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Refinishing An Old Hardwood Floor

Question: I am a little confused about some aspects of floor finishing. I have heard the expression 'raise the grain' and I assumed that meant water swelling the wood fibers. I haven't had a problem with that so far but I'm not really sure if the problem would be now or later, or what it would be, and hope you will explain. A couple years ago I did an upstairs bedroom floor in this same house....another ancient and funky old floor. I used a water-based paint remover first (Back To Nature Multi-Strip) and had to use a lot of water to scrub off the residue, I mean a bucket of water and a scrub brush and pile of rags, just like if I was washing a kitchen floor. After that, I sanded and would use a wet sponge mop to remove the sawdust in order to see what my results were and if I needed to sand some more. I always let the wood get really dry before re-sanding. When done with all the sanding and wiping and re-sanding and the floor was bone dry, I used tack cloth to remove every last bit of dust. Then used a walnut stain, then urethane. That was two years ago and I haven't had any problem with that floor yet. What is the story about water swelling the wood fibers? I used a lot of water in doing that floor and I'm sure some of the wood fibers must have swollen at some point. So will that come back to haunt me in the future? So far all is smooth and shiny.

Answer: Raising the grain with soft woods is very common in furniture making. The problem with water on wood is multifold:

  1. It swells the wood, which can lead to buckling and twisting - especially if the wood has been laid very tight board against board.
  2. In furniture, the wood is generally open to air on one side - if you look at a dresser, the outside surface is finished with a sealer but the inside surface is not sealed, this allows any moisture to find an easy exit for evaporation.
  3. With flooring in newer homes, it is more than likely that the underside of the boards are laid on sheathing such as plywood or worse, particle board, which swells the instant it gets wet and does not shrink back when dry. In your case an older home, the boards are most likely the floors themselves and hence they are not "sealed" on the bottom allowing air to take care of any moisture problems that might develop. As well, when there is no airflow around the floorboards and they are damp, they will begin to rot. Water spilt on a carpet that has wood underneath, will feel dry to the touch after a period of time, but the water has penetrated the floor boards.
  4. If you used water and the boards are 100% dry, then you shouldn't have a problem. Most people don't wait for the boards to dry out completely. The surface water may have evaporated, but that does not mean that all the moisture that penetrated the wood has dissipated. If you seal a board that is wet inside, and there is nowhere for the water to escape, the board will begin to rot.
  5. Wood can only absorb so much water, if they are wet when you apply a water based stain it does not penetrate the boards to the depth it should.

Additional information on re-finishing hardwood floors.



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