hardwood-floorhole
One weekend after a gathering, I noticed that there was a hole in my hardwood floor. The hole is about half an inch in depth and about the size of penny, maybe a bit larger. I know sometimes hardwood has pin knots, but this looks to be caused by a heavy step of a woman's high-heeled shoe.
What's the best way to fix this without having to tear up the floor?
I'd go with either a layer of cork or polyiso rigid foam. Then a floating floor on top. A nearby residential tower actually requires the cork underlay. The rigid foam will work just as well at lower cost.
The float floor can be two layers of ply staggered and screwed to each other, or a engineered hardwood product.
See also the "Sound Isolation Store" for great technical details.
It's likely a knot that came loose. The circular grain around it sure makes it look that way. The wood can turn blackish like this if water gets in there and sits which could easily have happened with a small hole like that.
How a Pin Knot is formed. Broken branch with encased dead twig, when the branch split under snow load, the twig slid through the surrounding wood, surviving intact. Same thing happens on tree trunks when small branches die and don't break off.
Best Answer
A solid healthy piece of oak would never collapse like that. You need to figure out what is going on before you fix it. Look at the underside if you can, break away any of the edges of the hole that come out easily (preferably without getting into the surrounding pieces) and try to figure out what you're dealing with. Look hard for moisture or evidence of insects. If you find anything suspicious, those problems must be dealt with first.
If ,however, the hole is pretty localized and the rest of the floor feels dry and solid, you can reasonably assume that it was an isolated defect in that piece and proceed with a patch. Here's a pretty decent tutorial on patching hardwood flooring:
https://www.youtube.com/watch?v=ez0GSSVuTyk
Good Luck!