Hardwood floors are a great choice for home flooring. Not only do they look good, they're easy to care for, resist wear and they're even eco-friendly. However, hardwood flooring does have one draw back, it can't stand up to prolonged exposure to water, so if water is allowed to stay on a hardwood floor the wood will be damaged (either stained or warped). Depending on the amount of water and how long it's been on the wood, the damage could be as slight as a small stain or so bad you will actually need to replace some boards. However, before you get into replacing boards, here's some ideas on how you can repair water damaged wood floors.
Start by drying the floor
If the water is just a puddle from someone's wet boots or a leak in the kitchen, first mop up the moisture then dry the floor as best you can. A fan or a hair dryer on a low setting will help dry both the surface and the subfloor under the hard wood. If you have access to the floor from below, applying heat from underneath will also help dry both the sub floor and the hardwood.
Removing water stains
If your hardwood floor dries with a white hazy film on the surface you might get rid of it using a soft cotton cloth and a very mild abrasive such as tooth paste, polishing compound or even tobacco ashes mixed with mineral oil. Gently rub the stained area until the haze is gone.
Unfortunately hardwood often dries with a very noticeable black stain. Sometimes the stain is just on the surface, but it could go all the way through the board in which case the stained board will need to be replaced.
Removing a black surface stain is a three step process
Mark out your work area with painter's tape then remove the surface finish starting with 60 or 80 grit sandpaper and finishing with 120 grit.
Next, mix oxalic acid crystals (available at home or hardware stores) with warm water, then carefully brush the mixture onto the stained area. Allow the solution to dry and if the stain is still there, repeat the application. The oxalic acid solution acts as a bleach to remove the dark stain, but if the stain persists after repeated applications your board is permanently stained and will need to be replaced.
Finally, refinish the area using wood stain to match the floor then seal the repaired area with polyurethane.
Flattening warped boards
A slightly warped hardwood board can often be flattened out by placing something heavy on it for a few days until the board loses its tendency to curl.
More badly warped boards may be flattened using a heavier object or your other alternative is to face nail the edge down, counter sinking the nail heads then filling the holes with color matching wood filler or a color stick.
If applying weight or face nailing can't get rid of the warp, you will need to remove and replace the damaged boards.