Drywall thickness and where each is used
| Job | Used for |
|---|---|
| ¼ inch (6.4 mm) Bends around curves; laminated over old plaster or damaged walls | Curves, overlays |
| ⅜ inch (9.5 mm) Overlays and some remodel work; rarely used alone | Overlays |
| ½ inch (12.7 mm) The standard for interior walls. Lightweight versions available | Most walls |
| ½ inch ceiling board Sag-resistant, made for ceilings on wider framing spacing | Ceilings |
| ⅝ inch (15.9 mm), often Type X Stiffer, better sound control, fire-rated when Type X | Ceilings, suites, fire separations |
Walls: ½ inch
Half-inch (12.7 mm) drywall on studs spaced 16 inches apart is the default for interior walls. Drywall is still sold in imperial sizes in Canada, so a standard sheet is 4 feet by 8 feet and weighs roughly 50 pounds, about 23 kg; lightweight versions are noticeably lighter and easier to handle overhead.
Ceilings: ⅝ inch or sag-resistant ½ inch
Ceilings need stiffer board so it does not sag between joists over time, especially under the weight of insulation or a textured finish. Use ⅝-inch board, or ½-inch board labeled sag-resistant, and check the manufacturer's maximum framing spacing.
Garages and fire separation
The rules here differ from those in the United States. Under the BC Building Code, an attached garage that serves only one house does not need a fire-rated separation from the house. It does need a continuous air barrier that keeps exhaust fumes out of the living space, and the door between the garage and the house must be tight-fitting, weatherstripped and self-closing. Taped and finished drywall is normally part of that barrier, so a hole in a garage wall or ceiling next to the house should be patched and sealed, not left open.
Fire-rated Type X board is used where the code calls for a fire separation: between a house and a secondary suite, between units in duplexes, townhouses and condos, and around some service rooms. The rating required depends on the building, so replace like with like and ask your municipality before changing what is there.
Bathrooms, basements and showers
Moisture- and mould-resistant drywall comes in the usual thicknesses and suits bathroom walls, laundry rooms and basements. It is not waterproof. Inside a shower or tub surround, tile needs a cement board or a waterproofed backer instead.
Match the thickness when repairing
A patch must be the same thickness as the wall around it, or the repair sits proud or sunken and shows through paint. Check the thickness at an outlet box, where the edge of the board is visible after removing the cover plate, or measure the edge of the hole. Older homes may have ⅝-inch walls or plaster instead of drywall; see plaster wall repair. For methods, see how to fix a hole in drywall, and for prices, drywall installation cost.
Common questions
What thickness is standard drywall?
Half an inch, or 12.7 mm, for interior walls in most homes. Ceilings and fire-rated areas often use ⅝ inch, or 15.9 mm.
Is ⅝ drywall better than ½?
It is stiffer, blocks more sound and, as Type X, is fire-rated. It is also heavier and costs more, so it is used where those benefits are needed rather than everywhere.
Can I put ½-inch drywall on a ceiling?
Yes, if it is sag-resistant ceiling board and the joists are within the spacing the manufacturer allows. Regular ½-inch wall board is more likely to sag on ceilings.
What drywall goes between a house and a basement suite?
The wall and ceiling between a house and a secondary suite is a fire separation, and it is usually built with Type X board. The exact requirement depends on the building and when it was built, so match the existing board in a repair and check with your municipality for new work.
Related guides
Based on manufacturer guidance and the BC Building Code (Part 9); municipal requirements vary. We update these figures as we complete jobs.