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Discussion Starter · #1 ·
Hello, there has been seemingly endless discussions on this issue but after looking around I was unable to find a thread dedicated to maximizing evidence and minimizing words. I have just worked on two different houses on Cape Cod and they are two miles apart, have the same type of Cedar shingles and the only noticeable difference is one has Tyvek and the other Tar Paper.

The Tyvek was installed 7 years ago and it has already begun to disintegrate and the nails are rusting out.

The tar paper was installed 22 years ago and has good integrity with minimal rust on the fasteners.

I do have pics of both that I will post but unfortunately am still learning how to resize pics to get them in line with the maximum attachment sizes.

So if anyone has pics of Tyvek or tar paper behind cedar siding (any kind of Cedar) please post them so we can let them speak for themselves. Just state climate/location, type of siding, and date of installation. As soon I get my pics resized will post them up.

Thanks!
 

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I have seen more rot in new houses with house wrap than old houses with none.

Take that to mean whatever you want.
 

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Yes but it seems so consistent...
 

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If be more interested in the age range of the homes, type of insulation used, type of vapor barrier used with that insulation, type of windows used, etc.

Now don't get me wrong. I'm not defending Tyvek, only saying there is more to the story than just Tyvek vs felt. At this point I'm 100% converted to Zip System.
 

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Last tear off and reside I did was a house built in '86. Tyvek under cedar clapboard. Tyvek looked like Tom's picture, and the cedar was in sorry shape. Aside from the point where one of those ugly, overpriced, greenhouse rooms was attached to the house, there was very little rot.

Andersen glider in that pic, Tom?
 

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Probably something abnormal going on there.
 

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Discussion Starter · #15 ·
Here are the pics and info:

Location: Cape Cod--Houses are 2 miles apart and both less than a mile from the Atlantic.

Age: Tyvek-7 years

Tar paper-22 years

Type of siding: Red Cedar


The darker red areas around the nail holes is not simply rust but rather tannin bleed because the fasteners literally create bleed holes for the saturated tannin to escape. As this acid damages the Tyvek there is absolutely nothing stopping the moisture build up on the sheathing.


Even homes built with the best systems cannot stop the tannic acid from invading the Tyvek and the only way to stop it is to place some type of heavy duty barrier between the shakes and Tyvek. Vapor barriers, climate, humidity are irrelevant to the problem of tannin bleed because none can stop the bleeding and at best slightly slow it down.

Back priming red cedar to prevent tannin bleed is like using a Bible to remove lying from politics. The great benefit of cedar shingles is they contract and expand and if one were to apply a primer heavy duty enough to stop the tannin bleed the only result is the new problem of the exterior side of the shake breaking off from the inside due to loss of flexibility thus allowing more moisture to build up.

Tyvek exacerbates the problem because it encourages vapor to escape from the inside and as we all know inside and outside air are always at different temperatures and moisture content. In a nutshell, Tyvek never allows the space between the shingles and sheathing to dry out.

Im hoping the pics help explain because they provide the best evidence. The originals do a better job visually but had to crop these down to meet board requirements.
 

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Discussion Starter · #16 ·
Regarding the pics Tom posted, it looks like there is another layer of material between the black paper and sheathing. Anyone else see it?
 

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Discussion Starter · #18 ·
I have seen it too,most likely a tannin reaction,OP do you know if the cedar is back primed?

there are a few post on here where a Dupont rep has posted,maybe they would like to hear from you..:whistling
DuPont recommends back priming but that is a farce created from the first wave of evidence proving Tyvek to be the wrong wrap under cedar.

We have all seen knots bleeding through primed and painted trim and the tannin content in red cedar is ridiculously higher than those pine knots.

I have briefly discussed this with an attorney who represents DuPont and his...hesitation helped motivate looking into this even further.

The biggest concern is mold because people (especially kids and pets) are at a huge risk of getting sick from it without ever knowing it is in their house.
 

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Discussion Starter · #20 ·
The solution for the problem is using a rain screen so the moisture isn't trapped between the WRB and the back of the siding.
This was a solution I had looked into and it did not seem cost effective and the tannin can run which is why even fur stripping is a temporary band aid.

Seems tyvek can be used behind several materials but with red cedar it causes nothing but problems.

With tar paper being a vapor retarder it allows the cedar to dry out periodically which is why on the pic I posted of the 22 year old siding the paper was still fully in tact.
 
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