and shed roofs, but is often replaced in contemporary times by labor-saving plywood. Drywall has become the most common interior wall finishing material and doesn't need furring due to its strength. Furring is still used in remodeling work to fill out uneven sections for resurfacing, or to add room for insulation.

"Firring" is a U.K. term for wood strips which are usually 50mm wide, tapered and fixed above wood roof joists to provide drainage falls below roof boarding.

Furring strips themselves are typically referred to as "battens" in the U.K..

Another, more erudite guess at the derivation is the German word Führung, meaning guiding or leading, which is the function of these strips. wood or metal