What is strapping, when to use it, spacing calculations, and best practices
Strapping (also called furring or furring strips) refers to strips of wood or metal installed perpendicular to joists, studs, or existing surfaces to create a level base for attaching finish materials.
Strapping creates an air gap and provides a consistent nailing or fastening surface. It's commonly used in ceiling and wall applications to correct irregularities, improve insulation, and facilitate the installation of drywall, paneling, or siding.
| Material | Common Sizes | Best Use | Notes |
|---|---|---|---|
| Wood Strapping | 1×3, 1×4, 2×2, 2×3 | Ceilings, walls, general purpose | Most common. Use SPF or pressure-treated for concrete/masonry. |
| Metal Hat Channel | 7/8", 1-1/2", 2" | Ceilings, resilient sound isolation | Provides sound dampening. Lightweight and rust-resistant. |
| Z-Channel | 1", 1-1/2" | Walls, exterior foam insulation | Creates drainage gap. Good for rainscreen systems. |
| Resilient Channel | 1/2", 5/8" | Soundproofing ceilings and walls | Decouples drywall from framing to reduce sound transmission. |
| Plywood Strips | 3/4" × 1-1/2" strips | Heavy-duty applications, leveling | More stable than 1× lumber. Use for shimming large areas. |
| Application | Typical Spacing | Notes |
|---|---|---|
| Ceiling Drywall (1/2") | 16" O.C. | Prevents sagging. Maximum for 1/2" drywall. |
| Ceiling Drywall (5/8") | 24" O.C. | Thicker drywall can span further. Still use 16" O.C. for best results. |
| Wall Drywall | 16" or 24" O.C. | Follow existing stud spacing. 16" O.C. is standard. |
| Wood Paneling | 16" O.C. | Depends on panel thickness. Check manufacturer specs. |
| Exterior Siding | 16" or 24" O.C. | Follow siding manufacturer recommendations. Match stud locations if possible. |
| Rainscreen/Vertical Strapping | 16" O.C. | Must hit studs behind sheathing. Use longer fasteners. |
| Metal Hat Channel | 24" O.C. | Typically used with 5/8" Type X drywall for fire rating. |
Formula:
Example: For a 12-foot ceiling with 16" O.C. spacing:
Always start with a strip at one edge and end with a strip at the opposite edge for proper support.
Determine why you need strapping and measure the space. Check for level/plumb and identify high/low areas. Calculate spacing and materials needed.
Snap chalk lines perpendicular to joists/studs at your chosen spacing (typically 16" O.C.). Use a laser level or string line to ensure lines are straight and level.
Start at one edge of the room. Fasten the first strapping strip, shimming as needed to achieve level. This becomes your reference for all other strips.
Place a straightedge or laser across joists. Add shims under strapping at low areas. Tap down high areas or add shims to adjacent areas to create a flat plane.
Continue installing strapping at marked intervals. Fasten at every joist or stud crossing. Maintain consistent spacing using a measuring tape or spacer block.
Use a long straightedge to check for consistent plane across all strapping. Verify spacing with a tape measure. Make final adjustments before proceeding.
Hang drywall, paneling, or siding perpendicular to strapping direction. Fasteners should penetrate strapping and into structural members behind for maximum holding power.
Note: Building codes vary by location. Always check with your local building department before beginning work, especially for basement strapping, fire-rated assemblies, and exterior applications.
Disclaimer: This guide provides general information about strapping installation. Local building codes, climate conditions, and project-specific factors may require different approaches. Always consult with a licensed contractor or building inspector for your specific application and verify compliance with local codes before beginning work.