How to Replace Mortised Stair Treads

Locate the nails that hold the baluster in place. The location depends on the type of staircase. In many cases you will need to use a 1/2-inch putty knife to pry off the stair tread's mortised end. Use a nail extractor to remove any nails you come across.

Insert a 7-inch pry bar underneath the stair tread. Use the pry bar to pull the stair tread's front edge off the stair rise. If the stair tread seems stuck, look underneath the staircase to see if the tread is screwed in place. If it is, back out the screws with a drill and Phillips driving bit. Pull the old stair tread out from underneath the next stair rise and remove it from the staircase.

Set the old stair tread on top of a new stair tread. Use the old stair tread as a template to determine the correct length and depth and to trace around the mortise. If your tread had a mortised end, remember to include that as part of the template.

Cut out the new stair tread's mortise with a jigsaw. Cut the tread to the appropriate length and depth with a table saw or circular saw with a fine-tooth cutting blade.

Run a bead of wood glue along the stair rise's upper edge. Set the new tread into place over the stair rise and press it into the glue. Either drive finishing nails through the tread's front edge or go back underneath the staircase and replace the screws you had removed in Step 2.

Set the baluster's bottom edge into the mortised area. Line up the top edge underneath the stair railing. Use finishing nails to secure the baluster in place. If your stair tread has a mortised end, glue this piece into place next to the baluster.