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paulz
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# Posted: 13 Jul 2018 11:58pm
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I'm reading that a board will be at it's widest in summer, because hot air holds more moisture. But what about a soaking wet deck board in winter, won't that absorb more moisture?
Btw, here is an online estimater
http://owic.oregonstate.edu/wood-shrinkswell-estimator/mobile
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rockies
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# Posted: 14 Jul 2018 06:12pm
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It will probably absorb a certain amount and reach a point of equilibrium. The best thing is not to fasten it down so that it can't move at all, which will only split the board eventually around the screw heads.
The best method is to use those slot fasteners that go between the boards and you screw down through them into the deck joist. Then the boards can move a bit.
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paulz
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# Posted: 14 Jul 2018 06:28pm
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You read my mind Rockies. I'm finally ready to fasten down my deck boards, which are 12-14" wide, and I'm worried that being that wide, the screws will inhibit movement. Probably why deck boards are normally much narrower. Those screws you mention sound perfect, now to find them. Thanks!
Testing a 1/2" gap, figuring 1/4" swell come winter.
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darren
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# Posted: 14 Jul 2018 10:37pm
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My brother-in-law studied wood expansion/contraction in school, and he's told me repeatedly that the amount that wood expands and contracts is so minor that it's barely worth thinking about.
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ICC
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# Posted: 14 Jul 2018 11:44pm - Edited by: ICC
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Quoting: darren the amount that wood expands and contracts is so minor that it's barely worth thinking about.
I guess that may be a matter of opinion or how one defines "much" movement, or what the project is. Depending on species and how the board is sawn, (radial cut or tangential cut, for example), a 12" wide board can expand or shrink 1/16 to 1/4" across the width. It is proportional, if a 12" wide shrinks 1/4 then a 6" wide will shrink 1/8". For many things that is a lot, other things it may not be noticed or at least not a big concern. If the wood is green or freshly treated PT, the movement can be much greater. I've had fresh felled and sawn pine shrink 3/4" over a 12" width from green to dry.
Wood that is wet from a heavy rain is not really a fair comparison to wood that is just exposed to high humidity. Very broadly stated, the MC , moisture content of wood in a 30 to 50% rel humidity will be about 6 to 10 percent. Wood laying flat and being rained on could easily get to a much higher MC.
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rockies
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# Posted: 15 Jul 2018 05:46pm
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Here are some different options. You will probably need ones that will require that you to cut a biscuit slot in the side of each board over the spot where the joist is.
https://www.strongtie.com/hiddendeckfasteners_screwsandnails/ebty_premium/p/eb-ty-pre mium-hidden-deck-fasteners
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Cowracer
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# Posted: 16 Jul 2018 10:49am
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Quoting: darren My brother-in-law studied wood expansion/contraction in school, and he's told me repeatedly that the amount that wood expands and contracts is so minor that it's barely worth thinking about.
My cabin is all knotty pine T&G. I have yet to notice any 'gaps' in the boards (either at the T&G edge, or where two ends butt together) or bowing through 3 cold dry winters and 3 murderously humid, hot summers. We only stay at in on the weekends, and we leave everything off when not there, so it basically varies temps and humidity inside when we are not there.
I gotta agree that changing humidity seems like a non-issue. Now... wood outside will continuously loose moisture over years. You can butt two deck boards together and in a few years there will be a gap between them. Short of submerging them for months, you will not get enough moisture in them to prevent this.
Tim
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acamelo
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# Posted: 17 Jul 2018 11:37am - Edited by: acamelo
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I'm building a cabin 20x24 with 10x20 porch and have all my concrete footing pads level in place ( 3 rows of 18). I now need to determine correct elevation of 6x6 blocks for each pad. I would like to have about 2 feet under the cabin for access. I have never used a laser level and not sure the best way to approach this. After my blocks are set to correct height I will then run 3 - 2x10 beams down the building and then subfloor. Any feedback would be much be much appreciated. Thanks
Anthony
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acamelo
Member
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# Posted: 17 Jul 2018 02:42pm
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I'm building a cabin 20x24 with 10x20 porch and have all my concrete footing pads level in place ( 3 rows of 18). I now need to determine correct elevation of 6x6 blocks for each pad. I would like to have about 2 feet under the cabin for access. I have never used a laser level and not sure the best way to approach this. After my blocks are set to correct height I will then run 3 - 2x10 beams down the building and then subfloor. Any feedback would be much be much appreciated. Thanks
Anthony
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Borrego
Member
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# Posted: 18 Jul 2018 03:34pm
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Quoting: darren My brother-in-law studied wood expansion/contraction in school, and he's told me repeatedly that the amount that wood expands and contracts is so minor that it's barely worth thinking about.
He ought to come out to our desert place........a couple years will turn a 2x 6 into a 2x5.....
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Wendigolake
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# Posted: 23 Jul 2018 07:12pm
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I am using T&G Pine in my cottage in Northern Ontario. Been several years now and I have not noticed any expansion or contraction issues. My cottage is unheated in the winter time. I do think that the fact it was kiln dried before I installed helped.
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Riv
Member
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# Posted: 31 Mar 2021 06:29am
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Hi
I'm curious how your floor turned out?
thanks
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