Hardwood Dado Rails

External corners are mitred at 45 degrees; internal corners are best scribed, cutting the second length to the profile of the first so an out-of-square wall cannot open the joint. Join lengths along a straight run with a 45 degree scarf rather than a butt joint — it stays invisible when the timber moves.

Run the rail parallel to the string, measuring the same vertical height above the nosing of each tread so the line stays true to the stairs rather than to the floor below. The mitres where the raking rail meets the level runs are compound cuts: take the angle off the actual pitch with a sliding bevel and cut a test piece before committing a full length.

Traditionally about a third of the wall height, which lands near 90cm from the floor in most houses. Hold a length against the wall with the furniture in place before fixing anything — the right height answers to the room and the skirting below it more than to any rule.

A dado rail is a horizontal moulding fixed part-way up a wall, originally to stop chair backs marking the plaster — which is why it is also called a chair rail. It still does that job in a dining room or hallway, and it gives a tall room a break that stops the walls reading as one flat expanse.