Snow load on a deck in Ontario: what applies?

Snow Load on an Ontario Deck

The 2024 Ontario Building Code sets the design load for a deck serving a single dwelling unit at the specified roof snow load for the site or 1.9 kPa, whichever is greater. That means the deck is designed for at least 1.9 kPa, or the specified roof snow load if that is greater. Working out that figure for your site is the designer's job, and it goes on the permit drawings.

A few things shape how this plays out for your specific deck:

• Beam, joist and post sizing all follow from the load. The 2024 Ontario Building Code allows Part 9 prescriptive sizing for columns carrying loads from not more than two levels of wood-frame decks where the supported joist length does not exceed 5 m and the combined snow and occupancy load does not exceed 4.8 kPa. Beyond those limits, Part 4 engineered design applies.
• Nothing in Part 9 sizes a deck for a filled hot tub. If a hot tub is going on the deck, confirm with the City's Building Code Services and an engineer before finalising the design.
• The deflection limit for deck beams, joists and decking serving one dwelling unit is 1/240 of the span.

The permit drawings the City of Ottawa requires must show the foundation type, post, beam and joist sizes, spacing and spans, and the deck-to-house connection where applicable. Those drawings, signed off under Schedule 1 by a BCIN designer, an architect, an engineer or the homeowner exemption, are where the snow load calculation gets applied and documented. The City's first permit review takes 5 business days.

If you are comparing two written quotes, lay them side by side and check that each one names the same things: what the footings or piles are (type, depth, diameter), what the decking boards are (species or product, thickness), what the guards and stairs include (height, infill style, number of steps), and whether removal of an existing deck is in scope or excluded.