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Curing creaky stairs – working from underneath

We’ve already looked at how to fix creaky stairs if you don’t have access to the underside of the staircase in a previous article. If the underside of your stairs is exposed (for instance, if you have a cupboard under the stairs in the hallway) or the soffit panel is easily removable, then you can achieve a much better and more lasting repair.

It’s best if you can get someone to help you by walking slowly up the stairs, counting them off as they go so that you know which step they’re on. Make a mark on the ones that creak, then have your assistant test the creaky ones so that you can find out which joints are loose.

There are two main problems that are likely to be the cause of any creaks: loose housing joints and loose blocks.

Loose housing joints

The treads and risers of a staircase are generally held in place in the string housing by using wedges. If any of these has worked loose, it’s a straightforward fix in most cases; just prise out the wedge using a chisel, clean it up with glass paper, coat it with PVA wood adhesive and knock the wedge back into place with a mallet.

If the wedge is split or damaged, you’ll need to make a new wedge to replace it. Use hardwood for this – softwood will get squashed, and then you’ll be left with a creaky step again.

Loose blocks

The interior angle of the joints between the treads and risers are usually supported by triangular blocks glued into position. If any of these have come loose, remove them altogether and sand off the old adhesive from the blocks and the joints with glass paper.

Before replacing the blocks, prise the joint open slightly using a chisel, then squirt PVA wood adhesive inside. Then go to the upper side of the staircase and tighten up the joint using countersunk screws as described in our earlier article.

Returning below the stairs, apply PVA to the holding surfaces of the blocks, then rub-joint them into the angle of the joint. If necessary, fix them into place using panel pins while the adhesive sets. (The panel pins are additional to the adhesive, not an alternative.)

If any of the blocks are missing, they’re easy to replace if you have a suitable workbench and vice. Set a length of 50mm x 50mm (2″ x 2″) softwood on end in the vice, then cut the wood from corner to corner across the end, down the length of the wood. Cut the two resulting triangular sections of wood into 75mm (3″) blocks.