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Exterior steps serving one home are "private stairs" in the Ontario Building Code. The rise and run limits and the handrail rule are on our Ontario deck code guide, linked below. These are the rules that matter when steps are rebuilt, checked against the Ministry's 2024 Building Code Compendium and the Ontario Amendments dated July 17, 2026, which leave each of them in place. O. Reg. 325/26 has since re-dated that document to October 1, 2026, and we have not re-checked these figures against that edition. Steps have to match each other. Risers in one flight may differ by no more than 5 mm between neighbours and 10 mm between the tallest and the shortest. Treads follow the same 5 mm and 10 mm limits for their run, and no tread may slope more than 1 in 50 (9.8.4.4.). So a replacement tread thicker or thinner than the old one changes the rise of the step above it and the step below it. That is our arithmetic, not the Code's wording. The front edge of each tread is rounded or bevelled by 6 mm to 14 mm (9.8.4.8.). A landing is needed at the top and bottom of each flight and wherever a door opens onto the stair (9.8.6.2.). Level ground or a floor at the top or bottom, sloping no more than 1 in 50, counts as a landing (9.8.6.1.). At a side or back door of a single home, the top landing may be left out if the stair has no more than three risers, the door slides or swings away from the stair, and any storm or screen door that swings over it has hardware to hold it open. Where a door swings toward the stair, its full swing has to be over the landing (9.8.6.3.). Underneath, stairs for one home are designed for 1.9 kPa (9.8.9.1.). Wood steps may not sit in direct contact with the ground unless they are treated with a wood preservative (9.8.9.3.). Wooden stringers have at least 90 mm of wood left at the deepest cut and an overall depth of at least 235 mm (9 1/4 inches), are supported and secured at top and bottom, and are spaced no more than 900 mm apart on stairs for one home. Where the risers hold up the front of the treads, that spacing may go to 1 200 mm (9.8.9.4.). The Code sends the depth of foundations for exterior steps to Section 9.12, the same footing rules as a deck (9.8.9.2.(3)). The tread surface has to be wear-resistant, slip-resistant, smooth, even and free from open defects (9.8.9.6.). There is one allowance for existing homes. The Code's part on renovating existing buildings (Part 11) applies to repair, and its compliance alternative C112 says a replacement of an existing stair system is exempt from Subsections 9.8.1 to 9.8.4, which hold the rise and run rules and the limits on how far steps may differ, as long as it keeps at least 700 mm between wall faces and 1 800 mm of headroom over the nosings or landing.For a house, it can be used without first showing the chief building official that full compliance is impracticable (11.5.1.1.(2)). It does not reach the landing, stringer, ground-contact or finish rules above. Permits. The Building Code Act defines "construct" to include repair (s.1(1)) and says no one may construct a building without a permit (s.8(1)). None of the ten towns Peter serves names steps or stairs in its own list of what needs a permit. This is what each says about repairs and porches. Niagara Falls lists "Guard/railing replacement or new installation", "Repairs to structural members" and "Replacing structures in same size and the same location" among the work that needs a permit. Port Colborne lists "Structural alterations or repairs". Pelham's permit guide says construction "can include anything in the erection, installation or extension or material alteration or repair of a building." Thorold says a permit is required for repairs but is "Not required for some minor repairs", and lists porches among the structures over 10 m2 that need one.Grimsby says minor repairs typically do not need one and structural changes do. Niagara-on-the-Lake's brochure says permits are required "for all exterior and interior construction", with sheds and small accessory buildings exempt. St. Catharines says covered decks and porches always need a permit. Fort Erie says an attached deck, porch, pergola or verandah needs one. Welland and West Lincoln: we found nothing on their sites about repairing steps. Where a step job falls between a minor repair and a structural one is the building department's call, not ours. Ask the town before the work starts, and say whether the stringers or the railing are being replaced.
A porch has a roof over it. Its steps usually do not. In the Journal of Light Construction, builder Emanuel Silva describes a porch stair that "is usually exposed to the weather and takes a licking over time," with "loose or cracked treads, shaky railings, and wobbly newel posts" as the result. On the stair he rebuilt, the cause was water held against the wood: "dirt had collected between the tread and the posts, trapping the moisture," and one stringer had started to rot. Start with a screwdriver. This Old House contractor Tom Silva recommends probing suspect wood with one, "looking for soft, flaking, crumbling, or damp spots," and the same guide says rot starts where moisture collects, at corners and joints. On a set of steps, that means the ends of each tread where it sits on the stringers, and the foot of each stringer where it meets the ground or the pad. A tread is the smaller job. This Old House's stair-tread guide says a cracked or split tread can often be fixed without replacing the board. It says to replace the tread if "the wood is soft, spongy, or shows signs of rot," if it has several large cracks, if it has warped or is no longer level, or if an earlier repair has failed. The stringers decide the size of the job. This Old House's stringer guide says to replace stringers that have extensive rot or insect damage, large cracks or splits, or severe warping. A stringer that has only sagged can get added support underneath. Emanuel Silva's JLC repair is the middle path: he cut out the rotted section, fastened pressure-treated stock to the side of the damaged stringer, and coated every fresh cut with wood preservative. Then build it to shed water. Those guides call for screws rather than nails on treads and risers, stainless or hot-dipped galvanized fasteners, pressure-treated or naturally rot-resistant wood outdoors, and a slight slope on exterior treads, about 1/8 inch per foot, so water runs off. That slope is about 1 in 96, inside the Code's limit of 1 in 50 for a tread. A step that rocks in October is still rocking in January, with ice on it. Peter repairs porch steps, alongside the decks, fences, pergolas and sheds he builds across Niagara. If a step has gone soft or moves underfoot, send him a photo of the step and of the bottom of the stringers through the contact details below, and say which town you are in.
Push a screwdriver into the wood. This Old House's Tom Silva looks for soft, flaking, crumbling or damp spots. Check the tread ends where they sit on the stringers and the bottom of each stringer where it meets the ground or pad, since rot starts where water collects.
A soft, spongy or rotted tread is replaced on its own. Stringers are replaced when rot or insect damage is extensive, or when they have cracked or warped badly. A stringer with a small rotted section can have it cut out and new pressure-treated wood fastened along its side.
Under 9.8.4.4. of the Building Code, risers in one flight may differ by no more than 5 mm from the next one and 10 mm from the tallest to the shortest. Treads have the same limits for their run. A replacement tread of a different thickness changes the rise of the steps on either side of it.
None of the ten towns names steps in its permit list. Niagara Falls and Port Colborne list structural repairs as needing a permit, and Niagara Falls also lists guard or railing replacement. Thorold and Grimsby say some minor repairs do not need one. Ask your town before starting, and say what is being replaced.
Not unless the wood is treated with a preservative. Article 9.8.9.3. of the Building Code says exterior wood steps shall not be in direct contact with the ground unless suitably treated.
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