Refinishing renews worn hardwood for far less than replacement, and solid floors can be refinished several times over their life. It's labour-intensive and dusty, so know the scope before you start.
Recoat or full refinish?
If the finish is worn but the wood isn't damaged or stained through, a 'screen and recoat' — lightly abrading the surface and applying a fresh finish coat — refreshes it with far less work. Deep scratches, grey weathered wood, or stains call for a full sand-to-bare-wood refinish.
Sanding
A full refinish means sanding off the old finish with a drum or orbital sander in progressively finer grits, plus an edger for the perimeter. This is the hard, dusty part — go slow and keep the sander moving so you don't gouge or dish the floor.
Stain and finish
After sanding and thorough dust removal, stain if you want a different colour, then apply several coats of finish (oil or water-based polyurethane), abrading lightly between coats. Let it cure fully before heavy traffic and furniture — finishes keep hardening for days.