A nosing is the part of a stair tread that projects beyond the face of the riser. Seen from above, the nosing overlaps the tread below. The word is also used for two other components: the hanging nib on the back of a roof tile, and a moulded strip on the outer fascia board of a gutter.
The stair nosing
The nosing enlarges the walking surface without lengthening the staircase. Your foot rests partly on it, while the going — the horizontal dimension of the tread itself — stays the same. A common projection is around 25 to 40 mm. On a steep stair a smaller nosing works better: a large overhang increases the chance of catching a heel on the way down. Beneath the nosing there is often a nosing batten closing the junction with the riser.
- Advantage: more foot room, easier and safer to use
- Drawback: trip risk if the nosing is too large, and a sharp arris damages quickly
- Finish: round the top edge or take the arris off. A non-slip strip or ribbed profile on the nosing is the cheapest safety measure on a slippery stair. Building regulations in many countries also require nosings on public stairs to be visually contrasting
The nib of a roof tile
On the underside of virtually every roof tile there is a projecting nib. It hooks over the batten and holds the tile in place. When tiling, every tile must actually drop with its nib behind the batten; a tile resting on top of the batten instead of hooking behind it will slide in a gale. Displaced tiles and moss growth are the first things to check when there is a leak near the ridge or the eaves.
The fascia moulding
The outer fascia board of a gutter sometimes carries a moulded strip, also called a nosing. It gives the gutter a finished edge and acts as a drip.
Points to watch
- Include the nosing when setting out the going and the clear headroom; do not confuse the nosing with the tread depth
- Do not repair a damaged nosing with filler — fit a glued solid timber strip to the tread instead
- When roofing, check the batten gauge against the tile; if the gauge is wrong, no nib seats properly
Related terms
- Nosing batten
- Stair string housing
- Stair tread
- Tread depth
- Overhanging stair tread
- Roof tiles
- Fascia board
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