How to measure the floor opening

Record length, width, edge position, slab thickness and any beams. Do not confuse finished clear dimensions with structural dimensions.

Why this parameter matters

Stair geometry is a system of dependencies: changing one dimension affects riser count, run, pitch, headroom and footprint. A single number should not be judged in isolation.

How to check it in practice

1. Record all measurements in centimetres and mark whether they are structural or finished.
2. Run at least two integer riser-count options.
3. Check 2h+s, pitch, width, headroom and risers per flight.
4. Verify the result on site and in the project documentation.

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