How to Refinish Hardwood Floors

Refinishing hardwood floors is one of the highest-payoff renovations you can do — it can make 20-year-old flooring look new for a fraction of replacement cost — but it's also one of the least forgiving DIY projects on this list. A drum sander removes wood fast, and an uneven pass leaves a dip that's visible under any raking light for the life of the floor. This guide covers the full sand-stain-seal process, but if your floors have deep water damage, structural cupping, or you're nervous about the drum sander, a full refinish is a reasonable one to hire out.

Budget a full weekend to a full week depending on room size and dry times: a day of sanding, a day for staining (if used), and 2–3 days of polyurethane coats with drying time between each. Skill level is intermediate to advanced — start in a closet or low-visibility room to get a feel for the sander before tackling the living room.

Materials, Tools, and Cost

DIY refinishing runs roughly $500–$1,000 in rental equipment and supplies for an average whole-floor job, versus $1,100–$2,663 (and $3–$8 per sq ft) for a professional crew — the labor savings is substantial, which is why this remains a popular DIY project despite the difficulty. If your existing finish is only worn, not gouged or cupped, a lighter "screening" (buff and recoat) job runs $1.00–$2.50 per sq ft in materials and skips the drum sander entirely — always check whether you actually need a full sand before committing to one.

Shopping list:

• Drum sander rental ($70–$100/day) plus edger, and ideally an orbital finish sander — full equipment rental for one day often runs $150–$200
• Sandpaper in a full grit sequence: 36 or 40 grit (coarse, for finish and old stain removal), 60 grit, 80–100 grit (final smoothing pass)
• Wood filler for gouges and gaps between boards
• Tack cloths and a shop vac for dust removal between grits
• Stain, if changing or refreshing color (oil-based penetrates deeper; water-based dries faster and off-gasses less)
• Polyurethane topcoat — oil-based is more durable and ambers slightly; water-based dries clear and fast but needs more coats
• Natural-bristle or foam applicator pads, painter's tape, respirator mask, kneepads

Prep: Before the Sander Ever Touches the Floor

1. Clear the room completely and remove shoe molding/quarter-round along the baseboards — sanding under it is impossible and it hides the transition anyway.
2. Set every protruding nail or staple below the surface with a nail set — a sander drum will shred its own sandpaper (and possibly gouge the floor) on an exposed nail head.
3. Fill large gouges and gaps with wood filler matched to species, and let it cure fully before sanding — sanding wet filler smears it across the boards.
4. Seal the room off from the rest of the house with plastic sheeting over doorways; drum sanding produces enormous amounts of fine dust that travels through HVAC ducts if you don't isolate it.
5. Test in an inconspicuous area — inside a closet or under a rug — to dial in sander pressure and grit before working the main floor.

Sanding: The Step That Can't Be Undone

1. Start with the coarsest grit (36–40) on the drum sander, running with the grain, and never let the drum sit still while spinning — a stationary sander cuts a trench in seconds. Keep the sander moving in overlapping passes, tilting it up at the end of each pass before reversing direction.
2. Sand the perimeter and corners with the edger, which reaches where the drum sander can't — blend the edger passes into the drum-sanded field so there's no visible line between the two.
3. Vacuum thoroughly between each grit. Leftover coarse-grit dust gets dragged by the next finer grit and causes scratches you'll only notice after staining.
4. Progress through the full grit sequence (36/40 → 60 → 80–100) — skipping grits leaves sanding marks that only show up once stain or finish highlights them.
5. Finish with a final buff using a floor buffer and fine screen, then tack-cloth the entire floor to remove all dust before staining or sealing.

Staining and Sealing

1. Apply stain with the grain using a rag, brush, or foam applicator, working in manageable sections and wiping excess before it dries tacky — uneven wipe timing is the #1 cause of blotchy stain.
2. Let stain dry fully per the label, typically 24 hours, before topcoat — coating over wet stain traps solvent and causes a cloudy, soft finish.
3. Apply the first polyurethane coat thin and even with a lambswool applicator, working with the grain and maintaining a wet edge just like painting a wall.
4. Lightly screen-sand between coats (220-grit or a fine screen) once each coat is dry to the touch, then tack-cloth again — this is what gives the final coat that glass-smooth feel.
5. Apply 2–3 coats total, with full cure time (check the label — often 24 hours between coats, and several days before furniture goes back) before walking normally on the floor.

Finishing Touches

• Wait the full cure time — usually 3–7 days — before moving furniture back, and use felt pads under every leg even after that.
• Avoid rugs with rubber backing for the first few weeks; uncured finish can react with rubber and leave a permanent mark.
• Reinstall shoe molding once the finish is fully cured, nailing into the baseboard, not the floor, so the floor can still expand and contract seasonally.
• Keep leftover stain and finish, labeled, for future touch-ups — an exact match years later is much easier with the original can in hand.

Done carefully, a full sand-and-refinish should last 10–15 years before it needs doing again, longer if you stick to felt pads and routine cleaning rather than harsh chemical cleaners. It's a genuinely demanding project — but it's also one of the few where the "before" and "after" photos alone justify the sore knees.