Tyvec or Tarpaper

scott2006November 20, 2009

Hello Everyone,

My handyman has called out a siding guy to take off my aluminum siding and replace it with Vinyl siding.

They are telling me that Tarpaper will last longer and do a better job for me over the long run and cost less.

I kind of feel like I'm taking a step backwards if I use tarpaper...?

I'm not too concerned with the cost...

The house was built in 1965, I have the black selatex material under the present aluminum siding.... if that matters.

Anyone have any comments on the above?

Thanks,

Scott

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macv

It's a toss up.

The only thing sub standard about asphalt saturated felt is the size of it's advertising budget (which is zero), a problem DuPont and it's competitors don't have.

If you use asphalt felt it should be No. 30 instead of No. 15 because the manufacturers stopped making it at 15 or 30 pounds per square a long time ago so the old 15 pound paper is now called No. 30.

If you use the wrap, stick to Tyvek, Typar or WeatherSmart because many of the other wraps are not waterproof.

    Bookmark   November 20, 2009 at 4:52PM
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scott2006

Macv,
Thanks for the reply.....we will go with the 30wt. paper.

Scott

    Bookmark   November 21, 2009 at 6:34PM
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drywall_diy_guy

I thought the object of Tyvec was to allow moisture to escape? Tar paper would seal the moisture in.

    Bookmark   November 21, 2009 at 6:58PM
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macv

Some common misconceptions about asphalt saturated felt underlayment are that it contains coal tar, that it is vapor impermeable, and that it is waterproof. The last two characteristics are true of synthetic roofing underlayments so they cannot be used on walls.

Asphalt saturated felt is as vapor permeable as some plastic house wraps but unlike plastic wraps, it gets more vapor permeable when in contact with water. However, it is not waterproof like the non-woven, non-perforated plastic wraps.

    Bookmark   November 21, 2009 at 11:32PM
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lonewolf20

But unless you tape the joints it won't stop wind penetration will it? And that would be a lot of tape.

    Bookmark   November 22, 2009 at 9:29AM
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scott2006

That brings up a good question....With the celatex under the tar paper or felt paper would the exterior wall be waterproof or should I not concerned with that?
Scott

    Bookmark   November 22, 2009 at 10:13AM
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macv

When the underlayment is exposed to water, Tyvek would remain waterproof longer and because of it's sheet size it would be a better air barrier but the Tyvek tends to be insalled with staples and that is not as good as roofing nails used with asphalt felt. Cap staples, screws or nails are best for Tyvek but more costly.

I have never seen house wrap properly taped. Tyvek tape was originally red and you could easily tell if it was improperly installed from the street. Now it's difficult to tell and contractors seem to never read the installation instructions. Most seem to think house wrap is just a modern version of building paper. Also builders rarely seal the top and bottom so the value of it as an air barrier is rarely what is claimed from controlled tests.

Whatever you use I would first tape any sheathing joints that do not occur over studs or spots that are damaged. That should be done with WR Grace Vycor Plus self-adhering flashing tape over WB Primer. the primer is essential for such a porous material.

If I had to choose a sheet underlayment for vinyl siding, I would use Tyvek CommercialWrap R with cap nails over the studs. But if your budget was large enough to afford commercial grade underlayment you would probably be able to afford real siding.

The very best underlayment would be a vapor permeable spray-on (or roller applied) liquid acrylic that is compatible with the surface of the sheathing. The sheathing joints and window openings would be reinforced with mesh tape and the result would be a continuous seal. That would be a real air barrier.

Here they are:

1. Perm-A-Barrier VP Air/Vapor Barrier fluid applied synthetic latex rubber membrane as manufactured by Grace Construction Products.

