Wall design and vapor barriers

[Vlab20]

We are designing a commercial building in northern California, 100 miles Northwest of San Francisco. The general contractor (from Wisconsin), who is our client in this case wants to use an EIFS system on the exterior. We have alot of information that the builders in CA do not want to touch EIFS and we are thus recommending using portland cement stucco. This is where the questions come: We are looking to design the wall with approximately 7/8" two coat stucco system on metal lath, over 30 # building paper, on 5/8" Dens Glas on 6 inch steel studs, with 6 inch fiberglass batt insulation and

5/8 inch Type X gysum wall board with permeable latex paint. I have been to Buildingscience.com but find that there is not a black and white answer to the wall design. Vapor Barrier needed? Vapor barrier on exterior of Dens Glass? Has anyone done any buildings in this Mixed Climate region or a Hot Dry Climate? I welcome any thoughts of details you have done on your projects. Thank you.

[3D Peruna]

You posted to alt.building.construction, too. Go to

All of the information you seek can be found there or through resources available there.

[nomail]

Traditional stucco on lathe usually requires three coats. Refer to your building code and ASTM C 926.

Depends on what you're trying to accomplish.

Is that the hot humid side in Northern CA?

[inspector.terry]

I do not know if the I-Codes are applicable, as only a few California jurisdictions are adopting a portion of the codes. So for what it may be worth, here is the IBC reference that may help.

2512.1 General. Plastering with cement plaster shall not be less than three coats where applied over metal lath or wire fabric lath and not less than two coats where applied over masonry, concrete or gypsum board backing as specified in Section 2510.5. If the plaster surface is to be completely covered by veneer or other facing material, or is completely concealed by anotherwall, plaster application need be only two coats, provided the total thickness is as set forth in ASTM C 926.

2510.5 Backing. Backing or a lath shall provide sufficient rigidity to permit plaster applications.

2510.5.1 Support of lath. Where lath on vertical surfaces extends between rafters or other similar projecting members, solid backing shall be installed to provide support for lath and attachments. 2510.5.2 Use of gypsum backing board. 2510.5.2.1 Use of gypsum board as a backing board. Gypsum lath or gypsum wallboard shall not be used as a backing for cement plaster. Exception: Gypsum lath or gypsumwallboard is permitted, with a weather-resistant barrier, as a backing for self-furred metal lath or self-furred wire fabric lath and cement plaster where either of the following conditions occur:

1. On horizontal supports of ceilings or roof soffits.
2. On interior walls.

2510.5.2.2 Use of gypsum sheathing backing. Gypsum sheathing is permitted as a backing for metal or wire fabric lath and cement plaster on walls. A weather-resistant barrier shall be provided in accordance with Section 2510.6.

Terry Combination Building Inspector ICC Certified Utah Licensed