How to Choose the Right Drywall Thickness for Your Project

Drywall isn't one-size-fits-all. Walk into any building supply in the GTA and you'll find panels ranging from 1/4 inch to 5/8 inch — and picking the wrong one can mean a failed inspection, poor acoustics or a surface that doesn't hold up. Here's how to make the right call every time.

The Four Standard Thicknesses

Thickness	Best Use	Notes
1/4"	Curves, repairs, over existing surfaces	Flexible, not structural
3/8"	Patches and light partitions	Less common; lighter than 1/2"
1/2"	Standard walls and ceilings	The go-to for most residential projects
5/8"	Fire-rated assemblies, ceilings with wide spans	Required by Ontario Building Code in certain applications

1/2 Inch: The Standard Choice

For most residential walls in Toronto homes, 1/2 inch drywall is the right call. It's rigid enough to resist dents, light enough to work with efficiently and widely available at every supplier in the GTA. Unless a specific code requirement or application demands otherwise, 1/2 inch is where you start.

On ceilings, the same applies — with one caveat. If your framing is spaced at 16 inches on centre, 1/2 inch works. At 24 inches on centre, you're better off with 5/8 inch to prevent sag over time.

5/8 Inch: When Code Requires It

Ontario's Building Code mandates fire-rated assemblies in specific locations — party walls between units, garage-to-living-space separations and certain commercial partitions. In those cases, 5/8 inch Type X drywall is the minimum. It contains glass fibres that slow the spread of fire, buying the time the code is designed to protect.

If you're working on a multi-unit residential build or a commercial tenant fit-out, assume 5/8 inch Type X anywhere there's a fire separation requirement. Get it wrong and you'll be tearing it out before the inspection.

Moisture-Resistant Panels

Thickness is only part of the equation in wet areas. Bathrooms, kitchens behind backsplashes and laundry rooms need moisture-resistant board — commonly called greenboard or blueboard — regardless of thickness. Standard 1/2 inch moisture-resistant drywall handles most bathroom applications; tile backer board (cement board) is the right call anywhere tile is going directly over the surface.

1/4 Inch: Specific Uses Only

Quarter-inch drywall is flexible enough to wrap around curved walls and arches. It's also useful for doubling up over existing surfaces when you want to add mass without tearing down. Outside of those situations, it's too thin for a primary surface — it dents easily and doesn't hold fasteners the way thicker panels do.

What This Means for Your Budget

Thicker panels cost more per sheet and are heavier to handle, which affects labour time. 5/8 inch takes longer to cut, hang and finish than 1/2 inch. For large projects, over-specifying thickness where it isn't required adds cost without adding value. The right spec is the one the job actually needs — not the heaviest panel available.