An arched opening or a curved stair wall looks simple when it's finished. Getting there takes framing that holds the curve, board that bends without cracking, a corner that follows the line, and a finish that survives the light.
The curve starts in the framing
The shape is set before any board goes up. On steel framing the track is cut along its flange so it can bend to the radius, and the studs go closer together than on a straight wall, so the board has support all the way round. A wave in the framing will show in the finished wall, so this is where the curve is checked.
Board made to bend
Ordinary half-inch board won't take a tight curve. USG makes a quarter-inch flexible gypsum panel for curved walls, archways and stairways, more flexible than its standard quarter-inch board. Fine Homebuilding notes it is usually hung in two layers with the seams staggered, and that for short radii, 32 inches or less, the board may need wetting with a sponge or roller before it is fastened so it bends instead of cracking.
A corner that follows the arch
The outside edge of an arch needs a corner bead that bends with it. Trim-Tex makes flexible vinyl archway beads for this, notched along their legs so they follow the curve of the opening. Set true, the bead gives the arch its clean line and protects the edge.
The finish has to hold up in side light
Curves catch light at a low angle, the way a lamp across a wall shows every ridge. The Gypsum Association's levels of finish call this critical lighting, and recommend a Level 5 finish, a thin skim coat over the whole surface, where it occurs on smooth walls. A curved wall beside a stair window or under a skylight is a fair case for it.
Before you plan one
- Decide the radius and the opening height early, with the framer and the finisher in the same conversation.
- Say whether the wall will be smooth or textured, and what paint goes on it: it sets the level of finish.
- Look at the wall under the light it will have, before paint, while there is still time to fix a wave.
Sources
- Sheetrock Brand Flexible Gypsum Panels USG.
- Flexible and other specialty drywall Fine Homebuilding.
- How to finish around archways like a pro Trim-Tex.
- Discover five levels of gypsum board finish National Gypsum.
