If we look at its definition in terms of carpentry, furring means to attach strips of wood or metal to a wall or other surface to provide an even surface for lath, or to provide air space between the wall and plasterwork. Wow, that's a mouthful. A bit easier way to explain it is that furring helps make surfaces even so the finished look has minimal imperfections.
Furring For Walls
If you've ever seen a bare wall, down to the wood-framing studs, it's easy to understand that it's not exactly the best surface to throw plaster or texture onto. Before any of those finishing touches go up, furring comes in.
Typically, the furring strips will be nailed perpendicularly to the studs in a horizontal fashion. Depending on the type of surface being applied, they're usually placed close together or a bit further apart-closer for materials like plaster, and further apart for materials like thin paneling or wire screening for stucco. This also helps to form an air pocket between the back of the wall and its surface.
It's important to know that with drywall, furring strips are very infrequently used against framing studs. Because drywall is so strong, it will normally be attached with screws directly into the wood studs. If the wood studs are uneven in places, however, thin strips of wood or paper, called shims, will be applied to even out the surface so the drywall doesn't bow in or out.
Furring As A Framing Technique
If you look at a bare area such as a basement before any walls go up, you'll find all kinds of things that challenge your designing eye. Drain pipes, air ducts, gas piping-how are you going to get around that? Furring is very often the answer.
The reason is simple. Standard 2x4s are often too bulky and/or too heavy to frame around challenging items like your ductwork. Since furring strips are commonly 1x2 inches in dimension, they provide a more compact, lightweight alternative that maintains great strength.
In these cases, furring strips are constructed as a sort of "ladder" that is fully bordered with several cross supports. Then, the furred ladders get attached to each other to box in whatever the obstruction may be. Once in place, they provide a very sturdy surface upon which to attach materials like drywall.
If you find yourself in need of some furring help, search Kudzu.com for professional carpenters, or browse our list of general contractors in your area.