Wood floorboards can soak up moisture and expand. Since wood boards are butted together, expansion causes the centre sections along the length of the boards either to bow upward or cup downward. This bowing results in an uneven floor that is difficult to clean, and too much expansion can cause some boards to split down the middle. If the damage is not severe, individual floorboards can be replaced, and high spots can be sanded down.
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Things you need
- Space heaters
- Wax crayon or paint
- Nail set
- Straight edge
- Two-part epoxy adhesive
- Rubber mallet
- Plastic buckets
- Various grade industrial sanding discs
- Three-pad orbital floor sanding machine
- Vacuum cleaner
- Heavy-duty hand-held orbital sander
- Finishing nails
- Wood filler
- Urethane varnish or floor wax
Mop up any standing water and allow enough time for the floor to dry out. You may have to place space heaters in the room and open the windows for a day or two.
After the floor has dried, have a flooring expert test the moisture level in the floorboards with an electronic moisture meter. Once the moisture level is reduced to the acceptable level, proceed with your repairs.
Inspect each plank for signs of splitting. Minor surface cracks are acceptable, but if the floor gives under pressure, mark the suspect board(s) for replacement with a wax crayon or a dab of paint.
Sink any exposed flooring nails below the surface with a nail set and hammer. If you find any loose nails, replace them with the next size up.
Mark two lines along the length of the split board 1/2 inch in from both edges with a straight edge and pencil. Make lengthwise cuts through both marks with a jigsaw. Stop the cut 1/2 inch from the ends of the board; this prevents damage to the hidden tongue-and-groove joints along the edges of adjacent planks.
Cut through the ends with a hammer and chisel, and remove the centre section of the damaged board with a pry bar. Pry out the remaining waste from the adjacent tongue and grooves with a thin chisel. Try not to damage adjacent planks.
Make a shallow cut through the lower lip of the U-shaped groove on the replacement board. Remove the bottom section of the groove so the remaining upper section can be lowered onto the tongue protruding from the adjacent board. Repeat and remove the lower section of the short groove on one end of the replacement board. Slide the lengthwise tongue of the replacement board into the groove on the neighbouring board to test the fit, but do not lower the board all the way at this stage.
Mix a batch of two-part epoxy adhesive by following the instructions on the package. Coat all relevant mating surfaces of both the replacement plank and the neighbouring boards with a liberal amount of adhesive.
Insert the tongue of the replacement board into its matching groove on the neighbouring plank. Slide the end tongue of the replacement board home and tap the seams down with a rubber mallet. Wipe off excess epoxy with a rag soaked in warm water.
Place plastic buckets filled with water on the board to weigh down the board. Let the epoxy cure overnight.
Carefully remove all baseboard and shoe moulding from the perimeter walls by prying them loose with a pry bar.
Fit 36-grit sanding discs to a rented three-pad orbital floor sanding machine. Sand the floor even by starting at one end and working your way along the length of the floor, going with the wood grain. Keep the machine moving at all times to prevent the discs from digging in. Use a semicircular sweeping motion as you work your way along the floor. Do not try to remove too much material during each pass.
Vacuum the floor between passes to prevent sawdust from clogging the sanding discs. Fit new discs as soon as the old discs become worn. Complete as many passes as necessary before changing to finer-grade discs. Aim for a uniform colour across the floor. Finish hard-to-reach corners with a heavy-duty hand-held orbital sander.
Change to progressively finer-grade sanding discs once the floor has an even look and no remaining dark patches. Work your way up from 50-grit to 100-grit discs to remove sanding swirl marks left by the 36-grit discs. Go over the floor with at least three passes between grade changes.
Damp mop the floor and let it dry overnight before making your final pass; this raises any remaining loose wood fibres and results in a smooth floor after final sanding.
Replace the skirting board and shoe moulding by attaching them to the wall with finish nails and a hammer. Sink the heads below the surface with a nail set, then fill the holes with matching wood filler.
Finish the floor by coating it with urethane varnish or flooring wax.
Tips and warnings
- Hang a sheet of plastic over the doors to keep sawdust from invading the rest of the house. Place an outward blowing box van in a window opening the help ventilate the room during sanding.
- Wear safety goggles, ear protection, a respirator and heavy boots during the sanding operation.
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