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deercula
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# Posted: 20 Nov 2017 11:32am - Edited by: deercula
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My cabin is now a year old. I've noticed that the tongue and groove knotty pine on the interior walls is shrinking. Some of the fasteners in the tongue are now visible. You need to look close to see them because they blend in with all the knots. The shrinkage is not showing at all in the length. The butt joints are still tight. The tongues are about 1/4 inch and are still inside the grooves. Seem to have shrunk about 1/8 th. inch. Questions: How long will the pine continue to shrink? Would another coat of polycrylic help?
https://i.imgur.com/XK9iNQW.jpg
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creeky
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# Posted: 20 Nov 2017 11:39am
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that might actually be seasonal?
winter comes, humidity levels drop. Wood shrinks. It might reswell in the summer.
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justins7
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# Posted: 20 Nov 2017 04:41pm
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I think it may continue to shrink. My recently purchased cabin is 25 years old and there are gaps on every piece of wood (tongue and groove walls). Originally I thought it was just shoddy workmanship but now I think it's due to long-term shrinkage. Some gaps are as much as 1/4" (!) but generally it's about 1/8". I believe wood continues to dry over the course of decades, and then fluctuates during seasons.
But I'm no expert...
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Steve_S
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# Posted: 20 Nov 2017 05:30pm
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All wood will shrink & expand as humidity varies, pine can be a bit worse than others but better than many others. Monitor the humidity in your place and that should tell you a lot. I also have scads of 5/8 thick T&G Pine throughout which was kiln dried, while it does expand & shrink a little it's not as bad as some pieces that I have which were not kiln dried, they seem to be subject to more shrinkage & expansion. I think that kiln dried & milled reduces the sap & moisture to start with which helps. I do recall reading about that somewhere a while back.
Top-coating with Poly could help BUT I would wait till it's good & dry and shrunk, not something to do when the wood has absorbed moisture from the humidity. If you already have something on the wood like Shellac or other stain make sure what your top coating with won't have a bad effect... IE never put Poly over Shellac ! unless you wanna sound the worst drunken sailor cussing in every language he's ever heard. I used almost ALL shellac except in washroom & kitchen areas and when I needed am extra piece for the kitchen I took a piece of scrap which was shellac'd and put poly... (I prefinished everything before I installed) and what a mess...
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ICC
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# Posted: 20 Nov 2017 06:37pm
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Quoting: Steve_S IE never put Poly over Shellac !
Partly true. There is shellac and there is de-waxed shellac. Note, the wax in std. shellac is a natural component so if the can does not say de-waxed it still has the wax. Guess which one you can overcoat with poly or whatever you want? Yep, de-waxed.
Wood does shrink and expand across the grain much more than length. Length expansion is usually negligible. When installing T&G with the intent on staining I always stain and apply the first coat of clear finish on the boards before installation. That way the shrinkage is much less noticeable.
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rayyy
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# Posted: 20 Nov 2017 06:46pm
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Having the same problem buddy. I can't believe them boards would dry out and shrink that much! Life living in a log cabin,go figure!
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Cowracer
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# Posted: 21 Nov 2017 10:50am - Edited by: Cowracer
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Wait till humid summer. They will grow back to normal.
It will practically frighten you how much wood expands and contracts over the year. I made one mistake on my floor and cut a piece too short. The trim barley covered the board in the summer, but there is a good 3/8 gap during the winter.
However, I have t&g pine walls in my cabin and see hardly no change in the gaps from summer to winter. All I did was 2 coats of Zinsler Amber Shellac on 'em. I wouldnt think that shellac would have that much effect, but I cant think of any other reason.
tim
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Borrego
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# Posted: 21 Nov 2017 09:58pm
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My tongue and groove that I used for flooring at my desert cabin has shrunk waay more than that....and it ain't gonna come back...I need to fill the bevels with an epoxy or somethin'..... I don't know....
So i don't have an answer, but good luck! Maybe some kinda marine resin epoxy stuff?
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ICC
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# Posted: 21 Nov 2017 11:08pm
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A problem arises with things like pine, spruce, etc T&G lumber. Most of that has too high a moisture content the way it comes. It is kiln dried the same as construction lumber and then after it leaves the mill who knows what happens. The forest service has a publication called Drying and Control of Moisture Content and Dimensional Changes. Use Google if you want to read up. It lists optimal moisture content for interior uses in many places for every month of the year. If possible it is beneficial to choose the driest month and let the wood sit for a couple weeks before installing. It may be of interest to note that hardwoods are dried to a lower moisture content in the hardwood mill. A moisture meter is an indispensable tool when working with moisture critical things. You can get a DIY serviceable model for $30-40. The pros use ones that cost 10X as much. I have a mid range Lignomat from about 25 years ago. Use it on everything from checking siding before painting to furniture wood.
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Steve_S
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# Posted: 22 Nov 2017 07:19am
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Like Cowracer, I used 2 coats of Zinsser Shellac on the majority with the two exception (kitchen / bath). Plainly states on can NOT to top with Poly. There are other brands of shellac's out there so who knows.
REF Link:
https://www.rustoleum.com/product-catalog/consumer-brands/zinsser/interior-wood-finis hes/bulls-eye-shellac
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toyota_mdt_tech
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# Posted: 22 Nov 2017 08:59am
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Isnt this somewhat normal? And why its grooved so you dont see the insulation? through the cracks? If it expanded, I suppose it could buckle. So some floating and shrinking/expanding will occur. Maybe treat it like hardwood floors, leave it in the space a few weeks before install to get it acclimated.
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Fanman
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# Posted: 6 Jan 2019 06:00pm
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Quoting: Steve_S Like Cowracer, I used 2 coats of Zinsser Shellac on the majority with the two exception (kitchen / bath). Plainly states on can NOT to top with Poly. There are other brands of shellac's out there so who knows.
If you want to topcoat over shellac, use Zinser's "sanding sealer", which is dewaxed shellac.
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Atlincabin
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# Posted: 6 Jan 2019 07:37pm
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Too much shrinkage is the result of the poor quality wood we get nowadays. Very little of it is kiln dried the way it was maybe 50 years ago. Best thing to do is let it sit for a couple of years before installation, but not too many folks have the time to do that. One thing that will help, if you're still in the planning stage, is using narrower boards (1x6 rather than 1x8 or 1x10). Shrinkage percentage will be the same but the absolute amount of shrinkage per board will be less. And the shrinkage will be less noticeable.
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Wilbour
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# Posted: 6 Jan 2019 08:44pm
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Shrinkage when it's cold... yup I get it.
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Aklogcabin
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# Posted: 7 Jan 2019 12:12pm
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I was in the woodworking business for 11 years. When you purchase t g wood. Always buy any wood to be used at least 2 weeks before you plan on installing it. Let it set it in your home , cabin. The moisture in the wood has to stabilize to the moisture content in your home. How long that takes depends on how wet the wood is. Top coats work to try to help moisture from moving into the wood. Moisture causes wood movement. Polyurethane is more resistant to moisture transfer that shellack. But cuts should be done on an angle. 15 degrees is what i do.
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