affects of contraction/swelling of pine floor on face nailing/varnishing

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Forum topic by johnee posted 08-09-2012 01:39 AM 1270 views 0 times favorited 4 replies Add to Favorites Watch
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3 posts in 2115 days

08-09-2012 01:39 AM

I live in Vermont where winters are very dry and summers can get very humid.

I installed 7” wide eastern knotty white pine flooring in a room around February, very dry. I let it sit in my house for a month before installing, but i guess that wasn’t good enough because during installation, the boards were pressed very tight together, but a week after installation (normal t/g install, nailed in tongue), the dry conditions caused some shrinkage, and some gaps showed up. They weren’t very serious, but they were noticeable. I liked that look actually cause it gave it the aged look i’m trying to achieve.

I haven’t sanded/finished the floor yet, I had to save the money for sander/varnish, AND for weather where i can open the windows to vent the VOCs.

Anyway, now that it’s summer, I wanted to finish it. However, due to the humidity, the floor is tight as a drum, NO gaps. I have questions regarding this drastic expansion with respect to face nailing/varnishing.

Here are my questions :

1. I want to face nail the boards. I’m concerned about the relatively drastic swell/contraction of the wood and how face nailing will affect that. If i face nail now, will the boards warp or otherwise twist about when they dry out this winter? Should I wait until it dries out a bit?

2. Same basic question about varnishing. If I varnish now, will it get screwed up when humidity goes to 10% in winter? Should I wait to varnish until it’s dried a bit? I will be using Waterlox varnish.


4 replies so far

View Sawkerf's profile


1730 posts in 3067 days

#1 posted 08-09-2012 02:12 AM

If you think it through, you’ve already answered your question. Nailng through the tongue allows that board to move (expand/contract) away from (or toward) the nailed edge. If you face nail on the groove side, the board will still try to move but can’t. It will either bow or split.

-- Adversity doesn't build reveals it.

View Jorge G.'s profile

Jorge G.

1537 posts in 2473 days

#2 posted 08-09-2012 02:27 AM

What is underneath the floor? If it is concrete, did you place a vapor barrier? How far apart are tied strips?

Your floor should not move so much, and the varnish should in fact help keep it relatively constant in humidity if you placed a vapor barrier underneath.

-- To surrender a dream leaves life as it is — and not as it could be.

View johnee's profile


3 posts in 2115 days

#3 posted 08-09-2012 03:00 AM

this pine floor is on the second level of house, on 3/4 plywood. I used some vinyl tiles to raise the low spots (a large spot in center of subfloor) and then put down a few layers of resin paper to smooth the whole thing out.

Sawkerf, I understand what you’re saying; I didn’t think about the lateral freedom of movement afforded by the tongue nails.

I also thought about reduced moisture flow once the varnish was on. Pine will allow relatively deep oil absorption, and since the main vector of moisture is from the face (vs. subfloor), I was hoping the wood would be sealed enough to prevent future expansion/contraction, but just don’t have that experience.

View johnee's profile


3 posts in 2115 days

#4 posted 08-09-2012 01:39 PM

fyi, I don’t have to face nail, just wanted the look.

I think my plan will be to wait a bit until the moisture level goes down to a midpoint between summer and winter.

Then, I’ll drill holes just about the same size as the nails, maybe even drill countersink-holes for the heads so they wont have any real bite into the wood, then sand and varnish.

I’m guessing the reduced moisture flow into the wood and room to wiggle around the nails should prevent any damage.

what do you think?

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