How to measure for a straight steel staircase
A straight stair is fixed by the building around it. Record finished-floor levels, the full horizontal run, opening geometry, headroom, landing edges and the real supporting structure before the workshop sets out the flight. This guide gives the measuring order, the checks that expose a sloping or non-square opening, and the information that belongs with your site sketch.
A straight steel staircase must fit three things at once: the height between floors, the horizontal space available and the opening through which a person walks. Measure those constraints before choosing a tread count or stringer shape. The workshop can then set out a made-to-measure flight from facts rather than from an assumed standard size. Straight flights, landings and access steps are grouped under stairs and access.
Prepare the site before measuring
Use millimetres throughout. Take a laser, steel tape, spirit level, plumb line and a sketch pad. Mark a fixed reference, such as a structural wall or grid line, that will still exist when finishes are installed. Photograph every end of the proposed flight and place the tape in some photographs so the scale is visible.
Do not mix drawing dimensions with site dimensions without labelling them. A design drawing describes intent, while the built opening may have moved. Note the date, room and revision on every sheet. If screed, tile, timber flooring, plasterboard or wall lining is unfinished, record its proposed thickness separately instead of hiding it inside a guessed clear dimension.
Measure the total rise between finished floors
Measure vertically from the finished walking surface below to the finished walking surface above. This is the total rise. If either finish is absent, list the build-up layer by layer and calculate the future level. Repeat the rise at both sides of the proposed stair and near the centre. A slab, landing or timber floor can slope, and the workshop needs all readings rather than a convenient average.
- Mark the lower finished-floor level.
- Transfer the upper finished-floor level vertically with a laser or plumb reference.
- Record the measured rise and every uninstalled finish.
- Repeat the measurement independently before sending it.
Do not choose the individual rise yourself by dividing the height into a preferred number of steps. The designer must coordinate rise, going, pitch, clear width and headroom under the rules that apply to the building. In England and Wales that normally means the current Approved Document K for building work. Other uses and countries have different requirements.
Record the available run and both landings
The available run is the horizontal distance, not the sloping distance along the stair. Measure from the proposed face of the first riser to the landing edge or other agreed top reference. Show doors, radiators, columns and circulation paths around the bottom and top. A door that opens across the first tread can make an otherwise geometrically valid staircase unusable.
At the top, record the landing length and width, the exact nosing or slab edge and the direction in which users leave the flight. At the bottom, show the clear approach. If the stair turns through a landing before or after the straight flight, measure that landing as its own rectangle with both diagonals.
Measure the floor opening and headroom
For a stair below an upper floor, measure the clear opening between finished faces. Take its length at both sides, its width at both ends and both diagonals. Unequal diagonals reveal that the opening is not square. Record the slab or floor thickness, including beams, downstands, ducts and ceiling linings below it.
Headroom is checked vertically above the pitch line and tread nosings, not perpendicular to the stringer. A short opening may leave adequate space at the landing but too little where a person passes below the opening edge. Supply a side elevation showing the underside of the floor, the opening edge and every obstruction. The stair designer then checks the walking line against the applicable rule.
Identify supports and fixing faces
Show what the stair will bear on at the bottom and top: reinforced concrete, structural steel, masonry or timber. Tile, floating screed, plasterboard and floorboards are finishes, not proof of a supporting member. Record the structural thickness where known and locate free edges, joints, reinforcement zones, services and waterproofing.
Do not choose anchors from the stair weight alone. Connection forces also depend on geometry and use. The structural engineer and the selected anchor manufacturer's current data are the authority for anchors into concrete, brick, aerated block or timber. If a new beam or trimming frame is needed, it belongs in the design of the supporting steel structure before the stair hole pattern is approved.
Check guards and interfaces
Mark every open side, landing edge and floor opening that needs guarding. Give the intended mounting face and finished levels. The required height, gaps and loads depend on the country, building type and use, so do not copy a dimension from another house. Coordinate the stair with the chosen railing or balustrade as one assembly.
What to put on the survey sketch
| Item | Record |
|---|---|
| Total rise | Finished floor to finished floor, at several positions |
| Available run | Horizontal distance between agreed bottom and top references |
| Opening | Length, width, both diagonals and finished lining |
| Floor depth | Slab or joists, ceiling, beams and downstands |
| Headroom obstacles | Opening edge, beams, ducts, roof slopes and lights |
| Landings | Clear sizes, edges, doors and direction of travel |
| Supports | Actual structural material, thickness and free edges |
| Access | Doorways, turns and the route for bringing sections in |
Before you approve fabrication
Compare the workshop drawing with the site, not just with your first sketch. Confirm units, finished levels, overall rise, run, opening, handing, support faces, joint positions and coating. Never scale a missing dimension from a PDF. Ask for it to be stated. Recheck the building after wet trades and linings are complete, because the final opening is the one the stair must fit.
Keep the dated survey and approved revision together. If delivery or assembly details remain unclear, check the current frequently asked questions before sign-off. Once steel is cut to an approved dimension, a site change cannot be solved by stretching the flight.