How much drywall for a stairwell?

For a 9 ft floor-to-floor stair with 10 in treads, walls on both sides 7.5 ft above the nosing, an end wall and a sloped ceiling, the calculator above gives the area and sheets. Change the inputs to match your stair.

Stairwell Drywall Calculator

Enter the floor-to-floor height and the treads. The calculator works out the stair from the IRC limits, then the rake walls, the end wall and a sloped ceiling, and the sheet length that spans the flight.

Rake wall area
IRC stair limits
Sheet length picker
Sloped ceiling

By Inam Ur Rehman · Updated October 2026

Your estimate

14 risers of 7.71 in, 15% waste for angled cuts

6sheets of 4' x 14'
long enough for the slope

The flight

Horizontal run10 ft 10 in13 treads

Length along the slope14 ft 1 ina 4' x 14' sheet spans it

Area

Side walls163 sq ft

End wall58 sq ft

Sloped ceiling49 sq ft

Total270 sq ft

Sheets of 4x8 instead10more joints on the rake

Risers are the floor-to-floor height divided into steps no taller than the IRC's 7-3/4 in. Each side wall is a parallelogram over the flight, so its area is the run times the plumb wall height above the nosing line.

The walls beside a stair are the awkward part of any drywall job: they are taller than a room, cut on an angle, and too high to reach from the stairs themselves. The board follows the flight, so each side wall is a parallelogram, as tall above the nosing line as the headroom, and as long as the stair's horizontal run. The calculator finds the run from the floor-to-floor height using the code's limits on riser height and tread depth, then works out each surface.

From floor height to wall area

Risers = floor-to-floor height divided into steps no taller than 7-3/4 in, the maximum in 2024 IRC R318.7.5.1 (R311.7.5.1 in 2021), rounded up. One flight may rise no more than 12 ft 7 in.
Run = one fewer tread than risers, times the tread depth (10 in minimum under the IRC).
Side wall = run x the plumb height of wall above the nosing line. The IRC requires at least 6 ft 8 in of headroom there.
End wall = stair width x the full height from the lower floor to the upper ceiling.
Sloped ceiling = stair width x the length along the slope of the flight.

Choosing sheet length for a stairwell

A rake wall finishes best with the fewest joints, and joints on a stairwell are hard to reach. The calculator suggests the shortest stocked sheet that spans the slope of the flight in one piece: often 12 ft for a single-story stair, 14 ft for a tall one. Check you can get it up the stairs before you buy it.

The waste allowance is 15% here rather than 10%, our estimate for the angled cuts along the stringer and the ceiling line.

The space under the stair

If the space under the stair is enclosed and has a door or access panel, IRC R302.7 requires its walls, the underside of the stair and any soffits to be protected on the enclosed side with 1/2 in gypsum board. Turn on the under-stair option in the calculator to include the stringer triangle, and board the sloped underside as well.

Working above a stair

Use a stair platform or a ladder with leg levelers, or scaffold planks bridged from the stair to a landing. Never stand a ladder on a tread and lean it on fresh board.

Frequently asked questions

Hang the end wall and the sloped ceiling first, then the rake walls in long sheets laid along the flight, cutting the bottom edge to follow the stringer. Use the longest sheet that spans the slope so you tape as few joints as possible from a ladder.

Primary references

Manufacturer and industry guidance used to check this article.

Product instructions, tested assemblies and local code take priority over general guidance.