Stair and Landing Forms

Written for Canada. Plans are metric, but many crews and suppliers work in feet and inches, so this site gives both: millimetres and metres, with feet and inches beside them. Codes are the National Building Code of Canada 2020 (NBC 2020) Part 9 as your province adopts it. A number marked Confirm has not been checked against every province, so check it with your own authority before you act on it.

Reviewed by a working tradesman with 17+ years in the field.

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Forms for concrete steps and landings, built so every rise and every run matches.

The big idea

Concrete stairs and landings have no second chance. Measure the total rise carefully, divide it equally, and check every step before you pour. Rise, run, handrails and guards come from NBC Part 9, Section 9.8 as your province adopts it, or from the drawings.

Types of concrete stairs and landings

• Monolithic stairs: poured with the slab or landing.
• Independent stairs: poured separately and tied or isolated from the building as drawn.
• Exterior stairs: need drainage, frost design and a slip-resistant finish.
• Commercial stairs: heavily reinforced, with engineered dimensions.
• Landing slabs: flat platforms at doors and changes of direction.

Critical dimensions

Under the model code (NBC Part 9, Section 9.8, read in the Vancouver Building Bylaw 2014):

• Handrails are 865 to 965 mm (34 to 38 in) high, measured from the nosing line (9.8.7.4). Not required on interior stairs of one dwelling unit with 2 or fewer risers, or exterior stairs with 3 or fewer risers (9.8.7.1).
• Guards are required where the difference in level exceeds 600 mm (23 5/8 in), or the adjacent slope is steeper than 1 in 2 (9.8.8.1).
• Landing height must match the floor or slab it meets.

Worked example: a 1,100 mm rise

The landing sits 1,100 mm (43 1/4 in) above the lower slab, and the stair is private, so the maximum rise is 200 mm.

1. Count the risers. 1,100 ÷ 200 = 5.5, so round up to 6 risers.
2. Divide equally. 1,100 ÷ 6 = 183.3 mm per riser, about 7 1/4 in. Each is inside the 125 to 200 mm limit.
3. Pick the riser board. A 38 x 140 mm (2x6) is only 140 mm tall, so it is too short. A 38 x 184 mm (2x8) is 7 1/4 in, which fits. Or rip plywood to the riser height.
4. Count the treads. The top step is the landing, so there are 6 − 1 = 5 treads.
5. Set the run. At 260 mm (10 1/4 in) per run, the total run is 5 × 260 = 1,300 mm, about 4 ft 3 in.
6. Check the tolerance. Measure each riser. They may differ by 5 mm (3/16 in) between neighbours and 10 mm (3/8 in) across the flight. Aim for all six to read 183 mm.

Base preparation

• Remove topsoil and organic material.
• Compact the subgrade thoroughly.
• Place and compact granular base, shaped to the stair profile.
• Where exterior stairs attach to a heated building, check the frost design. They may need to bear below frost or be isolated. Confirm with the drawings and the inspector.
• Place a vapour barrier for interior landings where required.

Forming materials

• Lumber for risers and edges, sized to the step height (see the example above).
• Plywood for closed risers and side panels.
• Stakes, screws and bracing.
• String lines and laser for elevations.
• Rebar, mesh and chairs as drawn.

Building stair forms

1. Measure the total rise. From the lower surface to the upper surface or landing.
2. Divide it equally. Pick a rise within the code limit, then set the run.
3. Snap the layout lines. Edges, landing boundary and step positions.
4. Build the risers. Boards at each step height, with the nosing profile built in.
5. Build the side forms. Straight and plumb.
6. Brace. Stairs create strong pressure at the lower steps during the pour.
7. Check every step. Rise and run, before the reinforcement goes in.

Landing forming

• Landings are level unless the drawings call for a slope.
• Set the perimeter forms to the exact elevation, and stake them tightly.
• Place rebar or mesh as drawn.
• Make sure the landing ties into the stairs as designed.
• On exterior landings, set the slope to drain that the drawings give.

Reinforcement and pouring

• Bars in treads and risers as drawn, mats or mesh in landings, dowels tying stairs to slabs or walls, and chairs to hold the steel at the right height.
• Work from the bottom step up, filling evenly.
• Vibrate to remove air pockets, especially under nosings.
• Watch the risers for movement.
• Finish treads with a slip-resistant texture, especially outdoors.
• Check nosing alignment during finishing.

Common mistakes

• Inconsistent rise or run
• Wrong landing elevation
• Weak bracing and blowouts at risers
• Rebar touching the form
• Steps out of square
• A smooth finish on exterior steps
• No handrail or guard where the code requires one