A staircase squeak comes from a tread that has worked slightly loose from the stringer or the riser beneath it, so wood rubs against wood every time weight shifts across it. It sounds like a bigger problem than it is, and in most cases it does not need the stairs opened up, just access from one side and about twenty minutes.
Working from below, if you have access
If there is an open staircase from underneath, in a basement for example, this is the easier fix, since you can see and reach the exact spot that moves.
- Have someone walk slowly across the stairs above while you watch and listen from underneath.
- Feel along the joint between the tread and the riser for the exact point where it flexes or a gap opens as weight passes over it.
- Run a bead of construction adhesive into that gap.
- Drive a screw up through the riser into the tread at a slight angle, positioned to miss the screws already there.
- Repeat on any other treads that moved during the walk-through, since a squeak is rarely limited to just one.
Working from above
Without underneath access, the fix has to go through the top of the tread itself, which means the finish matters as much as the fix.
- Locate the exact board or seam that squeaks by walking across it slowly in sock feet.
- Drill a pilot hole angled down through the tread into the stringer or riser below.
- Drive a trim screw through the pilot hole, deep enough to bite into solid wood but not so deep it splits the top surface.
- Countersink the screw head slightly below the surface.
- Fill the hole with matching wood filler or a wood plug, sanded flush once dry.
Talcum powder or graphite as a quick test
Before drilling anything, it is worth confirming the noise is really friction between two dry wood surfaces and not something structural. Work a small amount of talcum powder or powdered graphite into the seam where the squeak happens, using a straw or a folded card to get it right into the gap, then walk across it again. If that quiets the noise down, at least temporarily, it confirms the diagnosis and tells you exactly where to aim the screw. If the powder makes no difference at all, look more closely before drilling, since the movement may be coming from further along the stringer than the sound suggests.
When it is more than one stair
A single squeaky tread is normal wear, and either fix above deals with it permanently in a few minutes. A staircase where every tread squeaks, or where treads visibly flex or bounce under weight rather than just making noise, points to a wider problem with how the stringers were originally fastened to the floor framing at the top and bottom of the run. That is worth having looked at properly rather than screwed down one tread at a time, since something else in the structure may be moving that a single screw through one board will not fix.
If more than one or two treads move, or the stringers themselves look like the real issue, it is worth having a carpenter inspect the staircase in Kitchener, Waterloo or Cambridge rather than chasing the same squeak every few months.