How to Sand a Wood Staircase

Strip off old stain and varnish, if you're refinishing the staircase before sanding.

Sand flat stair treads with a handheld belt sander, fitted with a medium-fine grit belt. This is the only portion of the staircase where you can use a power sander, but don't use a large grit, and don't press the belt sander into the stair tread.

Sand only in the same direction as the wood grain to prevent cross grain scratches on the wood. Keep a belt sander moving constantly to prevent gouges.

Use a foam sanding block to hand-sand the flat portion of the treads along the edges and between the balusters.

Fold up sandpaper into a square to reach narrow spots that are too small for the sanding block. Also use the edge of folded sandpaper to sand crevices and ridges and between the stair tread and the stair riser.

Mold a foam sanding pad around the perimeter of stair balusters and sand up and down. The flexible foam hugs the baluster for smooth sanding.

Wrap a small piece of sandpaper around one or two fingertips, and rotate your fingers back and forth to sand the recessed crevices on balusters.

Sand the lip of stair treads and the entire stair risers with a foam sanding block.

Use a medium-fine grit to smooth the wood, and switch to a fine grit for a polished feel before painting or applying stain.

Finish-sand the entire staircase lightly with very fine, 400-grit sandpaper after the first coat of paint or the first coat of a finish coat, such as polyurethane or varnish. The first application can slightly raise the wood grain, making the surface feel a little rough.