What is a stair stringer?
A stair stringer, also called a string or stringboard, is one of the inclined, board-like members at the sides of a staircase that carries the treads and, where present, the risers. A typical stair has two strings, with the treads fitted between them. In Dutch it is called a trapboom.
Names
- Wall string: the string against the wall.
- Outer string: the string on the open side. On a spiral stair the central newel usually takes over this role.
- Carriage or centre stringer: an extra stringer under the middle of a wide stair to stop the treads from deflecting.
How the treads are fixed
- Closed (housed) string: grooves, called housings, are routed into the inside face of the string. Treads and risers slide into them and are fixed with glue and timber wedges from below.
- Cut (open) string: the top edge of the string is cut in a stepped profile and the treads sit on top. From the side you see the string as a sawtooth.
- Steel stairs: the stringers are often flat bar or sections with welded or bolted brackets for the treads.
Practical tips
- Squeaky stair: often a tread has worked loose in its housing. If the underside is open, re-glue and tap in the wedges, or glue timber blocks under the junction of tread and riser.
- Loose stringer: check that the wall string is properly fixed to the wall; without fixings the stair can spread.
- Alterations: never cut a piece out of a string for a pipe or opening. The string is the load-bearing part of the stair.
- New stair: allow for the thickness of the strings when measuring. They reduce the overall width, and the clear width between handrails is what counts.
Related terms
- Stair string housing
- Open string stair
- Stair riser
- Stair tread
- Walking line on a stair
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