A furring strip is a narrow piece of material, typically wood or thin-gauge metal, used in construction and remodeling projects. These strips are generally applied to an existing wall, ceiling, or floor structure before the final surface material is installed. The primary function is to establish a flat, plumb, or level plane over an uneven substrate, or to create a deliberate air gap between layers of material. This practice allows builders to securely attach new finishes like drywall or paneling even when the underlying structure is irregular.
Defining Furring Strips
Furring strips most commonly appear as rough-sawn lumber, often nominally measuring 1 inch by 2 inches, though their actual dimensions are usually closer to $3/4$ inch thick by $1-1/2$ inches wide. These simple wood strips are often made from inexpensive softwoods and do not require the high-quality finish or strict dimensional tolerances found in framing lumber. The term “furring” refers to the process of building out a surface to make it level or to add space.
Beyond wood, metal furring channels are frequently used, particularly in commercial construction or areas requiring enhanced fire resistance. These channels, often called “hat channels” due to their cross-sectional shape, are typically thin-gauge galvanized steel. Hat channels are preferred when fastening to steel framing or concrete, offering a non-combustible attachment base for drywall panels. Their standardized shape ensures a consistent depth, which helps maintain a uniform distance from the original structure.
Primary Uses and Applications
One of the most frequent uses for furring strips is correcting irregularities in an existing structural surface, such as an aged plaster wall or an uneven ceiling joist system. By shimming or adjusting the thickness of the strips before they are secured, a contractor can establish a perfectly flat plane, or a “true” surface, for the subsequent installation of new material. This process ensures that new drywall or paneling sits flush and avoids the visible waves and dips that would otherwise mirror the underlying imperfections.
Furring strips are also regularly employed to create an air space or drainage plane, especially when finishing basement walls or exterior masonry. When applied to concrete or brick, the strips hold the new wall finish away from the damp substrate, preventing moisture transfer and allowing condensation or water intrusion to drain or evaporate. This intentional gap interrupts the thermal bridge between the cold exterior wall and the interior finish, which helps mitigate the risk of mold and mildew growth behind the panels.
Furring strips provide a suitable nailing base over substrates that cannot accept traditional fasteners, such as solid concrete walls or steel framing members. Concrete, for example, is too dense and brittle for directly nailing finishing materials. Applying wood furring strips to the concrete first creates a continuous, secure strip of material for the finishing panels to be fastened into. This technique is commonly used when attaching insulation boards or paneling directly over a concrete slab or block foundation.
Installation Considerations
Proper layout is a key step when installing furring strips, as the spacing must align with the finishing material being applied. For standard drywall or wood paneling, strips are typically installed either 16 inches or 24 inches on center, corresponding to the common widths of these finishing products. This measured spacing ensures that the edges and the center of the panels have adequate backing for secure attachment.
The method for securing the strips depends entirely on the nature of the underlying substrate. When fastening to masonry, specialized hardened steel masonry nails or concrete screws, such as tapcons, are used to penetrate the material. Conversely, when attaching to a steel structure, self-tapping metal screws are the preferred fastener to ensure a strong mechanical bond. In certain non-structural applications, construction-grade adhesives may be used in conjunction with mechanical fasteners to provide stability and reduce movement.