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Roof access: stairs vs. ladders.

There's a rooftop unit that needs servicing, and someone has to get up there safely with tools. Stair, ship's ladder, or a caged ladder to a hatch? The right answer is set by how often the roof is used and what the code requires — not by whatever's cheapest to bolt on.

// Buyer guide · 2026-07-14 · 5 min read

Exterior steel roof access stair leading to a rooftop equipment area

Short answer: use a stair for roofs accessed regularly or with tools; a ship's ladder when a stair won't fit but access is still frequent; and a caged fixed ladder to a hatch for tight, infrequent, single-worker access. All three are governed by the Ontario Building Code and OHSA — the choice among them is driven by access frequency and what's on the roof.

Start with the question that actually decides it

Not "what's cheapest" — how often does someone go up, and what are they carrying? A rooftop packaged unit on a quarterly service contract, a chiller that needs filter changes, or a green roof that gets walked weekly all imply routine access. Routine access with tools wants a stair. A single roof drain that gets checked once a season doesn't justify a full stair — a ladder to a hatch is proportionate.

The three options, in order of footprint

Roof access stair (~30–38°) — easiest and safest to climb, handles tools and two-way traffic, but needs the most floor area and structure. The default when the roof is worked regularly. Can run interior to a penthouse/hatch or as an exterior tower.
Ship's ladder (50–70°) — a steep-pitch stair that fits where a conventional stair won't. Still climbable facing out with a hand free; a good middle ground for frequent access in a tight space.
Caged fixed ladder (75–90°) — vertical, smallest footprint, with fall protection. Best for infrequent, single-worker access to a roof hatch. Climbed hand-over-hand facing the ladder, so it's not for carrying much.

Don't forget the roof once you're up there

Getting onto the roof safely is only half of it — OHSA requires fall protection at the roof edge and around openings wherever workers go. The usual answer is a non-penetrating (ballasted) guardrail around the maintenance path and the equipment, which protects the worker without a single penetration through the membrane to void a warranty. We did exactly this on a London rooftop — 420 linear feet of ballasted guardrail, no membrane penetrations.

Interior or exterior?

Interior access (to a roof hatch or through a penthouse) keeps everything conditioned and out of the weather, but eats interior floor. Exterior access — a stair tower or ship's ladder up the outside — frees the floor and is common for maintenance-only roofs, with a galvanized finish for the exposure and an engineered wall connection. Neither is "better"; it depends on your building.

Frequently asked

Does rooftop equipment need a stair or is a ladder enough?

It comes down to how often the roof is accessed and by whom. Equipment that needs regular service — RTUs, chillers, anything on a maintenance schedule — is usually best served by a stair or a steep-pitch ship's ladder, which are safer for someone carrying tools. Infrequent, single-worker access can often use a fixed (caged) ladder to a roof hatch. The building code and OHSA set the floor; access frequency sets the practical choice.

What's the difference between a roof access stair, a ship's ladder, and a cage ladder?

A roof access stair is a conventional stair (about 30–38°) — the easiest and safest to climb, but it needs the most floor and structure. A ship's ladder is a steep-pitch stair (50–70°) that saves space where a stair won't fit. A cage ladder is a vertical fixed ladder (75–90°) with fall protection, used for the most space-constrained or infrequent access, typically to a roof hatch.

Do I need a guardrail around rooftop equipment?

Where workers access a roof, OHSA requires fall protection at the roof edge and around openings. A non-penetrating (ballasted) guardrail around the work area and the equipment is the common answer — it protects the maintenance path without drilling the roof membrane. See guardrails & handrails.

Can the roof access go on the outside of the building?

Yes — an exterior stair tower or ship's ladder to the roof is common where interior space is tight or the access is for maintenance only. Exterior access attaches to the building envelope, so the wall connection and the finish (usually galvanized) get engineered for the exposure.

Roof access stairs — fabrication & install
Ship's ladders — the steep-pitch option
Cage ladders — vertical access to a hatch
Guardrails & handrails — roof-edge fall protection