Anyone got a detail for using 2″ exterior rigid foam w/ stucco cladding?
mike keesee
| Posted in Green Building Techniques on
Working w/ a builder on a 3 story, multi-family where we spec’d 2″ exterior foam. The builder is using stucco cladding and to attach the stucco “chicken wire” they are using a metal z-clip that will go behind the foam, defeating the intent of the foam to elimate thermal brigding. Any help appreciated. thanks.
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Replies
Mike,
I have asked this questions multiple times in this Q&A forum. I have yet to see a solid recommendation.
Obviously the issue is fastening the lath to the framing through 2" of foam. I have never seen a stapler that shoots staples longer than 2 inches.
The only thing I can come up with is to use 3" screws with washers to catch the lath. Prepare for a lot of work.
There are washers that are made specifically for this application (Lath Lock Washers):
http://www.ebuildingproducts.com/catalog/lath-locklath-plate.htm
These, however, look a little excessive. (Actually I just confirmed the size-- only 1 and 1/4 inch diameter-- they looked bigger than that when I first glanced at the picture)
We have the perfect answer, StuccoMax is designed to adhere to ICF or foam with a standard mesh application. It is a 1 coat material. fmi see http://www.TheGreenBuildingProductsStore.com and look for StuccoMax. it will save a lot of time and money.
Mike,
As far as I know, must major stucco manufacturers provide their own details on how to properly install their product. You may try to go to their website and look for those details. Usually they come in PDF and DWG files. That was one of the important issues that came out of the stucco lawsuits in the 90’s.
Mike,
You have two choices:
1. Install a synthetic stucco (EIFS) system. Synthetic stucco is routinely installed over foam.
2. First install vertical furring strips over the foam, and then install traditional stucco over paper-backed metal lath fastened to the furring strips.
To all, thanks for the responses. Obiviously, this is an issue that needs to be addressed. I've forwarded to NREL to be addressed by a Building America Team. Hopefully the BA team willcome up w/ a detail soon. This is desperately needed in the field.
Mike,
While you wait on NREL, all the following issues you need to know should be spelled out in your stucco Manufacturer’s Specifications. (It's not as simple as it used to be)
The type of stucco lath you select depends on the kind of stucco application you are using, as in 1-coat vs 3-coat or EIFS, because of weight and thickness (Most of them won’t let you use “chicken wire” any more).
The type of fastener depends on the lath, stucco weight, thickness of insulation, pull-out-value, substrate type and thickness, framing members and spacing, and even your local climate and salinity for its coatings. Many of them conform to one or several standards, like ASTM or Codes like ICC.
In the SW, where we stucco almost every house, nobody installs stucco with furring strips, as they create a "bounce" in the stucco that creates a lot of problems. Every house uses double WRBs, like StuccoWrap or JumboTex 60, channeled insulation boards or applied WRBs, all per ICC. Again, that should be spelled out in your manufacturer’s specification.
All major manufacturer’s warranties depend on whether or not you follow THEIR OWN specifications, installation instructions and detailing.
You may want to download Win-Lock’s e-catalog, http://www.wind-lock.com/66/e-catalog.htm. They have fasteners for insulation thickness up to 5 ½” (page 6). They also sell lath locks, plastic and metal, as well as all sorts of laths, edges, joints, moisture barriers and tools for stucco applications, plus more. It’s a large file but worth having it as resource.
We have been using the products from http://www.trimtechnologies.com. It replaces the use of foam trim with wire formed shapes that end up solid after stucco. It is a "green" product. You will use less fasteners which is also a plus.