Filling Gaps in Wood Floor?


    Anyone know if it’s OK to put wood filler between all the floor boards in a wood floor to close gaps? Various online sources say no, including Reader’s Digest. However, my floor guy who has ten years of experience says it’s fine.

    The supposed danger is cupping or boards popping out of place — or creation of worse gap problems — as the wood expands and contracts i the summer months.

    5 Replies

    1. Not sure which glue product as the flooring guys did that part. I would assume it’s one that has some flexability so that it does not crack.

    2. I think it depends on what you mean by wood filler. The stuff you get at the hardware store for filling nail holes won’t work well. But I have seen the method Northie describes used to very good effect – the only thing I don’t know is what type of binder is best to use with the sawdust. Some I know use an epoxy-based filler (but again, what kind?).

      Northie – what was the glue you used?

    3. I had lots of gaps between the original wide plank pine floors in my house, which I now use as my finished floor. This is what I did:

      I had the pine floors sanded and used the sawdust, mixed with a glue, to fill the gaps between the boards. The floors were further sanded, stained, and 3 coats of oil based poly were applied.

      In my situation, some of the gaps were quite significant – i.e. I could look down and see the top of the ceiling from the floor below. So prior to the sanding, I spent TONS of time cleaning out all the crud (dirt, nails, various unidentified objects) that was between the planks, and then used Great Stuff, in a VERY controlled manner, to create a base between the floor boards so that the sawdust/glue mixture would not fall thru, thus leaving a gap again.

      It’s been holding up for 3 years so far. In small sections where the sawdust/glue mixture has loosened, I used Bondo (the wood filler, not the all purpose putty <– can’t stain this one) to fill the gap. When it was wet, I applied the same color stain. Poly when dry and it’s done.

    4. I had wide board Oak floors on my Parlor and second floors. Some prior owner(s) had tried using wood filler, and it cracked, just as Dave says. It also looked really bad, so when it would come loose, I’d just toss it. Eventually I just left the cracks open.

    5. Originally they would have used horsehair or jute wound into a rope and oiled. Lots of historic houses now use natural rope stained to match the floor color. It allows for the expansion and contraction. ood filler will crack once it hardens with the expansion and contraction.

      I’m assuming these are wide board floors and not 3″ oak strips and that the “cracks” are fairly wide….1/8″ or more.