Blocking in Construction: What It Is and Why It's Added During Framing

Blocking refers to pieces of lumber installed between studs, joists, or rafters to provide solid backing for mounting hardware, fixtures, and structural elements. Blocking provides a nailing or screwing surface where no stud exists at the needed location.

Blocking is most effectively added during the framing phase of a remodel, before walls are drywalled, because installing it after walls are closed requires cutting into finished surfaces to access the framing cavity. Adding blocking during an open-wall remodel at negligible additional cost is one of the most practical forms of future-proofing a home.

At Phoenix Home Remodeling, blocking locations are identified during the design phase and coordinated with our framing subcontractor. Bathroom blocking for grab bars, shower glass hardware, wall-mount fixtures, and towel bar backing is standard in every bathroom remodel we complete.

Because the cost of adding blocking during an open-wall remodel is essentially zero. The walls are already open, the framer is already on-site, and the lumber cost is minimal. Adding blocking after walls are drywalled and painted requires cutting access holes, installing lumber, patching drywall, retexturing, and repainting. A towel bar that required thirty minutes and two dollars of lumber during framing can cost five hundred dollars or more to retrofit correctly after the fact.

• Grab bars: ADA-compliant grab bars must support 250 pounds of force and must be anchored into solid blocking or structural framing. Blocking for grab bars in all shower and tub areas should be standard in every bathroom remodel, regardless of whether grab bars are being installed now.

• Shower glass hardware: Frameless glass enclosure hardware anchors must attach to solid backing. Wall bracket locations for hinges and mounts must have blocking behind the tile. This must be installed during framing, before waterproofing and tile.

• Towel bars and accessories: Towel bars, toilet paper holders, and robe hooks that carry daily load should be anchored into blocking. Surface-mounted anchors in drywall only fail with regular use over time.

• Wall-mount fixtures and vanities: Wall-hung toilets and floating vanities attach directly to the wall and carry significant weight. Blocking or reinforced backing plates must be installed at attachment points during framing to support these loads safely.

• TV and speaker mounts: In primary bathrooms or media rooms where TVs are wall-mounted, blocking at the intended location eliminates the need to hunt for studs and allows placement at the optimal height regardless of stud spacing.

For very light loads like small picture frames, drywall anchors are acceptable. For anything carrying daily dynamic loads, such as towel bars, grab bars, or TV mounts, drywall anchors are not an adequate substitute for solid backing. The failure mode is not dramatic, it is gradual pull-out that loosens the mount over time until one day the fixture comes out of the wall.

The ADA specifies 33 to 36 inches above the finished floor for horizontal grab bars in shower and tub applications. Installing a continuous horizontal blocking band at 32 to 48 inches height covers the full range of possible grab bar positions and allows the grab bar to be set at exactly the right height for the user rather than being constrained by framing.

We identify blocking locations during our design phase for every bathroom remodel. Grab bar blocking, shower glass hardware backing, and accessory backing are standard inclusions in our bathroom scopes. Our framing subcontractor installs specified blocking before waterproofing and tile begin. We document blocking locations on our as-built notes so future accessory additions can be made without guesswork.

• Are you installing grab bar blocking in shower and tub areas?
• Where is the backing for frameless shower glass hardware being located?
• Is there blocking at towel bar and accessory locations?
• If we are installing a wall-mount vanity or toilet, is the backing sized adequately?
• Can we add a blocking band at 32 to 48 inches throughout the shower to future-proof for grab bars?

See also: Frameless Shower Glass, ADA Bathroom Requirements, Aging-in-Place Design, Walk-In Shower Design, Load-Bearing Wall, Construction Sequencing