# Interesting question on tyvek and felt paper for roof



## enforcer (Aug 25, 2008)

A homeowner asked why tyvek is used on a wall but not on a roof..
If tyvek is supposedly superior to felt paper on walls, why not on a roof?
What are some so called technical reasons?


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## shanekw1 (Mar 20, 2008)

Try to walk on tyvek on a roof.


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## enforcer (Aug 25, 2008)

Yes, it's too slippery for a roof when walking..
I meant besides that are there any other reasons?


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## SAW.co (Jan 2, 2011)

When you put a nail thru felt the asphalt sticks to the nail & seals around it.
Tyvek wont do that.


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## ohiohomedoctor (Dec 26, 2010)

I would think it would be a massive waste of money since roofing material is typically more waterproof than siding installations. Never seen a roof with weep wholes. Except the ones the europeans post with gutters that run inside the home. That still amazes me.


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## Tinstaafl (Jan 6, 2008)

From DuPont's website:



> *9. Can DuPont™ Tyvek® be used in attics? On roofs? Under Floors? On the interior?*
> 
> In 2006 DuPont introduced Tyvek® AtticWrap™, a unique, breathable membrane that helps create an airtight seal to reduce air leakage and energy loss through the roof. All other DuPont™ Tyvek® products in Canada and the US have been tested and approved as a product to be installed behind exterior walls.


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## ohiohomedoctor (Dec 26, 2010)

So it is settled. It can be done with the right budget, on low slope ranches, when its not raining. I always thought about rolling aqua defense on an entire roof structure. What an up sell :whistling:


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## TNTRenovate (Aug 19, 2010)

I guess the real question, that no one seems to have a consensus on is, what is the purpose of tar paper/felt?


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## fourcornerhome (Feb 19, 2008)

We stripped a roof off that had no felt, and the shingles were stuck to the plywood. The worst tearoff ever !


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## RandyB1986 (Jan 2, 2009)

Tyvek Atticwrap I have installed didn't go on top of decking.....it was installed in attic under decking. Tyvek keeps water out but lets air escape.....on a different but same note, why do some old timers use black paper on walls instead of Tyvek?


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## Tom Struble (Mar 2, 2007)

:whistlinghere we go :laughing:


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## Tom Struble (Mar 2, 2007)

Tinstaafl said:


> From DuPont's website:


this goes in the attic


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## enforcer (Aug 25, 2008)

The question would now be, if tyvek is a water barrier on walls, why won't it be a water barrier on a roof? Even though shingles stick to tar paper and seal, isn't tyvek just as good as sealing when using staples?


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## RandyB1986 (Jan 2, 2009)

enforcer said:


> The question would now be, if tyvek is a water barrier on walls, why won't it be a water barrier on a roof? Even though shingles stick to tar paper and seal, isn't tyvek just as good as sealing when using staples?


Well sure it would keep the water out but what is the sense...buy synthetic if you are just wanting to waste your money. Hell, you can use old grocery bags if you so desire......I have seen it done!


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## Tom Struble (Mar 2, 2007)

so they can sell you this

http://construction.tyvek.co.uk/Tyvek_Construction/en_GB/products/roofing/index.html

it's never been tested for that use which besides being unsafe is the reason you dont see it as a suggested use


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## Tom Struble (Mar 2, 2007)

TNTSERVICES said:


> I guess the real question, that no one seems to have a consensus on is, what is the purpose of tar paper/felt?


to give me an Riz something to talk about:thumbup:


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## loneframer (Feb 13, 2009)

RandyB1986 said:


> on a different but same note, why do some old timers use black paper on walls instead of Tyvek?


Because some of us "old timers" started using felt, made the switch to Tyvek and after several years, were not impressed.

