How to work out how many sheets you need
Start with the area you are covering: all four walls, plus the ceiling if it is part of the job. Subtract large openings such as windows and doors, add a waste factor, then divide by the area of one sheet. A 4 by 8 foot sheet covers 32 square feet. A 14 by 12 foot room with 8 foot walls and a ceiling comes to 416 square feet of wall plus 168 of ceiling, less about 35 for openings, so 549 square feet. With 10 percent waste, that is 604 square feet, or 19 sheets.
Which sheet size should you buy?
Longer sheets mean fewer seams. A 4 by 12 sheet can run the entire length of a typical room wall with no butt joint, and butt joints are the hardest seams to hide. The trade-off is weight and handling: a 4 by 12 sheet of half inch board weighs about 80 pounds and is awkward to carry up a staircase. Most DIYers do better with 4 by 8, and ceilings are often easier with 4 by 12 and a helper or a lift.
Thickness and type matter in Canada
Half inch (12.7 mm) board is the common choice for walls and ceilings framed 16 inches on centre. Five-eighths inch (15.9 mm) board is stiffer, hangs flatter on ceilings and is what many fire-rated assemblies call for. Type X board, with a fire-resistant core, is typically required on the wall and ceiling between an attached garage and the house, and in some multi-unit buildings. Green or purple moisture-resistant board is meant for bathrooms and laundry rooms. Because requirements differ across provinces and municipalities, confirm yours with the building department before you buy.
Tape, screws and compound
The extra materials follow the area. Plan on roughly 0.37 linear feet of tape per square foot, around one screw per square foot at standard spacing, and about 17 litres of premixed all-purpose compound per 450 square feet for taping, topping and skim coats. These are guidelines and will vary with your technique. Quantities in the calculator give you a starting point so you do not run out midway through a coat.
Waste and cutouts
Ten percent is a normal waste factor for a simple rectangle. A room with many windows, angled walls or cuts for stairwells may need 15 percent. Keep your offcuts, since smaller pieces fit above doors and under windows. If you want to be precise, make a sketch of each wall with the sheet layout, and count sheets directly.
Hanging and finishing basics
Hang the ceiling first, then the walls, and run sheets horizontally where you can so that seams fall at a comfortable height. Stagger butt joints, keep screws about 12 mm from edges, and dimple them just below the surface without breaking the paper. Finishing takes three coats of compound with drying time between, plus sanding. Do not rush the drying in a cold basement, and keep the room at least 10 degrees Celsius.
After drywall comes paint
Once the surface is smooth, prime it with a drywall primer. Use our paint calculator to work out how much paint and primer to buy for the same room.
Frequently asked questions
How many sheets of drywall do I need for a room?
Divide the total wall and ceiling area, plus about 10 percent waste, by the area of one sheet. A 4 by 8 sheet covers 32 square feet.
How many 4x8 sheets of drywall for a 12x12 room?
A 12 by 12 room with 8 foot walls and a ceiling is about 432 square feet before openings, which is roughly 15 sheets with waste.
What thickness of drywall should I use?
Half inch is standard for walls and ceilings. Use 5/8 inch where fire rating, stiffness or sound control is needed.
How much joint compound do I need?
Around 17 litres of premixed compound per 450 square feet of drywall for a standard three-coat finish.
Do I need fire-rated drywall in my garage?
Typically the wall and ceiling between an attached garage and the house need a fire-rated or Type X assembly. Check your provincial code and local building department.
Should drywall go horizontal or vertical?
Horizontal is usually preferred on walls because it reduces butt joints and makes seams easier to finish.
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