NBC Stair & Guard Rules: Riser, Run, Handrails, Guards

The requirement

Under the National Building Code, Part 9.8, each riser in a house stair is 125 to 200 mm tall. The run is 255 to 355 mm deep. Guards sit at 900 mm in most spots. The NBC is a model code, so check your province’s edition first.

The riser is how tall each step is. The run is how deep it is, measured from the front edge of one step to the front edge of the next. The minimum run of 255 mm, up to a maximum of 355 mm, gives a tread depth of about 255 to 280 mm.

Every riser in a flight must be close to the same. Two steps next to each other can differ by no more than 6 mm. Across the whole flight, the spread can be no more than 10 mm.

Two more numbers you set out on the job. Headroom is the clear height above the stair. A stair serving a single dwelling unit needs at least 1950 mm. Other stairs need 2050 mm. Then width: a private stair in a single home is at least 860 mm wide. Public or required stairs need 900 mm or more.

Dimension	NBC 2020, Part 9.8
Riser	max 200 mm · min 125 mm
Run	min 255 mm · max 355 mm
Tread depth	about 255–280 mm
Headroom (single dwelling)	min 1950 mm
Width (private stair)	min 860 mm
Handrail height	865–1070 mm to the nosing line

NBC 2020 · 9.8.4

You need a handrail on a private stair once there are more than 2 risers inside. Outside, the trigger is more than 3 risers. Measure the height to a line touching the front edges of the steps. It must sit between 865 mm and 1070 mm.

Guards & barriers

A guard is the barrier on the open side of a stair, landing or floor edge. It stops you falling off. The NBC requires one wherever the drop is more than 600 mm.

Where	Guard height (NBC 9.8.8)
Inside a dwelling unit, and on stair flights	900 mm
Outside guard, single home, surface ≤ 1800 mm above grade	900 mm
Outside guard, single home, surface > 1800 mm above grade	1070 mm
Guard required when the drop is more than	600 mm

The gaps in a required guard on a home also have a limit. A 100 mm ball must not be able to pass through. That keeps a small child from slipping between the bars.

Work it out on site

Say your floor-to-floor height is 2700 mm and you want a stair that works.

Pick how many risers. 2700 ÷ 200 (the tallest a riser can be) = 13.5. You can’t have half a step, so round up to at least 14 risers. 2700 ÷ 14 = 193 mm per step. That is under the 200 limit, so it passes.
Check it’s not too short. 193 mm is well above the 125 mm minimum, so you’re fine.
Set the run. Pick a run of 270 mm. That’s inside the 255–355 range, so it’s comfortable.
Keep them even. All 14 risers must come out within 10 mm of each other across the flight. Mark the stringer carefully.

Change the number of risers or the run until each step lands inside the limits. The calculator does this in one tap.

Do it in 5 seconds

Part of Canada building codes — the NBC, province by province. It shows how the model code becomes law where you build.
NCC stair requirements (Australia) covers the same job under Australia’s code, if you work across both.

Sources

National Building Code of Canada 2020, Part 9.8 — stairs, ramps, handrails and guards (riser and run 9.8.4, headroom and width 9.8.2, handrails 9.8.7, guards 9.8.8). The NBC master copy sits behind a free NRC registration at nrc.canada.ca. Section 9.8 was confirmed against the official BC Building Code, which reproduces it verbatim. (Verified 2026-07-28.)
Adoption caveat — read this before you build. The NBC is a model code. It has no force on its own. Each province and territory adopts and amends it, and Ontario (OBC), Québec, British Columbia (BCBC) and Alberta run their own codes with different numbering and some different figures. So confirm the edition in force in your province, and check whether it has changed the figure you need. The numbers on this page are the NBC 2020, Part 9.8 baseline (unchanged from NBC 2015).

Frequently asked questions

What is the maximum riser height for stairs in Canada?

No taller than 200 mm and no shorter than 125 mm, under the National Building Code, Part 9.8. Steps next to each other must be within 6 mm. The whole flight must stay within 10 mm. The NBC is a model code. Ontario, Québec, BC and Alberta can set a different figure, so check your province's edition.

What is the minimum run (tread depth) for a stair?

The NBC sets a minimum run of 255 mm, up to a maximum of 355 mm. That gives a tread depth of about 255 to 280 mm for a comfortable stair. The run is measured from the front edge of one step to the front edge of the next.

How high does a guard have to be on a house stair?

A guard is required wherever the drop is more than 600 mm. Inside a dwelling unit, and on stair flights, the guard is 900 mm high. An outside guard serving a single home is 900 mm where the surface is 1800 mm or less above the ground, and 1070 mm where it is higher.

Do the NBC numbers apply everywhere in Canada?

Not automatically. The NBC is a model code with no force of its own. Each province and territory adopts and amends it. Ontario, Québec, BC and Alberta run their own codes, with different numbering and some different figures. Always confirm the edition in force where you build.

When do I need a handrail on a house stair?

On a private stair you need a handrail once there are more than 2 risers inside, or more than 3 risers outside. Measure the height to a line touching the front edges of the steps. It must sit between 865 mm and 1070 mm.