There’s a gap in my kitchen hardwood floor. Only a single board exhibits the problem. Not sure what’s causing it. Any suggestions for fixing it?
Cause: maybe there was a machining flaw in one of the boards that prevented them from mating tightly, or the wood shrunk, or the floor installer was hung over. Hard to say.
Solution: none (unless you want to pull up the floorboards and reinstall them). Don't try to fill the crack with wood putty - it'll wind up looking even worse. You'll just have to learn to live with it. Gaps in wood floors are pretty common, and yours really isn't that bad.
One or two of the flooring boards has shrunk in width since the time of installation of the hardwood floor. There is not too much that can be done to really fix it.
I have heard that one technique for #2 above is to remove an less noticable piece of flooring from some edge of the room to use as the patch. Then replace new over by the edge. The patch can then inherit the look, color and finish of the original floor.