Refinishing during the season boards shrink and gaps develop

Q: I have 3-4-5 inch wide red oak floors installed over radiant heat. Each year when the heat is turned on the boards shrink and gaps between the boards develop. I am planing on refinishing the floors. How can I get rid of the seasonal gaps?

Will Timber Mate work as a solution for my problem? I would like to finish the floors with gloss finish.

A: The worrisome thing about this is: if you fill these gaps, what will happen when the floor expands? You may also face another issue if the floors are finished now. Polyurethane can seep between the boards, where, robbed of oxygen, it doesn’t really harden. then when the boards expand, this finish can get squeezed out and appear as poly balls on board edges. I think I would wait until spring or summer when they have closed up before sanding. Or, run a humidifier to get the RH up closer to 40%.

Follow-up Q: Thank you for your reply. Just a little more information: The floors were installed and finished in 1994, with a water base finish. When the floor was installed it was tight, with no seams or gaps. I was planning on sanding the floors with a random orbital sander, filling the gaps with Timbermate, then coating the floors with Waterlox, two coats of original sealer and two or three coats of the gloss finish.

A: You still have the expansion/contraction issue and I don’t think it would be wise to fill the floors under those conditions. Waterlox would be fine.