Felt has some properties that plastics don't and that's why I prefer it.

http://bct.eco.umass.edu/publicatio...-felt-paper-and-weather-penetration-barriers/

from the link


*Housewrap or Felt?
*Based on our testing, if I were buying a housewrap today, I would choose either Tyvek or R-Wrap, because they display the best water resistance. But so far, I’ve avoided the million dollar question – housewrap or felt? The truth is, there’s not million dollar answer. In general, I don’t think it matters a whole lot. If you get the flashing details right, and are careful installing the building paper, you will prevent 99% of the moisture problems caused by wind-driven rain and snow. Either product, housewrap or felt, will provide an adequate secondary drainage plane. And either product is permeable enough to allow interior moisture to escape.
As it happens, I have felt paper on my own home, and if I could choose between felt and housewrap and do it over again, I’d still choose felt. That’s because I believe that under certain circumstances, felt outperforms housewrap. For example, an ice dam or roof leak may allow liquid water to get behind the felt or housewrap. It’s also possible for the sun’s heat to drive water vapor through the housewrap from the outside, where it can condense on the sheathing. In either of these cases, you now have liquid water on the wrong side of the wrap. Under these conditions, the liquid water would be trapped by the housewrap, which is permeable only to water vapor. Felt, on the other hand, will absorb the water, and more quickly dry to the outside.


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## Tom Struble (Mar 2, 2007)

be honest with you Riz the main reason i use it is it's superior rip resistance,less fasteners needed less penetrations into the envelope,tears and damage easier to fix,integrates with SA tape flashings

and lighter weight,easier it is to use the better it can be installed imo

other reasons are it won't absorb like felt,i know this is exactly opposite of your view

otherwise i think they are both suitable for wall wrb


that umass thigs been around for years by the waynot impressed


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## welterweight (Nov 10, 2009)

For walls, tyvek has a much higher perm rating than felt.
If felt gets wet,it's perm rating rises dramatically but there is a catch most don't know about. Felt has tiny little holes and as it gets wet, these holes expand make it more permeable..sounds good right. Not really. When those holes expand, water is able to get through. I will stick to tyvek on walls and 30 lb felt on the roof.


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## loneframer (Feb 13, 2009)

Tom Struble said:


> be honest with you Riz the main reason i use it is it's superior rip resistance,less fasteners needed less penetrations into the envelope,tears and damage easier to fix,integrates with SA tape flashings
> 
> and lighter weight,easier it is to use the better it can be installed imo
> 
> ...


It's been around for years, but the reality hasn't changed. We can beat this thing to death. The only reason I even bother is to make people aware of their options so they can make an INFORMED decision on what product to use.

I base my decision on my own personal experiences and observations, as I know you do. We have opposing views, but both of us sleep well at night knowing we've made the right decision.:thumbsup:


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## katoman (Apr 26, 2009)

Last big roof job we did the roofer (with my permission) installed a tyvek type product. It is called roof guard. 

The only real advantage I can see over tar paper is that is seals the roof if you can't get the shingles on right away. Tar paper breaks down when wet.

We did a small roof 2 weeks ago and we I&WS two rows, then tar paper. I'll use either method, depends on the job.


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## TNTRenovate (Aug 19, 2010)

seeyou said:


> 1) It is there for protection prior to installing the roofing material.
> 2) It is a second barrier
> 3) It provides a barrier between the shingles and the underlayment. The underlayment would end up drawing out the petroleum in the shingles and drying them out.
> 4) I have heard that not only is it there to protect against weather before the shingles are installed, but makes it easy to remove during tear-out.
> ...



I guess I am looking at more than just another opinion. Don't get me wrong, I am not doubting that you could be right, but it's just another contractor telling me what I have already heard. Is there any actual manufactures or industry data that explains the purpose of tar paper.

As far as gravity helping on a horizontal plane, it's also working against it, unlike a vertical plane. But slope does come into play.


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## seeyou (Dec 12, 2008)

"Is there any actual manufactures or industry data that explains the purpose of tar paper."

All shingle manufacturers have some sort of requirement in their installation instructions. Most suggest/demand their proprietary products. But, in a round about way, all your questions are answered. 

Most metal products have similar installation requirements.

But common sense/experience certainly answers the questions. You want to use tyvek on the roof or skip underlayments entirely, be my guest. You might even get away with it. 

http://en.wikipedia.org/wiki/Tar_paper


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## TNTRenovate (Aug 19, 2010)

seeyou said:


> "Is there any actual manufactures or industry data that explains the purpose of tar paper."
> 
> All shingle manufacturers have some sort of requirement in their installation instructions. Most suggest/demand their proprietary products. But, in a round about way, all your questions are answered.
> 
> ...


