How the sheets are counted
- Wall area is the room's distance around times the ceiling height. A 14 by 12 foot room with 8 foot ceilings has 2 × (14 + 12) × 8 = 416 sq ft of wall.
- Doors and windows come off at 20 sq ft a door (3' by 6' 8") and 15 sq ft a window (3' by 5'). Hangers often run sheets over small openings and cut them out, which the waste covers.
- The ceiling is the room's length times its width: 14 × 12 = 168 sq ft.
- Sheets are the area plus waste divided by one sheet: 32 sq ft for 4' by 8', 40 for 4' by 10' and 48 for 4' by 12'. Walls and ceiling are counted apart and each rounded up, since ceilings are often a different board.
- Tape and compound follow USG's published coverage: about 370 feet of paper tape and two 4.5 gallon pails of ready-mixed all-purpose compound for every 1,000 sq ft of board.
Choosing the sheet size
Hung across the studs, two rows of 4 foot sheets fill an 8 foot wall, and 4' by 8' sheets are the easiest to carry in and lift. Longer 4' by 10' and 4' by 12' sheets span more of a wall in one piece, so there are fewer butt joints to tape, but they are heavier and harder to get through doors and up stairs. Rooms with 9 or 10 foot ceilings pair well with 4' by 9' or 4' by 10' sheets stood on end.
Thickness
- 1/2 inch is the standard board for walls and ceilings in houses.
- 5/8 inch is stiffer, so it is common on ceilings to limit sag. In its fire-rated Type X form the code calls for it in places such as a garage ceiling under living space (IRC Table R302.6).
- 1/4 and 3/8 inch bend around curves and cover old walls and ceilings.
- Moisture-resistant board goes in bathrooms and laundry rooms; behind tile in showers, cement board or a tile backer is used instead.
Common questions
How many sheets of drywall does a 12 by 12 room take?
With 8 foot ceilings, one door, two windows and 10% waste: 12 sheets of 4' by 8' for the walls and 5 for the ceiling, 17 in all.
How much area does one sheet cover?
A 4' by 8' sheet covers 32 sq ft, a 4' by 10' sheet 40 sq ft and a 4' by 12' sheet 48 sq ft.
How much tape and mud does a room need?
About 370 feet of tape and 9 gallons of ready-mixed all-purpose compound to tape and finish 1,000 sq ft of board. Lightweight and setting compounds cover differently; the bag or pail gives the figure.
How much waste should be added?
About 10% for a plain room hung in long sheets, and 15% for rooms with many openings, angles or short walls, where more of each sheet is cut off.
Does the count include corner bead?
No. Outside corners take corner bead, ordered by the length of each corner, usually in 8 and 10 foot pieces.