Filling gap beneath hardwood floor (between floorboard and foundation)

Question

There's a sizeable gap between the edge of hardwood flooring and the foundation by this fireplace:

You can see that the wooden base the strip of floor was nailed too ends about inch early:

As a result, many of the nails in the strip were justing stick out into space and the board is one bad step away from cracking in half. My first impulse is to cut shove a 2x1 in the gap so the board won't hang over the edge. Is there any reason not to do this? Is there a special kind of wood I'd want to use to avoid termite / other problems in the future?

Answer 1

That's a good solution if you can hammer the wood piece in tight enough and below the bottom of the flooring.

Also you could pour in a floor leveler to the same height as the existing floor. Once it's cured cut a strip of flooring so that there is a 3/8 inch gap between the piece and the fireplace apron. Glue it down with a construction adhesive.

You could also remove the trim pieces that frame the apron. Install wider trim pieces to cover the gap (leaving room for expansion). Apply colored caulking to fill expansion gap.