How to Install a Stair Skirt Board to Existing Stairs

Hold a level plumb on the topmost stair tread and form a vertical line on the wall, 2 to 3 inches above the stair. Move down the stairway and repeat the process on the lowermost tread, or the part of the stairs you step onto when ascending or descending the stairway.

Extend a chalk line on the wall between the upper and lower marks along the stairway. Pull the chalk line along the middle and extend it as far away from the wall as possible. Release the line so it snaps on the wall, forming a diagonal chalk line that runs the length of the stairway, 2 to 3 inches above each stair tread.

Hold a piece of printer paper on the wall against the topmost stair tread. Position this paper to set flush against the small triangle wallboard. Secure this paper in place with masking tape. Also, trace the outline of the bullnose tread on the paper. Cut excess paper off along the edges so its top falls flush with the chalk line. Repeat this process of securing a paper template on the wallboards adjacent to each stair.

Remove the paper template from the wall, being careful not to separate the individual pieces taped to each other. Lay the template on the 1-by-10-inch skirt board stock. Trace the outline with pencil before removing the template. Cut around the outline using a circular saw.

Set the skirting board against the stairway wall, sliding it flush over the treads. Secure the skirting to the wall studs using 2-inch screws.

Scoop wood putty using a putty knife and apply it over the screw heads until covered. Allow the putty to cure for the time specified on the manufacturer’s directions before sanding it lightly until flush with the surrounding surface.