Try to walk on tyvek on a roof.

 

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

 

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

 

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.

 

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.

 

this goes in the attic

 

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:

 

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:

 

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

 

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?

 

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...u/publications/by-title/housewraps-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.

 

:whistlinghere we go :laughing:

 

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!

 

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

 

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

 

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:

 

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.

 

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.

This is exactly what Tom and I debate. Whether or not it is a pro or a con.

The answer depends on whether or not you believe moisture can be driven through to the wrong side of the WRB. In my opinion, any product that is permeable is vulnerable to "solar drive", regardless of it's perm rating or whether it's hygro-expansive. Once water vapor is on the wrong side of the WRB, it will condense. At this point, I prefer felts variable permeability, which will speed the drying process.

 

That's it, I'm setting up some mock comparisons of my own to get to the bottom of this...I'll be out in the backyard if anybody needs me :whistling

 

How can tar paper be a second barrier, when you put a thousand nail holes in it. And don't give me that crap that it seals it self, cuz it don't.

 

The same amount of holes are driven through Tyvek during siding installation. Those nails are the bridge from siding to sheathing and I know we've all seen condensation on the back side of siding at one point or another. Water will find a way behind the WRB. How effectively you dry it out is the key. My opinion is that felt does a better job of it.

 

I covered my shed out back with 2 layers 30# felt held it down with furring strips & it lasted 3 winters before I put on the comp.

I'd like to see tyvek do that

 

Isn't that the recommended procedure for more than 6 months exposed? I read an article in a magazine not to long ago about this very subject. Covered all the houses that were being built during the end of the housing bubble.

Hmmm...I am going to have to look for that.

 

Whenever a customer does ask, I simply tell them tyvek was not meant for a roof and you certainly couldnt walk on it.
I also tell them roofing shingles seal better than vinyl siding hence less chance of water getting through shingles.
As far as permeability, felt is less breathable but a proper ventilation system such as a ridge vent and soffits mitigate any potential moisture build up.
There is no such vent system with siding.. Thats why tyvek is preferred for siding.

 

Between us all........I think Tyvek is overrated. I have torn off a bunch of siding in my days and most of it with no barrier, some with paper barrier, some with aluminum foil......I have seen houses 10 years old with Tyvek that have rotted wood. It don't really matter what you put under it, if the siding and flashing is done properly, it will last.

 

Between us all........I think Tyvek is overrated. I have torn off a bunch of siding in my days and most of it with no barrier, some with paper barrier, some with aluminum foil......I have seen houses 10 years old with Tyvek that have rotted wood. It don't really matter what you put under it, if the siding and flashing is done properly, it will last.

And Tyvek has to be properly detailed at openings just like any underlayment. I've always understood that the main reason for using Tyvek type wall underlayments was more to stop air infiltration than water.

 

I tore a 3 y/o metal roof off that had Tyvek installed as an underlayment. The Tyvek had disintegrated into little pieces no bigger than a quarter. My guess is heat distress.

 

I've seen similar results behind vinyl siding, albeit the product has supposedly been improved over the years.

Any product will fail when pushed beyond what's reasonable. Proper flashing details and moisture management are crucial. The WRB is only part of the equation.

I'd put my money on a good flashing job with no WRB, before I bet on a WRB with no flashing.

 

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.

If it were a good second barrier, then why install I&W?

The underlayment (felt or other) serves all those purposes, whether under asphalt shingles or other roofing materials. How well it performs item #2 is a function of the roof slope, orientation, region, etc.

I&WS was not designed to replace felt, but to be used in areas where felt alone wasn't getting the job done (valleys, roof edge, etc.). Prior to the availability of I&WS, the areas where I&WS is used now were often hot mopped or two layers of felt were cemented together. I've also seen modified and 90lb used in trouble areas under slate and tile.

 

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.

 

I don't think you could pay a man enough money to walk on roof with tyvek. I don't care what the slope is.

 

This is one of those never ending debates.
Tyvek is proffered under siding with proper flashing due to its high perm rating and it's ability to block air.
Felt is proffered on a roof because you could walk in it and it sticks nicely to shingles. Permeability,as i mentioned earlier, is not a problem when you have a ridge vent with soffits.
If put on a wall, siding is not pressed against it like shingles are and any water it absorbes could cause it to curl and ultimately tear.
That's just my opinion.

 

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?

 

"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

 

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.