# Plywood sheathing question



## davinci

how long can plywood sheathing be exposed to outdoor elements? just curious,i see a few new construction buildings that were constructed and the tyvek was'nt put up yet,..about how long can plywood or OSB be exposed?


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## mics_54

depends...exposed to elements is rather ambiguous. Do you mean soaked constantly? The elements are different geographically. Given the criteria I would say...a week to 20 years.


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## loneframer

One of the reasons I like to sheath the walls after they are standing is to limit their exposure to a minimum. Many of the buildings I've framed are on pilings and skirt walls are framed from the bottom of the first floor deck to below grade in order enclose the lower level. In some cases, such as the pics, I have packed the top plate with a rip of 1x material so the rafters can be pulled tight at the birdsmouth and still get plywood behind the rafter notch. After the building was completely sticked, the sheathing was installed.

To answer the OPs question, I have seen buildings with CDX fir sit for weeks with no huge downside to exposure. OSB tends to grow in thickness when exposed to drenching downpours, so should be covered promptly after application. I always space the ends and sides of the sheets to eliminate the possibility of the sheets growing and binding or buckling. I have seen it happen with both types when hung without spacing.


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## Kent Whitten

Also would depend on the type of ply. Like SYP ply wouldn't last too long before it was buckling all over the place. Advantech sheathing holds up quite well. I have had a piece sitting under snow all winter and that came from last year, all winter and then in mud and dirt. It's holding up just fine. Little discolored.


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## Trim40

I have some osb side panels for my trailer. They have been outside for 3 yrs. The edges have swollen, but they haven't peeled apart.


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## Inner10

From my rather limited experience:

Cheap OSB from Bargan Building Materials (the name should have really tipped me off) started to flake off like mad after less then a year of exposure.

Decent OSB installed beside the cheap stuff has actually started to weather and turn grey, holding up very well (after 12 years)....I should really get off my arse and finish my own projects.

Plywood.....a long time...

I think if you get the sheets up and off the ground they will last a long time since the water never sits on them for an extended period of time. If the sheets are sitting against the dirt horizontally then you may have something to be worried about.

From what I've seen wood gets damaged when it gets wet and stays wet. Not when it gets wet and dries out. 

Take my opinion with a grain of salt for I have very limited experience in that field.


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## woodworkbykirk

my theory is dont leave it exposed long enough to find out!!

one of my neighbors did a 2 storey addition on their house themself, and they worked on it in the evenings and weekends. i basically watched the osb turn from new to grey over a period of 9 or 10 months before he finally started getting it covered with tyvek. from there another 2 or 3 months before he went full tilt on siding


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## wheeler

untreated plywood maybe a few rains on the 5/8. you can get away with more using 3/4 t&g, roof or subfloors. pt goes a long time, don't know the end points. we apply our own water proofing, thompson's or california, for untreated sheathing that has lengthy exposure periods during construction but there are some expensive poducts you can buy if you're concerned with a phase of the project involving lengthy exposure.


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## davinci

so a roof or sheathing(plywood/OSB) can go exposed for about 3 or 4 weeks ?


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## mics_54

I would say probably but that means the roof will leak like hell and soak everything below it. With everything there is a cost /benifit ratio.


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## RebelNY

Looks like a great framing job


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## RebelNY

It can go a few weeks but it is always best to cover the roof sheathing with paper or membrain right away and if you are sheating your walls while it is lying down then you might as well tyvek it too and not worry about how long you have .


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## oldfrt

Have a friend that put a rather large addition on his home about 20 years ago.
Some call it a labor of Love as he has yet to finish the interior,
and has done most himself.
We put siding on about 10 years ago.
Pieces of tyvek had been littering his neighbors yards for about 5 years.
The plywood,believe it or not,was still in good shape after about 5 years of complete exposure.


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## wheeler

davinci said:


> so a roof or sheathing(plywood/OSB) can go exposed for about 3 or 4 weeks ?


plywood.


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## curtis fulton

considering that most lumberyards have materail stored in the elemants i would say months and maybe years ,


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## KennMacMoragh

On roofs, I've seen plywood de-laminate from sitting for too long. Not that big of a deal though, you can bang on it and shoot it down with your roofing gun. OSB, I've never seen a problem on roofs, but I gap my sheets, and I haven't had any houses sit around too long before the roofing goes on. If you had OSB on a roof with the sheets slammed tight together, and then it sat in the rain for two weeks, I could see there being a problem.


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## KennMacMoragh

curtis fulton said:


> considering that most lumberyards have materail stored in the elemants i would say months and maybe years ,


Yeah but lumberyards have roofs, that's different than being directly rained on.


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## PA woodbutcher

KennMacMoragh said:


> On roofs, I've seen plywood de-laminate from sitting for too long. Not that big of a deal though, you can bang on it and shoot it down with your roofing gun. OSB, I've never seen a problem on roofs, but I gap my sheets, and I haven't had any houses sit around too long before the roofing goes on. If you had OSB on a roof with the sheets slammed tight together, and then it sat in the rain for two weeks, I could see there being a problem.


Your nailing down plywood that has already started to de-laminate?


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## KennMacMoragh

PA woodbutcher said:


> Your nailing down plywood that has already started to de-laminate?


Yes, to get rid of the bubble.


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## curtis fulton

ok but also being de laminated also means that it also is a little weak , form soaking up the water meaning osb , plywood i wouldnt be to concerned about


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