How do I caulk the seams/in an 1859's yellow pine 5" floor? It is not tongue-in-groove.?

Question

We discovered beautiful pine floors under our carpeting in our 1850's mill house. We have re-finished, sanded, and polyurethaned them, but they are not tongue-in-groove, and are open to the bsmt, which has some mold. My wife is allergic, and we don't need dirt raining down into the bsmt, or mold coming up.

Answer 1

The most effective method would be to take up the planking, lay a plywood sub-floor, paper, then re-lay the planks. Then you could insulate from below for added warmth and energy efficiency.

An added (but labor-intensive) procedure would be to groove both edges of each plank (router) and use separate (maybe oak) tongues to tighten and strengthen the floor.

Answer 2

Easy answer...you don't.

Caulking the joint won't do much good because the joint will continue to expand and contract and the caullk will just fall through leaving you with the same problem.

More involved answer....try roping the seams

Traditionally the way to fix the holes that develop in wood floors was to rope them. Using wood glue and small finish nails attach the to the boards stuffing it into the joint until it becomes level with the floor or sunken just a little bit. Stain to match the floor and poly over it. The rope will be able to contract and expand with the floor better than caulk and will look more like the wood flooring throughout it's life. This solution too is really only temporary and will eventually fail....5-10 years typically.

Another solution would be to use a 3/4" plywood infill below the floor to act as a type of subfloor and then rope the joints. The possible problem with this method is you have new wood (although fairly stable because it is plywood) against old wood. They have different moisture contents and could move in different directions causing more problems down the road.

As for your mold issue, guess what...it's already travelled beyond the basement. Get rid of the moisture in the basement or it will keep growing and move into your walls if it hasn't already. To see how much mold you have either hire a home inspector who does mold testing or get a self-test from Home Depot and follow the instructions carefully so as not to taint the results