Accessible Approaches: Ramps, Doors and Steps

A ramp's gradient is tied to the length of the flight

Pushing a wheelchair up a slope is hard in proportion to both its steepness and its length, so Approved Document M does not give one maximum gradient: it gives three points and a line between them. A flight with a 10 m going may be 1:20, one with a 5 m going 1:15, and one with a 2 m going 1:12, and for goings in between the gradient may be interpolated — 1:14 for 4 m, 1:19 for 9 m. The line through those points is a gradient of 1 in (going + 10), and it keeps every flight to a rise of 500 mm at most.

Read the other way, a chosen gradient fixes the longest flight: 1 in n allows a going of (n − 10) m and a rise of (n − 10) ÷ n. A total rise is divided into as few equal flights as that allows, with a landing at the foot and head at least 1.2 m long and one between each pair of flights at least 1.5 m long. The ADA works differently — 1:12 at the steepest for a run of any length, with a landing every 30 in (760 mm) of rise — so the same change in level takes a longer approach in England.

Steps beside a ramp, and a lift beyond two metres

A ramp is not the best approach for everyone. Some people who can walk find a ramp harder than steps, and a wet ramp is a slip risk, so where a ramp rises more than 300 mm — two steps' worth — Approved Document M asks for clearly signed steps as well. And where the total rise is more than 2 m, a ramp alone is too tiring however many landings it has, and wheelchair users need an alternative such as a lift.

Two wheelchairs cannot pass on a ramp 1.5 m wide, so where one end cannot be seen from the other, or there are three flights or more, landings at least 1800 mm square are needed as passing places. The pages count these as consequences of the layout rather than as extra inputs, because they follow from the rise and the gradient.

A door's width is the width you can pass through

The figure that matters is the effective clear width, not the size of the door leaf. Approved Document M measures it at right angles to the wall, from the door stop on the closing side to whatever projects furthest on the hinge side — the open door, its handle, a weather board. Its Table 2 then asks for 800 mm on a straight approach or a turn from a route at least 1500 mm wide, 825 mm for a turn from a route only 1200 mm wide, and 1000 mm for the external door of a building the public uses, with smaller figures for existing buildings.

The ADA measures between the face of the door and the stop with the door open 90 degrees, and asks for 32 in (815 mm), or 36 in (915 mm) where the opening is more than 24 in (610 mm) deep. The two rules measure different lines, so a reading taken one way is not the other's figure.

An external step has a range, not a figure

Approved Document M asks each external step to rise between 150 and 170 mm and each going to be between 280 and 425 mm, the same on every step of a flight. The rise of a flight is split into equal steps — which is what keeps the rise consistent — and a flight may have no more than 12 risers where the going is under 350 mm, or 18 where it is 350 mm or more, with a level landing at least 1200 mm long at the top, the bottom and between flights. A single step is not allowed at all, because on its own it is easy to miss.

What none of these pages decides

Each page applies a dimension a document publishes. None of them decides whether a building is accessible: that depends on the whole route from the street to the room, on handrails, surfaces, contrast, lighting, signage and management as much as on any width or gradient, and in England it is building control's decision against the requirement itself. So the pages lay out, compare and count, name the rule each figure comes from, and stop there.