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Fire-Rated Drywall in Ontario: Type X, the Garage Separation, Furnace Rooms, Basement Apartments and What a “Rating” Actually Is
Drywall, Taping & Painting
Fire-Rated Drywall in Ontario: Where Type X Goes, What a Rating Really Is, and Why a Thicker Sheet on One Side of a Wall Is Not One
Type X is gypsum board with glass fibres in the core so it holds together longer in a fire. It costs about $0.30 a square foot more than regular board and it is required in a handful of places in a house, most of them between the garage and the rooms you sleep in. The thing to understand is that a fire rating is a tested wall or ceiling, not a product. Type X screwed to one side of a stud wall with nothing on the other is a thicker unrated wall. Here is where the Ontario Building Code wants rated assemblies in a house, and what they look like.
Where it is required, or wanted, in a house
| Location | What the code is after | What gets built |
|---|---|---|
| Attached garage, wall to the house | A gas-tight separation so exhaust and gasoline vapour stay in the garage, and in many cases a fire-resistance rating | 5/8 Type X taped and sealed on the garage side, or 1/2 in. taped both sides where only the air barrier is required. Every joint, every penetration, every box sealed. The door into the house is a tight-fitting, self-closing, weatherstripped door. |
| Garage ceiling under a bedroom or living space | The same separation, overhead, where a fire would go first | 5/8 Type X, screws at 12 in., joints taped, all penetrations fire-stopped. Most Ontario inspectors want this regardless of how the clause is read. |
| Furnace or mechanical room | Depends on the appliance and the plans; often nothing extra for a modern sealed-combustion furnace | If the drawings show a rated room, Type X both sides and a rated door. Ask the designer; do not guess. |
| Basement apartment or secondary suite | A fire separation between the units, usually 45 minutes in Part 9, and between the suite and shared spaces | Rated floor-ceiling assembly: 5/8 Type X on resilient channel or on the ceiling joists per a listed assembly, rated walls, rated doors, interconnected smoke alarms. Legalizing a basement apartment. |
| Under stairs, around chases | Containing fire in concealed spaces | Board under the stairs and fire-blocking in chases, per the drawings. |
| Everywhere else | Flame-spread limits on the interior finish, which drywall meets easily | Regular board. |
The exact clauses move between code editions and municipalities read them differently. The reliable approach is to ask your building inspector at the framing inspection what they want to see on the garage walls and ceiling, and write it on the drawings.
What a rating is
A 45-minute or 1-hour rating belongs to an assembly: a particular board thickness on a particular framing, fastened a particular way, with a particular thing on the other side, tested as a whole. The Gypsum Association’s GA-600 Fire Resistance Design Manual and the manufacturers’ listings are the catalogues of those assemblies. A standard one-hour wall is 5/8 Type X on both sides of wood studs at 16 in., screws at 8 in. on the perimeter, joints taped. Change the screw spacing or leave the other side bare and you no longer have the tested wall.
This is why “I put 5/8 on the garage” is not an answer to the inspector. The question is which assembly, and whether the joints, the penetrations and the door match it. Taping matters: a rated wall needs its joints taped and fastener heads covered even in a garage where nobody cares how it looks. That is Level 1 or Level 2 in the finishing standard, sometimes called fire taping. The levels.
What it costs
Type X 5/8 is $0.30 a square foot more than regular 1/2 in., hung. A typical attached two-car garage has about 900 sq ft of wall and ceiling against the house, so $270 in board and maybe $400 all in with the sealing and the fire-stopping of penetrations. The heavier board slows the hanging on the ceiling. A rated basement-suite ceiling with resilient channel and sound insulation is a different job and the soundproofing page covers it, because the rated assemblies and the quiet assemblies are mostly the same ones.
Where homeowners go wrong
- Leaving the garage untaped because it is a garage. The separation is the joints. Untaped Type X is a row of 1/8-in. gaps.
- Cutting a hole for the dryer vent or the panel and leaving it. Every penetration through the separation gets fire-stopped. The inspector looks at exactly these.
- A hollow-core door into the garage. It has to be tight-fitting and self-closing, and most inspectors want a solid or rated slab. The $60 door is a failed inspection.
- Finishing a basement apartment with regular board on the ceiling. The separation between units is the whole legal point of the suite. Basement apartment costs, and for a detached suite in the yard, where the same separation rules apply between the suite and a garage, GardenSuiteOntario.com.
- Buying “fire-resistant” instead of Type X. All gypsum board resists fire; Type X is the listed product with the core that holds. Check the stamp on the back of the sheet.
Questions people ask
Is 5/8 Type X drywall required in a garage in Ontario?
On the ceiling under living space, nearly every Ontario inspector wants it, and on the walls to the house many do; the code clause asks for a gas-tight separation and a rating where the garage is under or beside sleeping areas depending on how it is read. Ask your building department before the board goes up, and tape and seal everything either way.
Does Type X drywall need to be taped?
Yes, in any rated or separating assembly. The joints and the screw heads get at least a tape coat (Level 1 or 2) even where nobody will see it, because an untaped joint is a gap and a gap is not a separation.
How much does fire-rated drywall cost?
About $27 a 4×8 sheet at the yard against $21 for regular 1/2 in., and about $0.30 a square foot more installed. The sealing of penetrations and the rated door cost more than the board does.
What is the difference between Type X and Type C?
Type C has more glass fibre and an additive that keeps it from shrinking as it dehydrates; it is used in ceiling assemblies and in some one-hour walls where the listing names it. If a listed assembly says Type C, Type X is not a substitute.
Budget the garage with the house
The drywall installation calculator has a Type X line for the garage and furnace room so the whole house is one number. The before-drywall checklist covers what the inspector looks at before any of it goes up.
Sources and further reading
- Ontario’s Building Code: the official page with the current regulation. Fire separations and garage walls are in Part 9; interior finish flame spread is 9.10.17.
- 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.
- 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.
