Use of ThermoPly without underlying structural sheathing?

1st: Is there any acceptable reason why a builder would put ThermoPly Green Non-Structural vapor barrier up on exterior walls without putting Plywood, OSB, or other structural sheathing underneath?

Reason for question: While inspecting a friends house, new construction (wood frame, monolithic slab on grade, brick veneer) framing stage with roofing starting to go up I noticed the use of Plywood sheathing with ThermoPly Green on about 50% of the wall space and only the ThermoPly Green with no plywood on the rest. I could determine no rhyme or reason to where Plywood sheathing was installed and where only ThermoPly was installed. Unless this is a temporary measure to keep water out until a later stage in framing I can’t see how this could be acceptable. If it is temporary, I’ll have to watch closely to make sure they pull it off and put proper structural sheathing underneath and put new ThermoPly up over the sheathing. I tried to upload a few pictures but the msgboard does not like my 7.2 megapixel pictures and my photo editing software seems to reduce the pictures to fuzzy useless blobs when I try to shrink the pictures down to somthing the site will accept.


Send me the pics, I’ll post them for you.

Or try

Your pics must be sized under 640 pixels

You can bet they will not take those out and add OSB later…

All corners should have structural panels or let-in bracing of some type.
I see some houses around here that get past the county inspectors too.

Thanks for the replys. Bruce, your post and a book I picked up to strengthen my knowledge in this area gave me the answer I needed. I was surprised as on all the houses I’ve monitored (or the four I’ve had built over the years) the builders always sheathed the entire exterior wall with Plywood or OSB before putting up ThermoPly or some other moisture barrier. I hadn’t realized that the requirements only called for Plywood or OSB at the end of walls and in the middle of walls over 25’. This builder is obviously meeting the minimum requirements only. It won’t be as structurally strong against lateral forces but it is not techncally wrong.

David - I’ll email you one or two pics as soon as my laptop is repaired (hard drive crashed).

Thanks again,


I am having a new home built in western Pennsylvania. The builder is using what I believe is Thermoply. It looks like a big sheet of styrofoam about an inch thick. He is NOT using OSB. Should I have him put OSB on it AND the styrofoam, or just OSB??? I’ve never had a home built before, and don’t know what is best. Thanks.

From my understanding thermo ply can be red (structural) or green (non structural) Structural at the ends and 25 foot intervals should be ok and homes are built that way in many places.

Advise you find a qualified Phase Inspector familiar with building standards in your area. Hire him/her to report and document the work so you and the builder can address the shortcomings as they arise. The monies spent for this may save large $$$ on down the road.

Good Luck

When using the plywood/osb corner sheathing with foam sheathing (thermoply) fill method it is standard that either rows of solid blocking or diagonal steel angles be used to keep the wall from shifting. If that method is used typically most building inspectors I have come across require plywood not osb at the corners. That method works but if you can afford to have the entire house sheathed in plywood/osb it is a much more sound finished project. Unfortunately with all the ways to skirt building codes to save a dollar, now people usually don’t find out the quality of they’re builder until to late. You wouldn’t believe some of the things that I saw in my experience performing site inspections for the architectural firm I worked for the builders would drive me crazy. A good builder will either quote you the higher price and plan to do it that way from the beginning or they will at least try to sell you on it that way you can not blame them later. It’s a shame with all the new technologies the builders seem to build cheaper more poorly built homes than ever, but why complain job security for the future I guess.

Bradley Schumacher

Bradley J Inspections
Minooka, IL

P.S. Sorry I run on a bit in my posts

Haven’t seen this product in use much around here yet.

Can some elaborate on the reason for it’s use. Is it a cost factor, energy plus, or labor savings of any kind.

With an r-value of 15, I can’t see anything wrong with it’s use under vinyl siding.

Marcel :slight_smile:

The R15 quoted is not for the Thermoply itself but in a wall system with drywall, fiberglass batts (probably R11-12), and siding.

There are a lot of statements that amount to “smoke and mirrors” (my favourite term when dealing with foil R value claims), are misleading or don’t fairly compare their product to others!! I don’t have the time now to dissect the ad claim by claim, but overall, it would not be a product I would have in a house of mine.

Imagine recycled toilet paper with some weather treatment applied. Very easily torn (minimal physical effort) kinda like toilet paper, oh, I said that already.

Some of the cookie-cutter builders also have their logo printed on the product as if that is a sales feature they tout.

Just blares out to me when I pull into one of these neighborhoods they are building to the worst they can legally (code) get away with.

Thanks Barry for the insight and you to Brian B., but how in hell do they get this sh$t to perform to the required Code shear wall and lateral stabilities Engineered in today’s World?

Someone getting paid under the table here or what?

Thanks for the info. Interesting.
Let you know when it starts coming up here and will notice when they don’t speak english. ha. ha.
Hell, I should not say that, I can’t speak English. :wink:

Marcel :slight_smile:

marcel, some of the structural ply has wood strips and when nailed on 3" oc suppose to be adequate. I wouldnt want it on my house. Over 50 percent of the homes in my area have this material on them.