2. Air Bloc 31 as manufactured by Henry Company Inc., Cold Stream Road, Kimberton, PA 19442.

3. Sto Guard Assembly: manufactured by Sto Corp., Camp Creek Pkwy, Atlanta, GA 30331
a.Sto guard mesh for joints and flashings
b.Sto Gold Fill for joint treatment.
c.Sto Gold Coat for the membrane

4. PROSOCO R-GUARD Assembly: provided by PROSOCO, Inc., 3741 Greenway Circle, Lawrence, Kansas 66046.
a.PROSOCO R-GUARD Tape for joints and flashings
b.PROSOCO R-GUARD Fill for joint treatment
c.PROSOCO R-GUARD Spray Wrap for the membrane

    Bookmark   November 23, 2009 at 9:23AM
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rogerv_gw

Hmmm...I thought that vinyl siding was real siding? Live and learn, I guess.

I think that the main value of Tyvek-style house wraps is a continuous air inflitration barrier, to keep outside air from blowing around in insulation in walls and decreasing the value of the insulation. It will also shed water on the outside, and allow water vapor to go out from the inside of the wall so that it doesn't condense in the insulation. However, it is quite true that for the air barrier function you need to put it on in large pieces, and tape those pieces together so it acts as a single barrier for best use. I've also seen it applied like tar paper, and that's just sad.

At any rate, I like Tyvek, and would make sure that anyone that I hired to apply it knew how and why it is best used.

-Roger

    Bookmark   November 24, 2009 at 7:22PM
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macv

Vinyl siding is intended to simulate the appearance of wood clapboards therefore I guess it could be called real plastic imitative siding.

Don't confuse the function of Tyvek with that of a vapor retarder installed on the warm side of a wall in a cold climate.

    Bookmark   November 24, 2009 at 10:27PM
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kooshball

There is a very good article on the subject of moisture barriers here:
http://bct.nrc.umass.edu/index.php/publications/by-title/

Basically it explains that IF you have a water penetration with Tyvek and if that water gets on the wrong side of the barrier it is likely to stay there and cause damage. Tyvek blocks bulk water but allows vapor to move out of the wall but once you have bulk water on the wrong side of moisture barrier it will block that as well.

Macv is right; this stuff is almost never installed corretly to begin with and even less so on a replacement job so unless all your corner boards, trim boards, etc are removed and the sheathing completely wrapped you are likely to water at some point.

For me I will plan on the unplanned happening and go with felt paper; it meets the warranty requirements for the siding; works fine and if it gets compromised it will facilitate drying of the wall behind it

    Bookmark   November 27, 2009 at 8:48AM
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sombreuil_mongrel

IMO, Tyvek is best thought of as a wind barrier under vinyl. Live in a house without it and you will feel the difference. It's a nice secondary feature that it will not trap liquid water beneath it.
If you think vinyl siding is anything close to as wind-tight as a well-installed wood siding, think again. Vinyl siding is as drafty as an open window.
But tyvek alone will not guarantee a draft-free dwelling. You'd need to include additional measures like caulking the wall plates (before drywall); have perfectly-executed vapor barrier, and dead-on insulation (including foaming in the windows) to achieve that tightness, and in the end if you succeeded, you'd have to bring in fresh air through a heat exchanger so as not to have a "sick house".
Casey's post-turkey day musings.

    Bookmark   November 27, 2009 at 10:45AM
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macv

Tyvek will not trap water behind it unless water gets behind it and then it absolutely will trap it. Tyvek is a wonderful material but it is not as forgiving as asphalt felt. Install it well or pay dearly for your mistakes.

    Bookmark   November 28, 2009 at 4:35PM
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macv

Correctly sealing door and window openings has little or nothing to do with the choice of underlayment material.

The common approach of installing Tyvek first and wrapping it into the openings ignores the possibility that water can get behind the Tyvek and have an easy path into the openings. I like to install the windows and doors first and then the Tyvek or asphalt felt. Asphalt felt has always been installed in this manner and Tyvek provides alternate instructions for this method and WR Grace as well as Jeld-Wen recommend it.

    Bookmark   December 1, 2009 at 12:42PM
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