Does Ontario's Code say how far apart studs must be for drywall?

Ontario's Building Code does not give a stud spacing number for drywall. What it does is set the maximum spacing of supports in Table 9.29.5.3, which varies by board thickness, whether the board runs across or parallel to the framing, and whether the surface will be painted or textured. The table tells you the limit; it does not tell you which board to choose or how the framing is laid out.

The clause that governs this (9.29.5.1) also limits its own scope: the rules apply to a single layer of gypsum board on wood furring or framing, fastened with nails or screws. If the framing is steel, if there are multiple layers, or if adhesive is involved, the Code points instead to CSA A82.31-M, "Gypsum Board Application". These are minimums for new work, and the City of Ottawa decides how they apply to your renovation, so it is worth asking Building Code Services before the board goes up.

In practice, the board thickness and the framing spacing have to match. Ask the contractor which board they are specifying and confirm it suits the framing already in place. If the framing is being changed at the same time, that is structural work and belongs to a separate conversation with the City about whether a permit applies.

What to have on paper before work starts: a written contract that names the board thickness and type, the scope of work, the total price, and the start and completion dates.