Like I said, no one, even those that do it, can give me an answer. I think it's one of those things that you are supposed to do and don't really know exactly why.

BTW Wikipedia is a terrible source of information. Even I can edit an entry, and that's scary.


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## seeyou (Dec 12, 2008)

TNTSERVICES said:


> Like I said, no one, even those that do it, can give me an answer. I think it's one of those things that you are supposed to do and don't really know exactly why.
> 
> BTW Wikipedia is a terrible source of information. Even I can edit an entry, and that's scary.


You've been told exactly why. You've been given the answers repeatedly. You just don't like the source and apparently not the answer either. Doesn't mean it's wrong. And just because you can edit Wikipedia doesn't mean you do. 

Did you go along with the "fire will burn you" story or did you have to learn that for yourself. 

Here's what I know and you can't prove me wrong:

If it rains and there's nothing covering the roof, it will leak.

Asphalt shingles can (but don't always) stick to the sheathing. Wood and asphalt have different expansion rates.

If a couple of shingles blow off, the odds are better that no water will get inside the attic if there is underlayment of some sort. 

Tyvek is designed for wall applications. 

Fire is hot.


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## TNTRenovate (Aug 19, 2010)

seeyou said:


> You've been told exactly why. But not the source, other than the guy who trained meYou've been given the answers repeatedly. Answers, but even roofers disagree.You just don't like the source and apparently not the answer either. Why do you feel I don't like the answers. Just a question about a comment. Doesn't mean it's wrong. And just because you can edit Wikipedia doesn't mean you do. But it does mean that there is no one really proofing it either. That's the difference. Wikipeia should not be anyways definitive source.
> 
> Did you go along with the "fire will burn you" story or did you have to learn that for yourself.
> 
> ...


You need to read my posts. I have said that the answer I have been given may be the right answers, but no two roofers agree.

_"I am not doubting that you could be right, but it's just another contractor telling me what I have already heard."_

The question I am asking is, what is your source? Other roofers? Is there something that says it in writing? If you don't know, don't get mad at me. Just don't try to answer my question with, trust me.


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## seeyou (Dec 12, 2008)

TNTSERVICES said:


> You need to read my posts. I have said that the answer I have been given may be the right answers, but no two roofers agree.
> 
> _"I am not doubting that you could be right, but it's just another contractor telling me what I have already heard."_
> 
> The question I am asking is, what is your source? Other roofers? Is there something that says it in writing? If you don't know, don't get mad at me. Just don't try to answer my question with, trust me.


Which two roofers don't agree?

Wikipedia said it in writing. You didn't like that source. 

I've written it 3-4 times in this thread. You didn't like that either. 

How's this:

http://www.gaf.com/Roofing/Resident...ection/Shingle-Mate-Roof-Deck-Protection.aspx

or this:

http://www.gaf.com/Roofing/Resident...Protection/Roof-Pro-Roof-Deck-Protection.aspx

or this:

http://www.gaf.com/Roofing/Resident...otection/Deck-Armor-Roof-Deck-Protection.aspx

or this: 

http://www.certainteed.com/resources/IRSHomeownerBrochure.pdf

or this:

http://roofing.owenscorning.com/professional/accessories/underlayment/fiberglas-felt.aspx


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## BrandConst (May 9, 2011)

I imagine tyvek can be used on a roof but who would want to be exposed to falling off of a roof that slick? Funny thing is and it's a little off topic, there are two houses side by side in Galveston that are completely shingled with a 50yr shingle. The whole house, front, back and sides, not to mention the roof. I'm not too sure of the benifit but it's certainly a conversation topic everytime I go to the island.


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## TNTRenovate (Aug 19, 2010)

seeyou said:


> Which two roofers don't agree?
> 
> Wikipedia said it in writing. You didn't like that source.
> 
> ...


Which two roofers don't agree. I have had two roofers work for me, both giving a different reason it is used. One said it was for protecting before shingles went down and then easy tear off, and the other was for a second barrier and that it had nothing to do with easy of removal.

Again, Wikipedia is self policed source of information. I just added:

"However, there are various reason given why tar paper is used, the original reason remains unknown." to the tar paper entry. While it may be removed or edited by someone it is up right now for millions to see.

