Stair Nosing Sizes: How to Measure and What to Order
Most stair nosing orders that go wrong go wrong on a dimension. This page covers the four measurements that matter — width, floor thickness, length and gap — and what to order against each.
The four numbers
| Measurement | What it decides |
|---|---|
| Width (tread cover) | How much of the tread the nosing sits on. Drives compliance and appearance. |
| Floor thickness | Whether a channel profile will actually accept your covering. |
| Length | Waste, and how many joints appear in a flight. |
| Gap or level difference | Whether you need a nosing at all, or a transition strip. |
Width: how wide a stair nosing do I need?
Width is quoted as tread cover by riser height — a 55 × 55mm profile sits 55mm back on the tread and drops 55mm down the riser.
- 20–36mm — slim profiles for LVT, thin tile and domestic stairs where bulk matters
- 30–40mm — general residential. A common domestic order is 40 × 20mm.
- 50mm — the single most-ordered commercial width, and the usual answer to "what size stair nosing do I need" for an office or shop
- 55 × 55mm — the figure to work to where Approved Document M applies, in buildings other than dwellings
- 70–100mm — industrial, and retrofit over a damaged edge where you need to cover more of the tread
Measure the going first. The nosing has to leave a comfortable walking surface behind it, so a 70mm profile on a shallow domestic tread is the wrong answer even if it fits. And check the projection: Approved Document K works to a maximum of 25mm overhang over the tread below.
Browse by width in the aluminium range.
Floor thickness: matching the channel
If your profile has a channel that captures the floor covering — standard for LVT, vinyl, laminate and tile — the channel depth has to match the covering, not approximately but properly.
Measure the total build-up: the covering, plus any attached backing, plus the adhesive bed, which is typically 1–2mm. Order a channel about 0.5mm deeper than that total.
- 3mm LVT — a compact profile such as a 40 × 26mm channel
- 5mm click LVT — a deeper channel; 5mm is the most common click-vinyl thickness
- 7–8mm laminate — a push-in profile that clips into the machined lip of the board, or a channel sized to the board plus underlay
- 10mm and 12mm tile — tile-in profiles are specified directly by tile thickness. Tile-in range.
- Carpet — measure pile plus underlay compressed. Domestic pile over underlay is usually 10–15mm; contract carpet without underlay 6–9mm. Carpet range.
Too shallow and the covering sits proud, creating the lip you were trying to remove. Too deep and the edge is unsupported and crushes. See the vinyl and LVT range for channel profiles.
Length: what comes in what
- 900mm — a common single-step length, and the usual answer to a "90cm stair nosing" search. Useful for one or two steps without cutting down a 2.7m bar.
- 1m, 1.5m, 2m, 2.5m — typical retro-fit and GRP lengths
- 2.44m, 2.7m, 2.75m, 3m, 3.22m — standard aluminium extrusion lengths
- 400mm to 3m — typical GRP range
- Cut to length — available on most profiles, and worth it on a large flight because it removes site waste and speeds fitting
Measure every step individually. Flight widths commonly vary by several millimetres in older buildings, and cutting a whole set to one length means some bind and some leave gaps. Leave 2–3mm clearance at each end for thermal movement.
Gaps and level differences: when you do not need a nosing
A common search is for a specific gap — "15mm gap", for instance. If you are bridging a gap or a level change between two floors rather than protecting a step edge, a stair nosing is the wrong product.
- Same-height junction between two coverings — a transition or threshold strip. Some are made specifically to span a set gap width.
- Different heights, up to a few millimetres — a ramp reducer, which slopes from the lower floor to the higher one.
- A doorway — a door threshold or door bar.
- An actual step — then you want a stair nosing, and the width guidance above applies.
See same-height transition strips or door thresholds for those cases.
Gauge: the number people forget
Gauge is the metal thickness of the extrusion, and on a busy stair it matters more than width. 1.5mm suits light domestic duty, 2.5–3mm general commercial work, and 5mm industrial stairs with wheeled traffic. A profile that is wide but thin will dish at the leading edge under trolleys. See the heavyweight range for 5mm sections.
Frequently asked questions
What is the most common stair nosing size?
50mm tread cover for commercial stairs and 30–40mm for domestic. Where Approved Document M applies, 55 × 55mm is the specification figure.
What size nosing for 7mm laminate?
Either a push-in profile that clips into the board's machined lip, or a channel profile sized to the board plus any underlay. Measure the total build-up rather than the board alone.
Do you supply 900mm stair nosings?
Yes. 900mm is a standard single-step length on several profiles, and most others can be cut to length. It is usually cheaper than buying a 2.7m bar for one or two steps.
I need to cover a 15mm gap — which product?
If it is a gap between two floor coverings rather than a step, you want a transition or threshold strip, not a stair nosing. Some are made specifically to span a given gap width.
How do I measure my step for a nosing?
Three numbers: the width wall to wall, the depth of the tread (the going), and the thickness of the floor covering including adhesive. Those three settle profile width, channel depth and length.
Can nosings be cut to length on site?
Yes — aluminium, GRP, brass and PVC all cut with the right blade. Support the profile both sides of the cut, file the end, and touch in exposed cuts on coated aluminium. See the installation guide.
Not sure which size you need? Send us the step width, the going and what the stair is finished in, and we will specify against it — or call 01282 270 010. For compliance dimensions see the building regulations guide.