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How Many Sheets of Drywall Do I Need? Measuring a Room and a House, 8-ft vs 12-ft Board, Waste, and Why the Boarder Orders More
Drywall, Taping & Painting
How Many Sheets of Drywall? The Math for a Room, the Math for a House, and the Reason the Order Is Always Bigger Than the Math
Dividing the square footage by 32 gets you a number. It is the wrong number, in a way that matters: it assumes every offcut gets used, every wall is a multiple of 4 ft, and nobody breaks a corner off a sheet carrying it in. A boarder orders by wall, choosing the sheet length that puts the fewest joints in the room, and then adds about 10%. Here is how to do it his way so the yard delivers once.
The sheet sizes and what they are for
| Sheet | Area | Weight, 1/2 in. | Use it for |
|---|---|---|---|
| 4 x 8 | 32 sq ft | about 51 lb | 8-ft walls stood vertical, small rooms, repairs, anything you carry down a basement stair yourself. |
| 4 x 9 | 36 sq ft | about 58 lb | 9-ft walls stood vertical with no horizontal joint. Not every yard stocks it. |
| 4 x 10 | 40 sq ft | about 64 lb | Walls up to 10 ft long run horizontally, and ceilings in rooms under 10 ft wide. |
| 4 x 12 | 48 sq ft | about 77 lb | What the trade uses. Run horizontally on walls, one joint at 4 ft off the floor, butt joints only where the wall is longer than 12 ft. Ceilings across the joists. |
| 54 in. x 12 | 54 sq ft | about 86 lb | Two courses cover a 9-ft wall with one horizontal joint and no filler strip. The 9-ft-ceiling sheet. |
Longer sheets mean fewer butt joints, which are the joints that show, because a butt joint has no tapered edge and the taper has to build a hump to hide it. The whole point of the order is to minimise them.
The room
Take the 12 by 12 bedroom with an 8-ft ceiling. Perimeter 48 ft, gross walls 384 sq ft, one door and one window off, about 350 net. Ceiling 144. Total 494 sq ft. Divide by 32 and you get 15.4 sheets of 4×8.
Now do it the boarder’s way. Four walls, each 12 ft long and 8 ft high: one 4×12 sheet laid horizontally on the top half, one on the bottom, four walls, eight sheets, one horizontal joint per wall and no butt joints at all. The ceiling: three 4×12 sheets across the joists. Eleven sheets of 4×12, 528 sq ft, and the offcuts from the door and window are what you lose. He does not deduct the openings, because the board that was there is in the dumpster, not on another wall.
The rule: measure each wall, pick the sheet length that covers it with the fewest butt joints, count whole sheets, do not deduct openings under about 30 sq ft, then add 10% for breakage and mistakes. For the house, do it room by room or use the floor-area shortcut below and let the boarder fix it.
The house
A 2,000 sq ft house with 9-ft ceilings on the main floor and 8-ft upstairs has around 6,500 sq ft of drywall surface. That is 225 sheets of 4×8, or about 150 of 4×12 with waste, which is a lift and a half on a boom truck. A 1,400 sq ft bungalow with 9-ft ceilings is about 4,800 sq ft and 110 sheets of 4×12. A 1,000 sq ft basement is 3,400 sq ft and 80 sheets, with more waste because of the bulkheads.
Alongside the board, per 1,000 sq ft of surface: about 1 lb of screws per 100 sq ft, so 10 lb; a 20-kg box of all-purpose compound covers roughly 400 sq ft through three coats, so two and a half boxes; a 500-ft roll of paper tape does about 1,000 sq ft; corner bead by the count, 8-ft lengths. The drywall calculator counts sheets both ways for your rooms.
Where homeowners go wrong
- Buying 4×8 for a 9-ft wall. Two sheets stood vertically leave a 1-ft strip to fill and a joint every 4 ft. Buy 54-in. board or 4×12 run horizontally.
- Deducting every window. The board you cut out of a 36-in. opening is scrap. Deduct only openings big enough to save a whole sheet, like a patio door or an archway.
- Ordering exactly the count. One sheet breaks coming off the truck and one gets cut wrong. Ten percent is normal; the yard takes back unopened full sheets, usually.
- Hand-carrying 12-footers down a basement stair with a landing. They do not turn the corner. Basements get 4×8 or 4×10, or the board goes in through a window well before the window does.
- Forgetting the ceiling board is different. Ceilings on 24-in. trusses need 5/8 or sag-resistant 1/2 in. ceiling board, ordered separately. Ceilings.
Questions people ask
How many sheets of drywall for a 12×12 room?
About 15 sheets of 4×8 by the area, or 11 of 4×12 laid out properly, for walls and ceiling with an 8-ft ceiling. Order 12 of the 4×12 and bring the spare back.
How many sheets of drywall for a 1,000 sq ft basement?
About 3,400 sq ft of surface with the bulkheads, so 115 sheets of 4×8 or 80 of 4×10, plus 10%. Basements waste more because every bulkhead is small pieces.
Should drywall be hung vertically or horizontally?
Horizontally on walls in a house: the joint lands at 4 ft where it is easy to finish, the sheet bridges more studs so the wall is stiffer, and a 12-ft sheet gives you a 12-ft wall with no butt joint. Vertical is for walls under 8 ft long and for commercial fire-rated assemblies that call for it.
Does the yard deliver drywall into the house?
With a boom truck, yes, through a window or door opening, stocked in the rooms you tell them. About $350 for a house. Curbside delivery is cheaper and then it is you and a friend and 150 sheets.
Let the calculator count it
The drywall installation calculator takes your rooms and gives you the area, the 4×8 and 4×12 counts with waste, and the installed price. The cost guide explains the rates.
Sources and further reading
- CGC Inc.: the maker of most of the board and compound in Ontario; the product sheets give thicknesses, span limits for ceilings and the right compound for each coat.
- CertainTeed Gypsum Canada: the other common board in Ontario yards; their installation guides and Level 5 primer-surfacer data are on the site.
- Gypsum Association construction standards: GA-216 application and finishing (the hanger’s bible: fastener spacing, ceiling framing limits, joint treatment) and GA-600 fire resistance design manual, with the free downloads.