Thank you for posting reliable sources. :thumbsup:


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## ohiohomedoctor (Dec 26, 2010)

I always thought it was there to give the builders an extra week to finish there houses. :whistling:


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## Tom Struble (Mar 2, 2007)

tyvek gives you 6 months:clap:


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## ohiohomedoctor (Dec 26, 2010)

I know the home they built across the street from me was under paper for nearly 5 months. A buddy of mine did the drywall and said everything was bone dry.


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## Tom Struble (Mar 2, 2007)

yea.. thats what i tell everybody too:whistling


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## ohiohomedoctor (Dec 26, 2010)

Tom Struble said:


> yea.. thats what i tell everybody too:whistling


Riiiiight.... :whistling:


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## SeanInOnt (Jan 7, 2011)

MJW said:


> There are plenty out there that had a sideline framer slap up some siding on their house that have no idea how water works except that when it comes out of the sky, they get in the truck and head home.
> 
> I've seen rotten wood and rotten walls that had nothing to do with flashing or wall wrap. There are thousands of houses around here that were built 10-20 years ago with plenty of moisture in the walls. Our code calls for us to seal our walls inside and out. Once moisture gets in and condenses, it starts mold and rusts the nails.
> I just wonder is going to start paying for this to be repaired. Homeowners ins.??? Builder's ins.????? Out of pocket? Government??


There are plenty out there that had a sideline framer slap up some siding on their house that have no idea how water works except that when it comes out of the sky, they get in the truck and head home....that was effing funny!


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## mbobbish734 (Apr 28, 2011)

Just think of the tar paper on a roof as Ditra under tile.


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## BrandConst (May 9, 2011)

katoman said:


> Last big roof job we did the roofer (with my permission) installed a tyvek type product. It is called roof guard.
> 
> The only real advantage I can see over tar paper is that is seals the roof if you can't get the shingles on right away. Tar paper breaks down when wet.
> 
> We did a small roof 2 weeks ago and we I&WS two rows, then tar paper. I'll use either method, depends on the job.


I just looked this product up, is there anything you didn't like about it? Look like a good product....what was the price of it compared to felt?


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## TNTRenovate (Aug 19, 2010)

mbobbish734 said:


> Just think of the tar paper on a roof as Ditra under tile.


Now there's an interesting idea, Ditra on the roof instead of felt.


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## ohiohomedoctor (Dec 26, 2010)

ohiohomedoctor said:


> I always thought about rolling aqua defense on an entire roof structure. What an up sell :whistling:


This would be more practical...


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## dennis (Nov 17, 2004)

You don't use tyvek on a roof for the same reason you don't lay shingles directly on Grace I&W.


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## Tom Struble (Mar 2, 2007)

who's building for 100 years?


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## Tinstaafl (Jan 6, 2008)

Tom Struble said:


> who's building for 100 years?


Apparently hardly anyone these days. Don't you find that disturbing on some level?


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## loneframer (Feb 13, 2009)

Tom Struble said:


> who's building for 100 years?


Nobody, but for true conservation of energy, shouldn't we be?


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## Tom Struble (Mar 2, 2007)

most products out there have a useful lifetime of between 15-30 years,i'm fine with that


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## loneframer (Feb 13, 2009)

Tom Struble said:


> most products out there have a useful lifetime of between 15-30 years,i'm fine with that


As a tradesman, OK. 

As a homeowner holding a 30 year mortgage, hell no.


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## Tom Struble (Mar 2, 2007)

until it comes time to pay for another 30:laughing:


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## Stephen H (Feb 18, 2011)

MJW said:


> Ya, but I've already redone roofs with felt over the I&W. What a mess that was to clean up. If the shingles are going to adhere to it, then the felt will too.
> 
> The main reason it sticks so badly is usually because the I&W was very hot when it was shingled over. This is why I still say, if it's 80+ degrees, you shouldn't be roofing. I'd recommend a new roof in January before I'd recommend installation in July or August.
> 
> I thought Grace was supposedly known for NOT sticking to the shingles. Not sure. It's too expensive to use on most residential roofs anyhow .....And way too darn sticky.


 I haven't found any of that to be the case( in my experience)

the tear-offs we have done that originally included Grace were fairly straight forward.

