What is furringin construction?

Furring, explained.

Furring strips create a secondary framing layer over an existing wall, masonry surface, or structural deck so finishes can be fastened plane and true. On a concrete or block wall, furring holds the gap that keeps drywall off the cold, damp masonry and gives room for a vapor barrier or rigid insulation. On a stud wall that has bowed or on rafters that are not coplanar, furring shims the surface back to flat. Wood furring is usually 1x2 or 1x3 nominal stock, while metal furring takes the form of hat channel or resilient channel, the latter chosen when sound isolation matters. Spacing follows the finish material: 16 in on center is standard for half-inch gypsum board, while wider spacing may suit thicker panels. Furring runs perpendicular to the joists or studs it crosses so each strip is fastened at every framing member. The estimator distinguishes furring from sleepers, which serve the same leveling role but lie flat on a floor slab to receive subfloor or finish flooring.