Gradients – quick reference guide

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Measuring gradients:Three surfaces with different angles shown. On left, a horizontal line labelled angle 0 degrees, gradient 0:0, gradient percent 0% Centre, an acute angle with labels for angle, going (hypotenuse, surface), rise (vertical), run (horizontal) has calculations: angle: 5 degrees, gradient equals rise:run equals 1:12, gradient % equals rise/run x 100 equals 1/12 x 100 = 8% On right, angle drawn equals 45 degrees, gradient equals 1:1, gradient % equals 100%

Key gradients for accessibility:

Angles of essential gradients for public realm infrastructure are small. This makes them hard to assess on images, but small surface gradient changes make huge differences to accessibility. The below diagrams show requirements and implications of different gradients for accessibility.

1:100 – 1:50, 1-2%:

Walking/wheeling and cycling route crossfall, max slope for parking spaces (1:40, 2.5% is absolute max crossfall gradient).

A 1:100 gradient slope rising to the right. A person using a long cane and a person riding a mobility scooter are moving away from the viewer. The slope is small but can be noticed especially for the mobility scooter user.

<1:60, <1.6%:

“Level” ground for public realm.

A 1:60 slope rising to the right. A person using a rollator accompanying two children is walking towards the viewer, while a person on an adult tricycle is moving away from the viewer. The slope is noticeable - all these people are at an obvious angle.

1:20 – 1:12, 5-8%:

Ramp, see building regs part M for max lengths, handrails, surfaces etc. Lateral tip hazard – designs must not require traversing ramps.

A 1:20 slope rising to the right. A manual wheelchair user is going up the slope, putting in obvious effort to move.

>1:10, >10%:

Inaccessible for many users. Forwards/backwards tip hazard. (1:10, 10% is absolute maximum ramp gradient for maximum 1m going).

A 1:10 slope rising to the right. A mobility scooter user is moving up the slope. A 1m marking in bright red on the slope under the mobility scooter user indicates the absolute maximum permitted length of a 1:10 ramp is no longer than a single mobility scooter.

Gradients are hard to assess on drawings and photos, but they are critical for real-life accessibility.

References

BS8300-1,

Inclusive Mobility (2021),

Building Regulations Approved Document M

A graphic version of this quick guide is available here

For further details on accessibility and gradients, see our crossfall quick guide.

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