Stairs are pure geometry: get the rise and run right and every step feels the same underfoot; get them wrong and you have a trip hazard the inspector will catch. Below we answer the eight deck-stairs-code questions Ontario homeowners ask most. This page is part of our complete guide to building a deck in Ontario.

Getting deck stairs to code: rise, run and equal steps

How do I calculate rise and run so every step is equal?

Measure the total vertical rise from the finished landing to the top of the deck, divide by a comfortable target riser (about 175–190 mm, or 7 inches), and round to whole steps. Then divide the total rise by that number of steps for the exact equal riser. Every riser must land within 6 mm of the others.

1. Measure total rise from the finished landing surface up to the top of the deck boards.
2. Divide by ~180 mm (7″) and round to the nearest whole number — that’s your riser count.
3. Total rise ÷ riser count = the exact, equal rise for every step.
4. Set the run from your tread depth, then check every step is uniform within 6 mm.

What’s the maximum riser and minimum tread per code?

For private deck stairs in Ontario, each step’s rise must be 125–200 mm (about 5 to 7-7/8 inches) and the run at least 255 mm (about 10 inches), with a minimum tread depth of 235 mm. Risers and runs must be uniform — no more than 6 mm variation between steps in a flight.

Why is my bottom step a different height?

Almost always because the tread thickness wasn’t subtracted at the bottom, or the total rise was measured to the wrong point. Measure from the finished landing surface (not bare soil), account for the tread material on the bottom step, and lay out every riser equal. A bottom step off by more than 6 mm fails inspection — and trips people.

Handrails, guards and where they go

How many steps before I need a handrail?

A handrail is required once a deck stair has more than three risers. Below that, a graspable rail isn’t mandatory, though it’s still smart. The handrail must be continuous along the flight and graspable — a 2×4 laid flat doesn’t count as a code handrail, because your hand can’t close around it.

How high should the handrail be?

The handrail height must be 865 to 1,070 mm (about 34 to 42 inches), measured vertically from the nosing of each tread to the top of the rail. It has to be graspable — a proper handrail profile your hand can wrap around — and run continuously the full length of the stairs.

Handrail on one side or both?

For typical private deck stairs, a handrail on one side is the minimum once you have more than three risers. Wider stairs or certain configurations call for both sides. Separately, any open side of stairs more than 600 mm above grade needs a guard — not just a handrail. The guard and handrail are two different requirements.

Don’t confuse the two. The guard stops people falling off the open side and follows the same logic as your deck’s perimeter guard; the handrail is the graspable rail you hold going up and down. Tall stairs often need both at once. The full guard rules are in our deck railing height and guard guide.

Landings and stringers

Do stairs need a landing at the bottom?

Yes. Stairs need a level landing at the bottom (and top) at least as wide as the stairs and about 900 mm long in the direction of travel. On a deck that usually means a concrete pad, patio stones, or a built landing — never bare soil, which settles over winter and throws your bottom riser out of code.

How many stringers, and how far apart?

Most deck stairs use at least three stringers cut from 2×12, spaced no more than about 16 inches apart for 5/4 or composite treads (closer for thin treads, wider for 2x lumber). Wider stairs need more stringers. Each stringer must bear properly on the landing and connect to the deck with rated hardware.

Spacing is driven by the tread material, exactly like joist spacing is driven by your decking. Composite and 5/4 boards flex more, so they want stringers tighter together; full 2x treads can span a little wider. The same span-table thinking runs through the whole deck framing, and your stairs should appear on the drawings you submit.

Frequently asked questions