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View Full Version : House Wrap with Stucco - Tyvek or Typar??



rduncan
05-21-2006, 11:22 PM
I am just starting a new project that will have a stucco exterior finish. Tyvek stucco wrap is available and I have read the product specs. Does Typar have similar characteristics??? Any other recommendations regarding house wrap for stucco finishes? Thanks for your suggestions.

Sweep8
05-23-2006, 12:12 PM
Typar is much less vapor permeable than Tyvek and it seems a bit tougher. Tyvek StuccoWrap is wrinkled to provide a drainage plane. Be sure to use two layers of underlayment behind stucco since the stucco can adhere to the underlayment and prevent drainage. Two layers of Typar might reduce the vapor permeability below what you want for your climate. Some people suggest the layer against the sheathng be Tyvek HomeWrap (or StuccoWrap) and the layer on top of it be a cheap perforated housewrap. Others recommend two layers of #30 asphalt building felt. Be sure to bring the underlayment out over a weep screed at the bottom.

Roger P
05-23-2006, 05:43 PM
I agree with Sweep8. Tyvek StuccoWrap is NOT intended to be used under stucco. It was developed for use in EFIS. This is a marketing faux pas by some MBA at DuPont.

IRC 2003
R703.6 Exterior plaster. (Read stucco)

R703.6.1 Lath. All lath and lath attachments shall be of corrosion-resistant materials. Expanded metal or woven wire lath shall be attached with 11/2-inch-long (38 mm), 11 gage nails having a 7/16-inch (11.1 mm) head, or 7/8-inch- long (22.2 mm), 16 gage staples, spaced at no more than 6 inches (152 mm), or as otherwise approved.

R703.6.2 Plaster. Plastering with portland cement plaster shall be not less than three coats when applied over metal lath or wire lath and shall be not less than two coats when applied over masonry, concrete or gypsum backing. If the plaster surface is completely covered by veneer or other facing material or is completely concealed, plaster application need be only two coats, provided the total thickness is as set forth in Table R702.1(1).
On wood-frame construction with an on-grade floor slab system, exterior plaster shall be applied in such a manner as to cover, but not extend below, lath, paper and screed. The proportion of aggregate to cementitious materials shall be as set forth in Table R702.1(3).

R703.6.2.1Weep screeds. Aminimum 0.019-inch (0.48 mm) (No. 26 galvanized sheet gage), corrosion-resistant weep screed or plastic weep screed, with a minimum vertical attachment flange of 31/2 inches (89 mm) shall be provided at or below the foundation plate line on exterior stud walls in accordance with ASTM C 926. The weep screed shall be placed a minimum of 4 inches (102 mm) above the earth or 2 inches (51 mm) above paved areas and shall be of a type that will allow trapped water to drain to the exterior of the building. The weather-resistant barrier shall lap the attachment flange. The exterior lath shall cover and terminate on the attachment flange of the weep screed.

Stuccoman
05-23-2006, 06:18 PM
I have been told cement/masonry should never come in contact with tyvek.

Sweep8
05-24-2006, 12:29 PM
Building Science Corporation Principal Joseph Lstiburek said:

"The Vancouver problem was due in part to the lack of drainage between the hardcoat stucco and the building paper drainage planes. Papers remained bonded to the hardcoat stuccos. Water stayed in the system, and the building papers (as well as other things) deteriorated. It seems that the more recently manufactured building papers don't work as well as the old stuff in that they don't debond as easily. Unlike Seattle, where two layers of paper were common, only one layer was the norm in Vancouver. No drainage space means no drainage. No drainage means big trouble--Rot City.

Now let us replace the building paper in a hardcoat stucco application with Tyvek. The hardcoat stucco bonds to the Tyvek. Water stays in the system, because there is no drainage. It passes through the Tyvek in vapor form as well as by capillary transport. The problem gets worse. The Tyvek loses its water repellency due to the surfactants in the stucco. At least with the impregnated or coated paper you stand a chance. Sometimes the paper debonds, sometimes it doesn't. If you're smart, you use two layers of paper and the system pretty much works. You stand no chance at all with Tyvek by itself.

DuPont's StuccoWrap product isn't much better. That's because the hardcoat stucco bonds to the StuccoWrap and therefore the assembly does not drain. StuccoWrap was developed for exterior insulation and finish systems (EIFS), where foam separates the StuccoWrap from the synthetic stucco skin. In an EIFS assembly, StuccoWrap performs spectacularly. But put hardcoat stucco directly over StuccoWrap and the drainage is compromised.

Having said that, I actually love StuccoWrap. When I put a layer of building paper over the StuccoWrap in a hardcoat stucco application, I get fantastic drainage between the back of the building paper and the front of the StuccoWrap. This is the approach of choice, in my opinion, for hardcoat stucco applications. Now replace the building paper over the StuccoWrap with a cheap perforated plastic housewrap and it gets even better. Put the assembly over OSB and the system just rocks!

The best possible system money can buy with hardcoat stucco is DuPont's StuccoWrap under a perforated plastic housewrap. The worst is hardcoat stucco directly on Tyvek or hardcoat stucco directly on StuccoWrap."

Personally, I prefer the first system he recommended: #30 asphalt building felt over Stuccowrap, but the important point to remember is to avoid single layers of underlayment behind stucco.

Allan Edwards
05-24-2006, 06:54 PM
I always use at least 2 layers, Stucco Wrap and Fortifiber, been known to use 3. I've been told (and don't know if it's true or not) that with self furring lath, the scratch coat actually pulls away from the wall a miniscule amount as it dries, creating a capillary effect.

Stuccoman
05-24-2006, 09:35 PM
Yes allan it does some what! But the makers of these wraps wiil do what ever it takes to sell their products. When they are testing them to get the ER report if one test does not meet their needs they try another till one does! What good do all these products do when the OSB has a perm rateing of 1.?

kinchyle
05-25-2006, 01:20 PM
Building Science Corporation Principal Joseph Lstiburek said:


Personally, I prefer the first system he recommended: #30 asphalt building felt over Stuccowrap, but the important point to remember is to avoid single layers of underlayment behind stucco.

Would this apply to cultured stone applications?

Stuccoman
05-25-2006, 01:24 PM
Imo Yes! It is the same!

rduncan
05-31-2006, 08:41 AM
THANK YOU to all that responded with technical information, experiences, and suggestions.