Squeaky stairs can have a certain charisma. They can alert one to an unwanted intruder or a late night teenage adventure. Often times they are simply a source of irritation or more importantly squeaks and creaks are an indicator that the stair needs repair. A staircase that needs repair is an unsafe stair. The squeaks are caused by the movement of wood rubbing against wood. Maybe the glue has aged and lost it’s adhesion. Older stairs were commonly just fastened with nails and with the expansion and contraction that happens with wood, over time the nails loose their grip and start to slip as stepping pressure is applied.. Squeaks are usually easy to repair especially if one has access to the undercarrage.
The first step is to locate where the squeak is coming from. Is it the front of a step or the back? Is it where the tread/step hits the stringer or wall?
Squeaks from the front of the step: If the squeak is in the front of the step, is there cove mold between the tread and riser under the nose? If so the cove might be able to be pulled off and some glue added and pin nails refixed. If a crack is visible under the tread at the riser one could glue and insert a wood shim or two for a bond (make sure to only snug the wedge in, not to force it and tweek the step). The shim can be trimmed flush with a utility knife. If one is real handy or a carpenter is involved one can drive a few trim head screws (very small heads that will sink into the wood and accept putty) from the step into the riser but the stair finish will be comprimised a bit. If the undercarrage of the stair is accessable then little blocks of wood (glue blocks) can be used where glue would be applied onto two adjacent sides and pushed up into the step/riser joint. This is the proper way to secure a step to a riser when the stair is first fabricated. If the blocks are there and the glue has worn maybe a few well placed short screws or nails can be applied to resecure. Make sure to check the size of the nail/screw so it doesn’t break out the riser or step face.
Squeaks from the back of the step: If the squeak is coming from the back of the step it should be repaired from the undercarrage. On older stairs the risers were simply nailed to the back of the treads. These nails need to be helped by a few well placed screws and the problem will be solved. If there is enough separation between the riser and tread I’d squeeze some glue into the joint before fasteners are used.
Squeaks from the step to stringer/wall. These squeeks can be arrested from on top of the stair but a repair from the undercarrage will leave the finished look of the stairs unscarred. From the top of the tread/step a well placed screw or two toescrewed (angled) from the step into the skirt board or wall should stop a squeek (if the repair screw is going directly into sheetrock or plaster an internal stud should be located first). From the undercarrage one can see if the stair has been fabricated with the ‘housed and wedged’ method of stairbuilding. If so, and a wedge is visable the original glue has apparently worn out. Try and take the wedge out and reglue and drive it home with a hammer. If there is simply glue or nailing blocks there, they need to be rescrewed, again being careful not to run a screw up through the face of the tread.