Which joint along a staircase can you seal?

Walk the staircase before opening a cartridge

Look from below and again from the landing. Photograph the full run, not just the widest spot. The gap may taper to nothing halfway up. Walk normally and note movement; do not force a loose part to open the crack. Have a rocking tread or loose riser assessed by the installer.

Before opening the cartridge, try the Presch silicone gun in the tightest corner. Check you can turn your wrist and release pressure at the end of the run.

Choose the finish for each edge

At a stable stringer-to-wall joint, a compatible paintable acrylic may suit limited movement in a dry room. For a floating floor, find its installation drawing first. Preserve the expansion clearance unless the system permits an elastic joint there. Never use a finishing bead to glue a renovation tread to the wall.

At a stable, dry stringer-to-wall joint, trial OTTOSEAL A205 with the intended paint. It is not an adhesive for a moving tread.

Dry-fit before finishing

Look at a physical colour sample beside the floor in daylight and in the shadow beneath the first step. Try the profiling tool in the inside corner before dispensing. Protect the step from foot traffic while the approved joint cures. If access is tight, agree the order of work with the flooring installer and painter.

If the floor system explicitly allows an elastic joint at the foot of the stairs, compare the colour of OTTOSEAL S125 with a physical sample. This is a link to the sealant, not a colour chart.

Before opening the cartridge, try the FUGENFUX at the inside corner between the stringer and skirting. Choose the profile that fits without reducing contact at the edges.

Can I fill every gap between the treads?

Only where the stair design permits it. A widening gap, creaking joint or lifting tread needs investigation. At a floating floor the correct finish may be a trim that leaves the clearance free.