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Small Cabin Forum / Cabin Construction / Plywood Floor Exposed
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cspot
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# Posted: 10 Feb 2017 11:11pm
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Been doing some planning on the cabin and had a question since this will be built over several weekends or planning to possibly use some vacations.

I plan on using 3/4 T&G on the floor. How long can I leave it exposed while getting the walls and roof on? Would a few weeks hurt? Would painting it be better? Other options?

Ontario lakeside
Member
# Posted: 10 Feb 2017 11:34pm
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we built our place over two summers. the floor platforms were completed the first summer and one half of the building (its basically to cabins with a short hall.) the decking for the second half was protected with a tarp but got very wet a few times. after it was dried in we let the floor dry completely and had almost no issues. Sight swelling at the joints but it did not require any attention before we played the finished floor. Hope this helps.

razmichael
Member
# Posted: 11 Feb 2017 07:55am
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Mine was exposed for a week or so but during the period we had some wicked rain storms. I got some really cheap oil paint (the stuff the stores sell cheap because it was returned) and also taped the seams with tuk tape. My major concern was that I has insulation under it. Might have been overkill but seemed to do the trick.

cspot
Member
# Posted: 11 Feb 2017 10:08am
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I was going to wait until later to insulate underneath as I don't want to run the risk of the insulation getting wet. Sounds like I will be ok leaving it exposed for a few weeks.

ShabinNo5
Member
# Posted: 11 Feb 2017 12:31pm
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During our build we used 3/4" plywood that was treated. We also covered the surface with poly tarps between weekends. After 3 months we were dried in. No problems.

bldginsp
Member
# Posted: 11 Feb 2017 02:53pm
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I've seen many new houses get soaking wet before they were dried in. It's never a problem so long as it's not for many weeks, and so long as you use plywood, not OSB.

I've only seen a few buildings where plywood was damaged by water from exposure. These were left exposed through several sets of storms. Plywood seems to hold up well through a few cyclings of wet/dry but eventually it will delaminate. Once dry it holds its original dimensions.

OSB is different. In the process of making it the fibers are crushed and compacted with great pressure. When it gets wet, the compacted fibers swell up and once dry they don't go back to the original dimension. OSB can take one light rain, but no more.

You are wise to wait to insulate. I built my subfloor joists, covered it with old roofing, left it for two years before I could frame it up. When the time came, we insulated and framed to the roof ASAP, no rain in between.

I considered insulating, then painting heavily to seal it and covering with plastic. But that's a lot of extra work and money, if you can avoid it so much the better.

MtnDon
Member
# Posted: 11 Feb 2017 06:01pm
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See if you can find Advantech in your area. It is unbeatable for subflooring that may be exposed to weather a while.

cspot
Member
# Posted: 11 Feb 2017 06:28pm
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Thanks MtnDon. I just checked the nearest Lowe's to camp and they have it in stock. Price isn't bad either.

Bret
Member
# Posted: 11 Feb 2017 08:42pm
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MtnDon is right about the Advantech. On our build, the subfloor was exposed for many months and water would just bead up on it. Glue and screw it down. I was also able to use a sherman williams product on it, amorseal, and it is a great floor finish.

So my subfloor became my finished floor for about $.66 cents per square foot.

toyota_mdt_tech
Member
# Posted: 11 Feb 2017 09:26pm - Edited by: toyota_mdt_tech
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I used no OSB, only genuine plywood. I made it illegal to have OSB even on my property.

While the plywood floors was exposed, we had about 6 massive rain storms roll over in the 9 days it took me to get the dried in shell, plywood was soaking wet but dried right out. Caution, if you dont want the wood stained, remove all nails from floor. The vinyl sinkers from the nail gun even left black marks on the floor along with a 7 1/4" skil saw blade also left a black mark on the wood.

No harm to the plywood.

bldginsp
Member
# Posted: 11 Feb 2017 10:25pm - Edited by: bldginsp
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Use hot dipped galvanized nails if you are concerned about staining.

I have two junk pieces of plywood that I've left out for years, covering other junk. One is OSB. It was 1/2" to begin with, now it's 1". The piece of 3/8 plywood is still 3/8 and not delaminating, good enough for a,dog house or chicken coop.

I assume everyone knows we are talking about exterior grades only.

The Advantech is an OSB but apparently formulated not to suffer from water like the regular stuff. A quick search shows it comparable in price to ply.

The only other thing to consider with glued composites is that they have a LOT more glue in them than plywood, if the issue of off-gassing is important to you.

MtnDon
Member
# Posted: 11 Feb 2017 10:53pm
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Advantech performs better than plywood subfloor according to a carpenter I know who has decades of home building experience.

bldginsp
Member
# Posted: 12 Feb 2017 12:41am - Edited by: bldginsp
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OSB is stronger than plywood by all test metrics. I don't like it cause I know what happens when it gets wet. It's the least expensive so they use it on re-roofs to cover skip sheathing. But roof sheathing is what inevitably gets wet around the edges. Plywood can survive a degree of this, OSB cannot. Gonna be a lot of screwed up roofs in 20 years.

Advantech appears to be the next logical step in OSB development. The glues they use now have less toxins to off gas than in the past, but toxins are toxins. Toxins on roof OSB are less likely to get in your house, from floor OSB it's already in your house. Aside from that Advantech appears to be a superior material at a similar price.

I'll still stick with plywood. It's good enough, and that's as much as I need. The Egyptians made plywood that lasted 3000 years, they didn't make OSB.

toyota_mdt_tech
Member
# Posted: 12 Feb 2017 11:12am
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Quoting: bldginsp
I'll still stick with plywood. It's good enough, and that's as much as I need. The Egyptians made plywood that lasted 3000 years, they didn't make OSB.


The smell when you walk into new construction with OSB vs plywood only is no comparison. One smells like a wood working shop, other smells like a glue factory. I'm with bldginsp on this one.

bldginsp
Member
# Posted: 12 Feb 2017 12:59pm
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That's true Toyota. I love the smell of plywood in the morning, it smells like- accomplishment.

One other thing about OSB and the other composites is that they are extremely efficient in terms of wood use. They literally use the garbage that falls off from all other lumber milling operations to make it, whereas before they could only burn it.

Still, I'll let everyone else use OSB, I'll pay the extra for CDX.

KinAlberta
Member
# Posted: 12 Feb 2017 09:22pm
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Poly is cheap and can be tuc taped together. Seems like a cheap way to shed most of any rain that falls. If it's just for a week or so, wouldn't it then still be good enough to reuse say as vapour barrier, etc.

MtnDon
Member
# Posted: 12 Feb 2017 10:32pm
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Quoting: KinAlberta
Poly is cheap and can be tuc taped together. Seems like a cheap way to shed most of any rain that falls. If it's just for a week or so, wouldn't it then still be good enough to reuse say as vapour barrier, etc.


Tied that and ended up with water trapped under the poly. Tint pin prick like holes appeared all over as the poly was walked on, worked on, while trying to get walls / roof dried in. I do not recommend that.

Rdkng07
Member
# Posted: 12 Feb 2017 11:06pm
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I used GP DryPly if I remember correctly. It was 23/32 tongue and groove with a orange wax type coating. It was in the elements for several weeks and faded a little, but structurally was in perfect shape.

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