Measure the dimensions of your steps. Find the depth of the step from the nose to the back riser and the width of the step. The standard tread is 10 inches deep and 3 1/2-feet wide by 1 inch thick. Cut the wood into these measurements with a saw.
Cut risers from 1/4-inch hardwood sheets. Again, measure your existing steps for the proper measurements. Cut one riser for every new tread.
Cut the nose from the existing stair treads using a circular saw. Clean up the edges with a chisel and an electric sander fit with 120-grit sandpaper so it is flush with the riser on the step.
Finish the treads and the risers with the same color and finish of polyurethane varnish. Take them outside to a work area over a tarp to catch any drips. Use a fine-paint brush to coat them evenly on the top side only. Dry according to the manufacturer’s directions. Sand lightly with 0000-grade steel wool and coat with one or two more layers. Dry thoroughly for two or three days so the coating cures to a hard finish.
Place the first riser at the top of the stairs just under the flooring from the landing. Cover the back with a zigzag coating of construction adhesive and press in place. Sink a few finishing nails into the top of the riser with a hammer to hold it place. There will be a gap at the bottom.
Set the first riser in place after coating the back with a zigzag of construction adhesive. Press it firmly against under the edge of the riser.
Work down the stairs, adding a riser and then a tread until you have covered the stairs with the new wood. Allow the adhesive to dry for at least 12 hours before light traffic and 48 hours before regular foot traffic.