Caulking Gaps Between Plank Floor Boards?

[David Stone]

I've got wide plank flooring.  In the winter, the boards shrink and I have gaps between the planks.  Most are small, but some gaps are about 1/4".  I'm getting a lot of cold air coming up from the basement.
It looks as if someone put some caulking between the planks and on the underside.
I've checked at Home Depot, a local supply store and a contractor, and no one has heard of caulking between plank floors.
One suggestion was to cut rigid foam insulation and fit it between the beams, but there are some areas I cant reach, and there are a lot of wires I'd have to deal with.

Any ideas on how to address this?  Here are some photos showing the little gaps.  I can fit a putty knife in these.

[dlorenz]

How about sprayed-in foam insulation?

[Kansas City Fireslayer]

I'd guess that's probably wood filler instead of caulk. A trick hardwood flooring guys use is to cut long strips of "wedges" with a 7 degree bevel on edge. Use 3/4" thickness, or whatever thickness your floors are, and orient the grain. Add glue to the strips so they stay put. Pound them in tight but not to the point of spreading boards. Add some weight on top if you feel it needs it. Of course you'd have to dig out the old stuff first. A multi tool like the Fein would make quick work of it. These will most likely be proud of the floors level so this is best used when sanding and refinishing.

Although time consuming, you could lay blue tape on each side of the wedge and bring down the wedge height with sharp hand tools. You would then have to add some dye to some shellac for a color match touch up. Maybe a little polyurethane on top of that afterwards. Some practice pieces for an aged color match would be in order.

I had to add some wedges to my white oak floor refinishing job and even I have a hard time finding them today. I did resand the whole floor though. I'm confident it could be carefully done without sanding....Just more time consuming.

I forgot to add that you could add some soft color matched putty to the small areas around the wedges that don't fill to your liking. You can still clear coat over the putty. Minwax has many colors at the BORG.

[MsNomer]

Compression cracks are caused not allowing room for expansion. Use caulk.

[Roly]

Compression cracks are caused not allowing room for expansion. Use caulk.

I agree.  Clean out what you can and apply a dark colored flexible caulk since the floor expands and contracts. with the seasons.    Roly

[petertay15]

We have the same floor, same problem. I cut long 1/8 wide strips of wood (3/4 depth) which I pressed in the cracks topside. And, yes, every crack had to be scraped clean of hard hundred-year-old dirt. I didn't think of tapering the strips. If the crack was wide, two strips got pressed in. Polyurethane was brushed over the strips to sort of glue them in place (and wiped off the adjoining boards). Underside was sprayed with foam before we put up a false ceiling made of cottage siding 3/8 x 4 inch boards. LOTS of work, but the old barn is now a beautiful guest house.

[petertay15]

I should have mentioned in my previous reply that we had tried water putty in a different building, but it broke up and started breaking out after two seasons.
Also we tried Big Stretch caulk in a small area to see it it would stay in place. Yes it does, still okay after four years, but we didn't pursue that idea because it looks a bit gummy.

[Kansas City Fireslayer]

These look like cracks between boards and not within a board, correct? If so, I would still use wedged strips glued in place. Caulk would be a quick cheap solution, IMO. Unless you clear coat any caulk it will eventually darken with dust and dirt since it stays somewhat "grabby". If I opted for a caulk I'd make sure it was compatible with a topcoat. I guess it depends on how picky you want to be and how much time you want to spend on it.

A glued in strip will still allow your floor to expand and contract without buckling the floor if space was allowed at the width of the floor border (think under your baseboards). You could also try gorilla glue in the larger ones with the wedges. It will foam a bit and possibly help seal things up better. I wouldn't go overboard with it or it will come out at the top.

[mad_planter]

If those boards are still expanding in the summer time from humidity and you fill those cracks very much instead of being able to expand into the empty space between them they will buckle and pull loose from the floor.

[blackhat]

Insulate, draft seal and vapour barrier the basement.