We don't find Grace to be too expensive for residential roofs-and we use a good amount of it. It CAN be tricky on hot weather installs but we use smaller pieces and a variety of techniques to make the hot weather install easier.

Also-last fall we found Grace High Temp which is a product we hope will be even easier to install mid summer- the jobs we used it on in the fall seemed to indicate so....

We have found that the cheaper granulated I&W products ARE a pain during Tear off and that sometimes re-decking is a quicker cheaper process( products like Certainteed wintergaurd or GAF Weatherwatch)

Best wishes,
stephen


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## Friend (Oct 30, 2010)

Tom Struble said:


> who's building for 100 years?


My house was built in the twenties. The walls are one foot of stone directly against board and baton that is about two inches thick. There is one or two layers of wall paper underneath a thin luan panel and that is it. Even worse the load of the roof is resting on a 2x4 nailed to the board and baton. The whole roof is held by the shear strength of 100 year old nails. Even with all that going against it, the house still stands because the wood is so dense and the person who built the house built it for there son with more attention and care than average.


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## Tom Struble (Mar 2, 2007)

'm not arguing that :thumbup:


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## flippinfool (Jan 6, 2009)

*Correct me if I'm wrong*

Once water passes the shingles you have other more important things to worry about. Felt paper should be SAFE to work on and properly fastened. It's only job is to protect the deck from moisture not water.


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## Tom Struble (Mar 2, 2007)

actually according to Ct it's there to maintain the U.L. rating


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## WindowsonWash (Nov 1, 2011)

Probably been said already but Tyvek is vapor permeable. This is not correct on a roof deck.


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## jmiller (May 14, 2010)

WindowsonWash said:


> Probably been said already but Tyvek is vapor permeable. This is not correct on a roof deck.


Didn't Lone just point out that felt has variable permeability? Isn't that ok on a roof deck?


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## WindowsonWash (Nov 1, 2011)

jmiller said:


> Didn't Lone just point out that felt has variable permeability? Isn't that ok on a roof deck?


Felt's permeability seems to change with moisture content helping it speed drying to one side or the other.

Felt, for the most part, is more impermeable than all of your housewraps by a large margin in some cases. Felt perm ratings are probably in the 1-4 range in most applications. Tyvek has a perm rating somewhere in the 50's which is great for walls that have an air gap behind then like brick veneer or siding, but not so much for roof decks.

The issue with something that is as permeable as Tyvek is that it will allow for moisture to get behind it via the solar vapor drive. Any underlayment that would choose should be bulk moisture impermeable and largely vapor impermeable. The roof should not be wet not require the ability to dry from between the sheathing and the shingle.

I personally would always prefer that the sheathing not be susceptible to solar moisture drive and any small amount of moisture that get behind the underlayment can dry through the plywood.


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## Tom Struble (Mar 2, 2007)

WOW you don't think that felt is just as or even more susceptible to moisture drive?yea it may start out with a higher perm rating but as vapor drive happens the more moisture the more permeable


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## loneframer (Feb 13, 2009)

Tom Struble said:


> WOW you don't think that felt is just as or even more susceptible to moisture drive?yea it may start out with a higher perm rating but as vapor drive happens the more moisture the more permeable


Sounds like Tom is starting to understand my love for felt. The more permeability needed, the more permeable it becomes.:thumbup:


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## Tom Struble (Mar 2, 2007)

:laughing:no way just the opposite:clap:


we are goin to be doin this a llllong time:thumbup:


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## loneframer (Feb 13, 2009)

Tom Struble said:


> :laughing:no way just the opposite:clap:
> 
> 
> we are goin to be doin this a llllong time:thumbup:


Wait, say it ain't so...

Felt paper is no good on a roof because of solar drive? Really?

It's been used on roofs for over 100 years and it's no good?:blink:


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## Tom Struble (Mar 2, 2007)

i never said that:no:i said felt is also subject to vapor drive


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## loneframer (Feb 13, 2009)

Tom Struble said:


> i never said that:no:i said felt is also subject to vapor drive


As is any product with a perm rating. There ain't no backflow preventers on WRB...at least to my knowledge. Correct me if I'm wrong.


Wickability (is wickability a word?) is another matter.:laughing:


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