A broken stair tread is hazardous because we often don't look at steps as we climb them. Replace a broken step right away. The difficulty of this job depends on

the construction of your staircase and the accessibility of the underside. It's better to replace a damaged tread than to repair it. A patch could create an irregular step that surprises someone unfamiliar with it.

How to Replace a Broken Stair Tread:

 Carefully remove any decorative elements attached to the tread. Pull up carpeting and roll it aside. Remove trim pieces on or around the edges of the tread. Remove the balusters by detaching the top ends from the railing and separating the joints in the tread. Some staircases have a decorative hardwood cap inlaid into each tread. Remove these with a flat pry bar, taking care to pry from underneath the cap to avoid marring the exposed edges.

If possible, hammer upward from underneath the stairs to separate the tread from the risers and stringers. Otherwise, use a hammer and pry bar to work the tread loose, pulling nails as you go. Once the tread is removed, scrape the exposed edges of the stringers to remove old glue and wood fragments.

Measure the length for the new tread and mark it with a combination square so the cut end will be square and straight. If the tread has a milled end for an inlay, cut from the plain end. Cut the new tread to size, using a circular saw, and test-fit it carefully.

Apply a bead of construction adhesive to the exposed tops of the stringers. The adhesive will strengthen the bond between the tread and stringer and will cushion the joint, preventing the parts from squeaking.

Set the tread in place. If you have access to the step from underneath, secure the tread to the riser above it by driving screws through the riser into the back edge of the tread. To fasten it from the top side, drill and countersink pilot holes and drive two or three screws through the tread into the top edge of each stringer. Also drive a few screws along the front edge of the tread into the riser below it. Fill the screw holes in the tread with wood putty or plugs.

Reinstall any decorative elements, using finish nails. Set the nails with a nail set. Reinstall the balusters, if necessary.