Gaps between some boards

Q: I have hardwood installed throughout my home (maple 3 inch). Lately, I noticed some gaps between some boards. Maybe 1/8 inch or less. I have air exchanger installed. What could be the cause of these gapping?

Our home is 1-1/2 years old.

A: The humidity levels are too low. A common problem in winter. In cold climates, I would try to keep the RH in the home near 40% RH.

Gapping at the ends of boards

Similar Q: Unfinished oak flooring was installed in our home a few years ago. Sanded and finished on site. It now shows cracks at the end of boards (not down the side). Is this from a lack of humidity?

A: Difficult to say, because wood flooring usually expands and contracts side to side, across the width of the floor. Though in the case of quarter sawn, it expands and contracts up and down. Shrinkage and hence gapping does indicate a lower moisture content in the wood compared to when it was first installed. If the shrinkage is more severe the top coat finish may stretch and fracture making the gap more obvious.

Wood was harboring excessive moisture before it was installed

Q imported from our old site, Face Lift Floors: We moved into our new home in mid-September 2002. three quarters of our first floor (approx 3300 square feet) is covered with lovely stained white oak flooring with the beveled edges. Our contractor installed it and it was stained, sanded and finished with Glitza on site. By mid-November in a very mild midwest (near Chicago) winter there were huge cracks in the bottom of the bevel between the planks.

The floor guys took a look at it and said it was due to dry conditions and the cracks would disappear with moisture. Our contractor then found that the “April air” wasn’t wired to the furnace, and fixed that. But we have large cracks even in our master bath where we have a steam shower and there is a lot of constant moisture. Now after 3 months of humidity control & moisture on the insides of my windows the cracks are even worse. I can see the subfloor through some of them.

Question: Is moisture the only cause of these cracks or might there be some other causes we should consider, and what are the best ways to take care of this problem? Our contractor is great but our home is too new and too top-notch to have this sort of problem!”

A: When you say “huge” cracks have appeared at the bottom of the bevel, how wide of a crack do you mean? If you can see the subfloor through some of them, then you are talking 1/8 or larger. Are these deep bevels, as opposed to micro bevel which usually appears on factory-finished floors? I ask this because if it is a micro bevel, then if the floor is sanded and refinished, you usually will lose the beveled edge, and it becomes easier to fill the cracks. Humidity or lack thereof really is the culprit in expansion and contraction of wood floors.

It sounds to me that this wood was holding excessive moisture even before it was installed. It probably should have been delivered to the site about a week before the job started, assuming of course, that the subfloor and all other major sources of moisture in a new home have all cured and dried out (painting, pouring new concrete in the basement, etc.) Use of a moisture meter in such cases can help determine if the wood is within 7-9% moisture levels before installing it. If the moisture in the flooring is above this level, then sometime after installation, as it begins to stabilize, excessive shrinkage will occur.

This floor will likely have to be resanded and the cracks filled. Perhaps waiting until mid-summer, when humidity is greatest will show how much the gaps will close up. I don’t expect much satisfaction in this case, however. Especially if you now have decent climate control in your house.

I would also like to make a comment about Glitza, which I have used numerous times in the distant past. It is certainly a very very tough finish. It is also highly toxic, both when applying it and afterward. It emits urea formaldehyde vapors, even when sanding it off. Truly nasty stuff. I don’t even think it is available in Canada anymore.

I’m sure you are disappointed with what has happened to your floors, and I am equally sure the wood was harboring excessive moisture before it was installed. That explains the excessive shrinkage. If it was within normal limits of moisture content, and then installed in an unacceptably high humidity area, the boards would have expanded and cupped from the pressure of one board pressing against the next.

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