Filling gaps between softwood floor boards

I want to paint the softwood floors in my old house. They are in rough shape but until the rest of the house in renovation I won't be doing anything with the floors. Until then I just want to give them a coat of paint to look good. But the boards have shrunk over the many years and I am thinking of filling in between the boards before painting. I am hoping to find a substance that is non-toxic to people and pets, paintable, and somewhat flexable (as the boards do move slighty, and expand and contract depending on the weather). Any recommendataion?

Thanks,
Terry
Halifax, Nova Scotia, CANADA

 

Terry, in Halifax myself and running into the same problem. Have you managed to find anything that works? Considered using thin foam tubing in the large gaps (some of them are over 1/4", then covering with wood filler, but haven't had chance to try it out yet.

 

It is not recommended that gaps between boards be filled. Due to expansion and contraction of boards, the movement tends to cause fillers to pop out.

 

Cannot say that I agree with the previous post. Certainly, it is not advisable to use something that will restrict movement, but afterall, if you used pine or fir splints, in these gaps, then this wood is soft enough to undergo slight changes in width.

I too am interested in a good answer to this issue. One option I have tried is simply indoor caulking. It dries quick yet is still able to adjust to expansion and contraction. Takes a bloody eon to install from tubes though. I used the dark brown on my pine floors and it looks better than the gaps that were previously evident.

Must be another easier to manage and install compound that retains some elasticity.