Measuring ramps and auditing on site

1. What to carry

You do not need much, and everything here fits in a small bag. The first three are non negotiable.

• A digital level, 600mm long. Also sold as a smart level or an electronic level. This is the single most useful tool you will own. Get one that reads in percent, not only degrees.
• A tape measure, 5m or 8m. A metal one that stays rigid when extended saves a lot of frustration when measuring alone.
• A camera. Your phone is fine. Photographs are your evidence.
• A door pressure gauge if you can get one, for checking how much force it takes to open a door.
• A light meter or a phone app, for checking lighting levels at signage and stairs.
• A notebook or a tablet with your recording sheet ready to fill in.
• Chalk or removable tape to mark measuring points so your photos line up with your notes.

2. Understanding slope

Slope is just how much a surface rises compared to how far it travels. Two measurements, one relationship.

• Rise. How much it goes up, measured vertically.
• Run, sometimes called the going. How far it travels, measured horizontally.

The same slope gets written three different ways, and you need all three.

Learn this table. It covers almost everything you will meet.

3. Running slope and cross slope

Every sloped surface has two slopes and people forget the second one constantly.

• Running slope is along the direction you travel. This is the one everybody thinks of. Measure it pointing up and down the ramp.
• Cross slope is side to side, across your direction of travel. Measure it by turning the level 90 degrees.

Cross slope matters because it is exhausting and it is dangerous. If a path tilts sideways, a wheelchair constantly veers downhill, so the user has to brake one wheel the whole way to travel in a straight line. On a wet tiled surface it is a fall risk for someone with a walking stick. A path can have a perfect running slope and still be unusable because of cross slope.

Keep the reference visible: ISO 21542:2021 clause 6.3.7 recommends drainage cross-fall no greater than 1:50 (2%), with an exceptional-circumstances qualification. ADA 405.3 sets ramp cross slope at 1:48 (about 2.083%) maximum. These are different boundaries. Drainage must also prevent water collecting on the route.

4. Measuring a ramp with a digital level

This is the method to use whenever you have the tool.

Then repeat the whole thing with the level turned sideways for cross slope, and take a reading at the top and bottom landings too, because landings are supposed to be level and frequently are not.

5. If you have no digital level

You can get an accurate answer with a plain 600mm spirit level, a tape measure and a pencil. This is worth knowing because it also explains what the digital level is calculating for you.

If you work in imperial, the equivalent with a 24 inch level is a gap of 2 inches for 1:12 and half an inch for 1:48. Same idea, different units.

6. Check a named ramp standard

A ramp is a route with landings, usable edges, sufficient space and a dependable surface. First record the applicable standard, edition and project scope. The comparison below uses ISO 21542:2021 ordinary ramps (Table 6) and the 2010 ADA ramp provisions. It does not apply existing-building or kerb-ramp exceptions automatically.

Read the ISO edition record and ADA section 405. The ISO detail here was checked against the supplied licensed 2021 edition. The full standard and the applicable local requirements still determine the project assessment.

Measure the clear approach as carefully as the ramp. Check door operation, direction changes, resting space, drainage, lighting, rails and the risk of falling from the sides. A slope result describes one measurement; it cannot certify the complete route.

7. Worked examples with a stated reference

8. Use the ramp planner

For a quick manual check, a 300mm rise over 6000mm horizontal run gives 300 ÷ 6000 × 100 = 5%, or 1:20, and an angle of about 2.86°. The ramp surface is about 6007mm long. End landings are additional plan space; they are not part of the sloping run.

9. Steps and stairs

A ramp is not always the answer. For a big rise a compliant ramp becomes enormous, and plenty of people find a well built stair easier than a long slope, so most places need both. Stairs have their own numbers, and they come off the same tape.

Two measurements describe a step. The riser is the height of one step, and the going is the depth of one tread, front to back. Everything else follows from those two, including the pitch and 2R + G, two risers plus one going. The explorer below uses an illustrative 550–700mm proportion band, a 150–170mm riser range and a 250–450mm going range. These are teaching heuristics, not a combined ISO, ADA or local-code assessment.

10. Other measurements, with their references

Write the reference next to the number. A door opening, an approach space and a wheelchair turning area serve different movements; one cannot stand in for another. Rounded unit labels are also not interchangeable minimums: 1500mm is less than 60in.

ISO references in this table mean the 2021 edition. See the physical accessibility guide for the complete journey and source map. All heights are measured from finished floor level, including the installed floor covering.

11. Running the audit itself

The most common way to produce a bad audit is to wander around measuring interesting things. Follow the journey instead. Walk the building the way a visitor experiences it, in order, and audit each stage as you reach it.

How to record a measurement so it is still useful next month

Every recorded item should carry these seven things. Missing any one of them creates an argument later.

1. Where. Be specific. "Main entrance ramp, upper third" beats "entrance".
2. What. The element, such as running slope, clear width, counter height.
3. The number and the unit. Pick metric or imperial and stay in it for the whole report.
4. The requirement you compared it to, and which standard that comes from.
5. Pass or fail, and by how much. "Fails by 15mm" tells someone this is a trim job. "Fails by 400mm" tells them it is a rebuild.
6. A photograph, ideally with the tape or level in shot showing the reading.
7. Date and who measured it.

Do the non measurable checks too

Not everything has a number, and the things that do not are often what actually ruins a visit. While you are on site, look for these.

• Is the accessible toilet being used as a store room? This is extremely common.
• Is the accessible parking bay the furthest from the door, or blocked by cones?
• Does the ramp lead to a door that is kept locked?
• Do staff know where the portable ramp is, and can they find the key for the lift?
• Is the hearing loop switched on and does anyone know how to test it?
• Is the accessible route signposted from the point where you have to choose?

12. Mistakes to avoid

• Measuring once. Surfaces vary. Three readings minimum, always report the worst.
• Forgetting cross slope. Turn the level sideways every time.
• Measuring the door frame. The clear opening is smaller than the frame, because the door leaf sits in the way. Always open it to 90 degrees first.
• Averaging readings. Users have to negotiate the worst point, not the average point.
• Mixing units mid report. Decide at the start and stay consistent.
• Trusting an uncalibrated level. Calibrate daily.
• Only checking the way in. Getting out in an emergency is part of the audit.
• Writing "not compliant" with no number. Always record the actual measurement, the target, and the gap between them.

13. A record sheet to take with you

Everything above only helps if it gets written down at the time. Memory is not a measuring tool. Print this, put it on a clipboard, and fill in a copy for every ramp and every entrance you look at. One sheet per element, so nothing gets merged by accident.

Two habits make the sheet worth having. Always write the number you actually measured, even when it passes, because the next person needs a baseline. And when a measurement is outside the selected requirement, write the number and the relevant clause. A redesign needs the whole layout: simply adding ramp length may introduce new landing, turning or door-clearance problems.

The last box matters more than it looks. Photograph every failure with something in shot for scale, a tape or the level itself, and note the file number on the sheet. A photograph with a tape measure in it ends arguments that a paragraph never will.