Framing is where a deck earns its safety. Get the spans right, connect it properly, and brace it — and it stays solid for decades. Below we answer the ten framing questions homeowners ask most. This page is part of our complete guide to building a deck in Ontario.

How far can joists and beams span?

Use the finder to get a starting joist size for your span, then confirm it against the full tables below.

What size joists and beams do I need, and how far can they span?

It comes from the span tables, not guesswork. A guarded deck needs at least a 2×8 joist. Here are common maximum joist spans (S-P-F No.1/No.2, with bridging) — use the shorter of this and your town’s deck guide:

And the beam (the distance between posts), built-up S-P-F supporting joists up to 3.6 m (11′-10″), per OBC Table 9.23.4.2.-H:

Does 16″ vs 12″ on-centre matter?

Yes. 16″ o.c. is the standard and supports most decking. Going to 12″ o.c. makes the deck noticeably stiffer, lets you use 5/4 decking, and is required for many diagonal composite installs. Wider than 16″ weakens the deck and limits your board choices.

Posts, spacing and cantilevers

How far apart can my posts be?

Post spacing is set by your beam, not by feel. Pick a beam size and number of plies, read its maximum span from the table above, and that’s the maximum distance between posts. Bigger beam or more plies = posts further apart; smaller beam = more posts and footings.

4×4 vs 6×6 posts — which do I need?

Use a 6×6 for any guarded deck. It satisfies every Ontario municipality, meets the building-code column minimum, and is required for bearing under a 3-ply beam. A 4×4 is below the column minimum and only defensible on a low, unguarded deck where it’s explicitly allowed.

How far can the deck cantilever past the beam?

Use absolute limits, not the US “quarter of the backspan” rule. A 2×8 joist can cantilever up to 16″; a 2×10 or 2×12 up to 24″. The beam itself can overhang the end post by about 12″. Add any cantilever length to the joist span when you size the beam.

Beam on top of posts vs bolted to the side (saddle vs notch)?

Best practice is a beam sitting on the post in a galvanized saddle/cap, or a notched 6×6 capturing all beam plies and bolted through. Both resist uplift and give at least 3.5″ of bearing. A beam simply lag-screwed to the side of a post is weaker and gets flagged.

Stiff, solid framing

My deck is bouncy and wobbly — how do I stiffen it?

Bounce is almost always under-sized joists, posts spaced too far apart, missing mid-span blocking, or no bracing. The cheapest cures, in order: add a mid-span beam-and-post line, add a row of solid blocking between joists, and add diagonal bracing on the posts.

Do I need diagonal knee bracing and lateral bracing?

Yes — any deck or post more than 600 mm above grade needs diagonal (knee) bracing to stop sway. Use at least a 2×4 brace at roughly 45 degrees, bolted with a 3/4″ through-bolt. Don’t rely on US hold-down figures; follow your municipality’s bracing requirement.

Are joist hangers required, and which nails or screws?

Where joists meet the ledger or a flush beam, use galvanized joist hangers and fill every hole with the manufacturer’s galvanized hanger nails. Deck screws and roofing nails are not rated for hangers. Match the connector metal to the fasteners to avoid corrosion with treated wood.

How do I frame a tall, walkout-basement or second-storey deck?

Tall decks need taller posts (6×6), more bracing, and careful guard-post anchoring — and over about 10 feet or with unusual loads they need an engineer. A walkout deck off the house also needs a proper ledger and flashing; see our attaching a deck to the house guide.