Acclimation of T&G Pine

[ellbaker]

My cabin is insulated and ready for 1x6 pine.  At least I thought it was ready . The indoor conditions are not what they will be when the cabin is lived in.  Summertime in Alabama is humid and the A/C is not installed. The interior relative humidty will be considerably lower once the A/C is up and running.  Will my pine walls shrink enough to be noticeable?  Do I wait for fall when the relative humidity is lower before I install the pine?

[ScottA]

I'm no expert but I'd allow the wood to sit inside the house for 6-8 weeks before installing it. I let mine sit for 6 weeks and it still wasn't really enough. It worked out OK but could have been better.

[rick91351]

I'm no expert but I'd allow the wood to sit inside the house for 6-8 weeks before installing it. I let mine sit for 6 weeks and it still wasn't really enough. It worked out OK but could have been better.

Good advise Scott.  However please be aware also that when the humidity increases so will the width of your boards.  It is surprising the amount of pressure they can exert.  Some one like Don_P needs to weigh in on this as far as spacing or how tight.  Where I am located if the humidity get way up to around 30% it is a disaster.  People us terms like muggy and damp.  I been down south - down south.  This is not muggy nor damp.  Sort of like an Idaho rain.  (Might be a half inch and people here are going nuts building arks and boats ....)     

[Don_P]

I prefer to let it acclimate with the heat on in the winter, that will probably be your lowest relative humidity and so the lowest equilibrium moisture content. For us the house bottoms out at around 40%rh or an emc of about 7-8%. We run an emc of about 14% now. For a 1x6 this translates to about a heavy 1/16" of shrinkage. I've never had trouble with subsequent swelling of well acclimated flooring or panelling unless it gets wetted by liquid water.
I did one section of our ceiling with fresh store bought t&g that I metered at 12%, there is some gappage. The other rooms I purchased the wood and waited into the winter, it is still dollar bill tight.

This is a link to the shrinkulator, a shrinkage calculator, there is good info on and linked to from that page on the wood/moisture relationship;
http://www.woodbin.com/calcs/shrinkulator.htm

This is a pdf from the forest products labs giving average emc for various locations by month. It will give you a baseline for current conditions;
http://www.fpl.fs.fed.us/documnts/fplrn/fplrn268.pdf

This is a short wiki on emc... notice the graph, at "normal" temperatures rh is the prime mover, temp plays a much more minor role. Heat it up to kiln temps and that changes but for acclimation keep an eye on the rh.
http://en.wikipedia.org/wiki/Equilibrium_moisture_content
http://en.wikipedia.org/wiki/Equilibrium_moisture_content

[rick91351]

Thanks Don_P Interesting, I figured you would see way more movement that than after the boards become acclimatized.  But that stands to reason. 

We imported a container of hand crafted rosewood furniture for partial resale, partial private orders several years ago.  I have a rose wood executive desk from that order and one solid panel split almost a quarter inch I never have gotten around to repairing that but now you mention it the size has remained the same.  I just figured that it was because from our very low humidity.   

[ellbaker]

I bought a moisture meter and most of the wood was around 8-10%. I couldn't help myself and put some up in the foyer.  I then read where wood exposed to outdoor air will have an emc of 14% in Alabama. I plugged all of the numbers in the calculator posted by Don P. My wall should expand by over an inch.  Hope it doesn't buckle too bad    I am now focusing on the exterior and getting the power hooked up to get the A/C and heat running. Installing the remaining pine will be a good winter job.  Wish I would have thought of this earlier because 3000 sq ft of pine takes up a lot of room in my future kitchen and living room.

[Don_P]

Install it now. When I've gotten flooring in that condition in the south we've skipped acclimation and put it in, I've never had it buckle and if you look at my emc it is the same right now. You stay around that value year round. If you look at the numbers for oak you'll see that I should have run into an even greater buckling danger than with your pine, yet I haven't. The best I've come up with is the ability to take some compression and hysterisis, the wood will approach but not hit theoretical emc, ~2-3%, from either direction. And we've just hit my limits .

Your pic just came up, looks like eastern white pine.

[ellbaker]

Yes it is Eastern White Pine.  

So you think it is best to install now?  It will be Friday until I can get to it again. If the moisture increases, should I wait until I can get the house conditioned?  I thought the foyer would be a test and I wouldn't have much to replace if it started buckling.

[TheWire]

T & G Pine can shrink slightly and the tongue slides within the groove.  There is a bit more of the tongue that is exposed.  If the finish is natural, this isn't usually noticed.  However, if you stain the boards a darker color after you put them up and the boards shrink, there is a good chance of seeing thin stripes of un-stained wood as more of the tongue is exposed.  I always stain my T & G prior to putting it up and make sure to stain the tongue also.  BTW, I use a linseed oil finish thats available in multiple colors.  Brush or roller it on, wait 10 minutes, wipe it off, then in a couple hours its dry, stained, sealed and ready to install.  Its called Velvit Oil

[Don_P]

Good point from TW about prefinishing, I can't tell if you have but we typically do all sides prior to installing. Yes I would go ahead and install it unless it crosses above about 12%, this was my cutoff line when recieving wood for a cabinet shop and worked pretty well.

We have a running debate in our house between the velvit/ watco type finishes and the slightly glossier harder drying wiping oil finishes like waterlox. I prefer the latter, my wife the former. Occassionally at high humidity I have wiped mold from the flatter finishes on lower parts of doors, etc where humidity has condensed on the finish.

[ellbaker]

I was planning to put it up on the walls unfinished and then spray Polycrylic Satin with a HVLP sprayer, 2 coats.  I planned to prefinish the ceiling boards before installation.  I was not planning to put finish on the backside. I thought that the cellulose insulation would minimize air infiltration and therefore minimize moisture issues. Polycrlyic is $40 a gallon and one coat on the back side is approximately 6 gallons.   I am now questioning that decision based on the feed back from this thread.  

Are the wiping oil finishes more difficult to apply?  

[Don_P]

EWP is probably one of the most forgiving woods as far as dimensional stability is concerned. A balanced finish helps prevent uneven moisture absorption but this is a pretty stable wood, the risk of cupping is probably pretty low. The sprayer will be faster and a nicer finish but will consume more material due to overspray. Do lightly buff between coats if at all possible. I like the oil finishes because even I can do a decent job with it.

when blind nailing if you crawl back onto the tongue slightly with the nail rather than putting it right at the base of the tongue to V joint it will allow a little movement room before you expose a nailhead.