Vapor Barrier Exterior Wall

**Tom Hennessy** · 08-26-2016, 04:41 PM

We've inadvertantly wrapped our addition with waterproof roof wrap, instead of Tyvek, in effect now having two vapor barriers, exterior and interior.
How can we remedy this?
Can we tile knife open the cracks in the wrap, at those points in the osb sheeting, which were left open to allow the wall to breathe?
Just remove the waterproofing from over those cracks?
The manufacturer says it is virtually impossible to remove but haven't really tried yet.

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**Jim Luttrall** · 08-26-2016, 07:52 PM

Originally Posted by Tom Hennessy

We've inadvertantly wrapped our addition with waterproof roof wrap, instead of Tyvek, in effect now having two vapor barriers, exterior and interior.
How can we remedy this?
Can we tile knife open the cracks in the wrap, at those points in the osb sheeting, which were left open to allow the wall to breathe?
Just remove the waterproofing from over those cracks?
The manufacturer says it is virtually impossible to remove but haven't really tried yet.

Check with the product manufacturer for the perm rating (permeability) Even "water proof" products tend to have some degree of permeability and compare to see with other products to see where you really stand. Sometimes you get a serendipitous surprise.

http://buildingscience.com/documents...vapor-barriers

**Tom Hennessy** · 08-27-2016, 05:04 AM

Originally Posted by Jim Luttrall

Check with the product manufacturer for the perm rating (permeability) Even "water proof" products tend to have some degree of permeability and compare to see with other products to see where you really stand. Sometimes you get a serendipitous surprise.

http://buildingscience.com/documents...vapor-barriers

It is Soprema 1100T

http://soprema.us/products/wall-syst...ck-1100t/25338

Would these be the specs I'm looking for?

https://www.airbarrier.org/materials/index_e.php

Soprema Inc. www.soprema.us	SopraSEAL Stick 1100T	Section 072761
Air Permeance (ASTM E2178): < 0.0005 L/(s • m²) @ 75 Pa [0.0001 cfm /ft² @ 1.57 psf] Water Vapor Permeance (ASTM E96 - desiccant method): 0.89 ng / Pa•s•m² [0.016 US Perms] Water Vapor Permeance (ASTM E96 - water method): 1.8 ng / Pa•s•m² [0.031 US Perms]

**John Kogel** · 08-27-2016, 07:51 PM

Nanograms are teeny tiny grams. That stuff is literally waterproof.

I'll bet it will peel off if you get it warm with a heat gun. Modified bitumen (petroleum product, so flammable).

**Tom Hennessy** · 08-28-2016, 04:45 AM

Originally Posted by John Kogel

Nanograms are teeny tiny grams. That stuff is literally waterproof.

I'll bet it will peel off if you get it warm with a heat gun. Modified bitumen (petroleum product, so flammable).

Thanks,
Sooo, in your opinion, would all of it have to be taken off or could we peel off that which is covering the cracks between the osb which we had left open to the wall could 'breathe' ..?
Does the board itself actually breathe/allow for drying condensation or is it only the cracks between the osb which we left, so it could breathe?
Would a person only need an access to 'breaths', a method of calculating how much area has to be open and then covered with breathable material such as felt or 'tar paper' .. ?

**Jim Luttrall** · 08-28-2016, 02:08 PM

Originally Posted by Tom Hennessy

Thanks,
Sooo, in your opinion, would all of it have to be taken off or could we peel off that which is covering the cracks between the osb which we had left open to the wall could 'breathe' ..?
Does the board itself actually breathe/allow for drying condensation or is it only the cracks between the osb which we left, so it could breathe?
Would a person only need an access to 'breaths', a method of calculating how much area has to be open and then covered with breathable material such as felt or 'tar paper' .. ?

Much depends on your climate. Here, we likely would not get in to much trouble if we just had a few holes but even in the same state, Houston has MUCH more humidity and you might get into trouble.
Much also depends on the quality of the primary vapor barrier and its permeability rating.
I suspect you are in a very cold climate with lots of moisture so I would be telling my client to remove the second vapor barrier... but I'm not there to see it.

**John Kogel** · 08-28-2016, 04:14 PM

Jim is right. In Alberta you have heat on for 4 or 5 months of the year, warm interior, cold exterior. If any warm air which carries moisture finds its way into the wall, moisture will be absorbed by the OSB.
It may not happen right away, but the OSB will rot. At the very least, slash the membrane top to bottom about a foot apart. If a knife wont cut it, use a tile cutting blade on a skilsaw set to a shallow depth, or something similar.

**Tom Hennessy** · 08-29-2016, 05:22 PM

Originally Posted by John Kogel

Jim is right. In Alberta you have heat on for 4 or 5 months of the year, warm interior, cold exterior. If any warm air which carries moisture finds its way into the wall, moisture will be absorbed by the OSB.
It may not happen right away, but the OSB will rot. At the very least, slash the membrane top to bottom about a foot apart. If a knife wont cut it, use a tile cutting blade on a skilsaw set to a shallow depth, or something similar.

Thanks.
It stumped my carpenter who said he watched them put it on but thought it was some 'new type' of practice.
I guess, since there is such a difference of opinion, 'tear it off' to 'slash', would make one kind of wary how to remedy to meet my city inspectors opinion, being highly variable, some say?

**Tom Hennessy** · 08-31-2016, 05:34 AM

Originally Posted by John Kogel

At the very least, slash the membrane top to bottom about a foot apart. If a knife wont cut it, use a tile cutting blade on a skilsaw set to a shallow depth, or something similar.

I may have misunderstood you here. Do you mean slash it in order to take it off? or do you mean slash it to allow it to breathe?

**Gunnar Alquist** · 08-31-2016, 08:26 AM

I'm not clear about this installation. Is this wrap over the OSB? If so, then you should be able to take it off. It will be a pain though.

I would be concerned about leaving it in place, even if it was sliced and would want it removed. The slices may not provide enough area for the vapor to escape through. The contractor who put it on should make it right.

**Tom Hennessy** · 09-01-2016, 07:36 AM

Originally Posted by Gunnar Alquist

I'm not clear about this installation. Is this wrap over the OSB? If so, then you should be able to take it off. It will be a pain though.

I would be concerned about leaving it in place, even if it was sliced and would want it removed. The slices may not provide enough area for the vapor to escape through. The contractor who put it on should make it right.

Thanks everyone, cut six inch slashes, foot were too hard to pull, and stripped it off with a little grunting but didn't need to scrape.
Thanks again.