A staircase is two jobs in one. The parts you walk on (treads, nosings, handrail) take wear every day and want a hard timber. The parts nobody touches (strings, risers, newels you plan to paint) only need to be straight, stable and cheap enough to paint. Most good domestic stairs mix the two, and the decision that matters is which timber goes where.
The other decision is legal. A new or altered stair in a house has to meet the Building Regulations, and the numbers are fixed, so work them out on paper before you choose timber.
Timber choices for stairs
Four timbers do most of the work, with hemlock as the usual paint-grade alternative to pine.
| Timber | What to know |
|---|---|
| Oak | The default for hardwearing treads, handrails and newels you want to see. European oak is hard enough for daily traffic and takes stain and finish well. It reacts with iron, especially when damp, leaving dark marks, so use stainless or coated fixings. The European oak page has more. |
| Ash | Pale, tough and harder than European oak on the standard Janka test. It works cleanly, stains well and bends well, which suits shaped handrails. It’s a perishable timber outdoors, which doesn’t matter on an indoor stair. See the ash page. |
| Sapele | A moderately hard red-brown hardwood often used for handrails and stair parts. The interlocked grain gives the striped figure but can tear out when planed or moulded, so ask for parts that are already machined and sanded if you can. The sapele page covers it. |
| Pine (redwood) | Scots pine, sold in the UK as redwood when imported. It’s easy to work and finishes well, but it’s soft (about half the hardness of oak), so treads dent and wear. It’s the usual choice for strings, risers and paint-grade parts, and for a stair that will be carpeted. See the redwood page. |
Beech is as hard as ash and turns well, so you’ll see it in spindles and handrails, but it moves a lot with changes in moisture, so it wants stable indoor conditions. See the beech page. Hemlock is a light, clear softwood used for paint-grade spindles, handrails and newels. It’s about as soft as pine, so it’s for parts you hold and paint, not parts you stand on.
Hardwearing treads, paint-grade strings
The usual pattern is hardwood where feet and hands go and softwood everywhere else:
- Treads and nosings: oak or ash if they’ll be left visible. Pine is fine under carpet or a runner.
- Handrail: oak, ash, sapele or beech if it’s to be oiled or lacquered; hemlock or pine if it’s to be painted.
- Strings and risers: pine or MDF if painted.
- Spindles: match the handrail if they’re clear-finished; hemlock or pine if painted.
When you ask a yard or joiner, say which parts will be painted and which will be clear-finished. That changes the grade they’ll offer, because clear-finished parts need to be free of the knots and resin that paint would hide.
Cladding an existing stair with oak
Cladding (capping) means fixing new hardwood treads and risers over the old softwood ones, keeping the structure. It gets you an oak stair without rebuilding, but the extra thickness catches people out.
Every step goes up by the thickness of the new tread, but the floors at the top and bottom don’t. So the bottom step gets taller and the top step gets shorter by the same amount, while every rise in between stays the same. Approved Document K says the rise and going should be consistent throughout a flight, and an odd step at the top or bottom is exactly where people trip. Before you buy, work out what your new top and bottom rises will be. If new flooring is going down at the same time, its thickness may balance it out.
Also check:
- the new nosing projection, so the going doesn’t shrink;
- the gap between the handrail and the new tread surface, which drops by the tread thickness.
The rules for a stair in a house
In England, the guidance is Approved Document K (2013 edition). For a private stair (one serving a single dwelling):
- Rise: between 150 and 220 mm per step.
- Going: between 220 and 300 mm.
- Pitch: no steeper than 42 degrees.
- 2R + G: twice the rise plus the going between 550 and 700 mm.
- Consistency: rise and going the same throughout a flight, with level treads.
- Headroom: at least 2 m, with a reduced allowance for loft conversions where 2 m won’t fit.
- Handrail: top of the rail 900 to 1000 mm above the pitch line, and on both sides if the stair is 1 m wide or more.
- Guarding: needed where the drop is more than 600 mm, 900 mm high on a house stair, and in a building that may be used by children under five, a 100 mm sphere must not pass through any opening. Avoid horizontal rails children can climb.
- Open risers: allowed if treads overlap by at least 16 mm and a 100 mm sphere can’t pass through the gap.
These are summaries. The full document covers winders, landings and doors, so read it or ask building control before you draw anything. This guidance applies in England; Wales, Scotland and Northern Ireland have their own.
Building control
A new staircase, or moving an existing one, needs Building Regulations approval. A like-for-like replacement is generally treated as a repair, but one that’s only similar, not identical, needs approval. Your local council’s building control team, or a registered building control approver, can tell you which applies before you start. Stair strings, trimmers and the opening in the floor are structural, so get any new structural sizes checked rather than guessing.
Finishes and slip resistance
A clear-finished hardwood tread can be slippery in socks. Some floor oils come in anti-slip versions tested to the R9 to R11 slip classes. These are sold for floors, so check with the manufacturer that the product suits stairs, and don’t overload the coat, because a thick film can be more slippery. A carpet runner is the other option on a steep or busy stair.
Sources
- GOV.UK, Approved Document K: protection from falling, collision and impact (rise, going, pitch, 2R+G, consistency, headroom and loft relaxation, handrail height and both sides at 1 m, guarding height and 600 mm drop, 100 mm sphere, open risers 16 mm overlap)
- Planning Portal, Part K (2013 edition is current, England)
- Oldham Council, Staircases (new or relocated stairs need approval; exact replacement is a repair)
- Forest Research, Scots pine timber market study (imported Scots pine is sold as redwood)
- The Wood Database, European ash (hardness, working, staining, bending; with the oak, beech, sapele, hemlock and Scots pine pages for comparative hardness, movement, iron staining and tearout)
- Richard Burbidge, Hemlock spindle (via SpecifiedBy) (hemlock as a light, clear softwood for stair parts)
- Osmo UK, Polyx-Oil Anti-Slip (R9 and R11 slip classes, floor use, thin coats)
