Installation and Fixing of Wooden Stair Treads with Risers

The process is much the same with or without risers. Risers add one extra stage and more careful fitting.

1. Measuring every step separately. Concrete stairs almost never have identical steps or true right angles. The joiner measures the height, depth, flatness and moisture of the base on each step.
2. Making or adjusting the parts to size. Treads are cut to the real shape of the staircase, not to the drawings. Riser heights are adjusted to even out small differences in the concrete.
3. Preparing the base. The concrete is cleaned of dust and grease and primed. Larger bumps and dips are levelled with a smoothing compound or ground down.
4. Fitting risers and treads. The parts are bonded with a flexible adhesive made for joining timber to concrete, usually polyurethane or MS polymer based. Depending on the base, hidden mechanical fixings are added. Each step is checked with a spirit level after fitting and weighted down until the adhesive sets.
5. Finishing the details. Gaps along the wall are covered with a trim or flexible sealant, small joints are filled, and if the treads did not come pre-finished, they get lacquer or oil.

On a steel staircase, a resilient pad goes between the timber and the metal. It stops vibration passing into the wood and keeps the steps from knocking.

There are two similar jobs: fitting wooden treads on their own, and fitting treads with risers. The difference is what stays visible.

• Treads only: timber goes on the horizontal surface only. The concrete step fronts need a different finish, such as plaster, skim coat or paint. This option is simpler and quicker.
• Treads with risers: the vertical faces are clad in timber as well, so the staircase looks like one piece. It takes more measuring and fitting, because the joint between tread and riser is easy to see and must not show a gap.

Why do people choose risers? They hide uneven concrete fronts, protect them from shoe scuffs and kicks, and are easier to keep clean. Families with small children also like that there is nowhere for a foot to slip into. Risers can be the same timber as the treads, a contrasting wood, or painted MDF that matches white doors and frames.

Stairs need hardwood. Oak is the usual choice, followed by beech and ash. Oak resists wear well and has a strong grain. Beech is a little softer and reacts more to moisture.

• Solid treads, from one piece or glued lamellas, can be sanded and refinished several times over the years.
• Engineered treads, built from several layers, hold their shape better and twist less, so they suit wide steps.

Treads are usually around 30 to 40 mm thick, and risers are thinner. A thicker tread is stiffer and can be sanded more often, but it also raises every step. For the surface you can choose lacquer, which forms a hard-wearing layer, oil, which keeps the natural look, or hardwax oil as a middle way. On stairs it is worth thinking about slip resistance too, either in the finish or as grooves near the front edge.

The simplest case is a straight staircase with flat, dry concrete and steps of roughly equal size. These things add time and cost:

• Uneven or damaged concrete that needs levelling and edge repairs
• Removing old tiles, vinyl or existing treads
• Winding or turning stairs, where every step has a different shape
• Risers, rounded nosings and joining up with an existing balustrade
• Recessed LED lighting or aluminium nosing profiles

One detail that is often forgotten: the timber raises each step by the thickness of the tread. The first step from the floor and the last one at the top will come out different unless the floor build-up is planned with this in mind. All steps should be the same height. Building regulations generally require this, and uneven steps are a real trip hazard.

Replacing the surface of existing stairs is normal finishing work. If you plan to change the staircase structure itself, check with your local building authority first. In a block of flats, always agree any work in shared areas with the building management or owners' association beforehand.

Most problems do not show straight away, but after a few months or after the first heating season.

• Damp or dusty base. The adhesive does not grip across the whole surface, hollow spots form under the tread and the step starts to creak.
• Timber not acclimatised. Treads should rest for a few days in the room where they will be fitted. The air there should be at roughly 40 to 60 % relative humidity, and fitting should wait until plaster and screed are dry.
• Rigid or general-purpose adhesive. Timber moves, and if the bond is not flexible, it cracks or lets go.
• No gap at the wall. Timber expands with moisture. With nowhere to go, the tread lifts or splits.
• Careless measuring. Your foot notices a difference of a few millimetres between steps, and people trip on such stairs.

When the work is handed over, walk the stairs up and down, slowly and at normal pace, and check:

• No step creaks, flexes or moves underfoot
• All steps are the same height, including the first and the last
• The tread overhangs the riser by the same amount on every step
• Treads are level and the front edges line up
• There is no visible gap between tread and riser
• A gap is left at the walls and covered with trim or sealant
• The finish is even, with no runs or missed spots
• You have been told when the stairs can take full use and how to care for the surface