plywood over the housewrap

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#1

Originally Posted By: jmyers
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I would like some opinions on the following scenerio:


The home I just inspected reportedly had two sets of plywood under the siding. The first set of plywood is covering the studs on the house with a house wrap covering the plywood. The next set of plywood is covering the house wrap over the vapor barrier of the house wrap which was then covered with vinyl siding.

Does anyone see any problem with this. If so, please explain why. Please give only facts, no opinions.

Thanks,

Joe Myers

#2

Originally Posted By: gbeaumont
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Hi to all,


Jim, the original house wrap would to some extent still allow the structure to "breath" but if there are any areas on the siding that are not fully protecting the second sheathing (which is not uncommon) then I would be concerned about moisture being able to migrate into the second sheathing as there is no moisture barrier at that level.

though call for a report.

Regards

Gerry

--
Gerry Beaumont
NACHI Education Committee
e-mail : education@nachi.org
NACHI phone 484-429-5466

Inspection Depot Education
gbeaumont@inspectiondepot.com

"Education is a journey, not a destination"

#3

Originally Posted By: Guest
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Joe,


The primary purpose of a housewrap or felt over continuous sheathing is the creation of a drainage plane. Secondarily, the barrier must be breathable to allow any moisture that gets behind it to get out. The outer layer of ply has no drainage plane to protect it and will succumb to inevitable water intrusion.
Plywood is a very effective vapor and wind barrier on its own and theoretically if seams were sealed effectively, no further barrier would be necessary; two layers of plywood sandwiching a housewrap in a mixed climate could easily create a scenario of a moist wall cavity if the interior of the home isn't extremely well detailed. The issue would be most prevalent in winter in PA.

If you google Joe Lstiburek, or research at the JLC online forums there's reams of research that can be had for free, and that you can apply to the home you're inspecting.

There are no hard facts about whether it'll work, there's too many variables.

#4

Originally Posted By: jmyers
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Gerry,


Jim who? You better lay off the merlot for a while dude! ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)

Anyway, thanks for the response. I did not really see this as a problem, although I am not totally without concern for this condition. Like Chad stated, it is creating a plane which could effectively trap the moisture between the house wrap and the siding which would effectively damage the secondary set of plywood over time, given the right set of conditions.

Like I said, I am not without concern but I don't believe it is a big deal.

Thank you both for your replies.

Joe Myers

#5

Originally Posted By: roconnor
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The IRC would require a vapor barrier between the siding and the sheathing. There is a reason for that as Chad pointed out, and it could lead to significant and costly deterioration.


If it's an existing home were there any signs of sheathing deterioration? If it's a new home there's just no excuse.

Just my 2 nickles

--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

#6

Originally Posted By: jmyers
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Bob,


The story goes, the neighbor that I spoke too, informed me that originally the siding was to be installed by Sears. When the owner found out that no vapor barrier was included in the price of the installation, he requested it be installed. Sears of course would not do so without additional costs to the owner. The owner then fired them and it was left without any siding for a few years.

After a few years and of course the big orange the owner decided to do it himself. The neighbor informed me that the owner installed plywood over the house wrap, then installed the siding himself.

The house is pretty young, around 25 years. I could not see this situation, so I did not comment on it to the buyer.

I personally have had aluminum siding on a house that I owned, without any house wrap or vapor barrier and when the siding was removed, there were no problems with water penetration, so logically I did not see it as a problem.

Thanks for your opinion.

Joe Myers

#7

Originally Posted By: jstevens
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hey guys there should be a vapor barrier under the sidin.the plywood will rot under the windows and around the doors etc .water gets in behind the sidin .also around the j channel.vinly sidin can not be made water tight .so i would report it as a defect my 2 cents