Walls & Ceilings Architect/October 2007

WIND Stucco is held to the wall structure with rigid fasteners and tough, st rong mater ia ls l i ke lat h a nd cement. EIFS is often attached using plastic washers or with discontinuous bands of adhesive to sheathing. Although EIFS walls can be designed to handle huge wind loads, the lightweight nature of the EIFS at tach ment system needs to be examined to be sure it can handle the loads. For low-rise buildings, like homes, this is rarely a problem, but in hurricane areas it can be. On the tops of tall buildings, especially at the corners where the loads are the highest, this load capacity issue and factors-of-safety need to be addressed. This is normally done by reviewing data provided by the EIFS producer that shows wind load capacities for various studs, spans, fasteners and sheathings. With EIFS, an adhesively bonded system on a strong substrate gives the strongest wall. The whole wall, including the stud connection to the building frame, as well as the sheathing and the sheathing fasteners, needs to be explored. EIFS brands and “approved equals.” With stucco you simply specify which of the many standard types of stuccos you want. In between EIFS and stucco are the many hybrid EIFS/stucco systems, most of which are proprietary and are also speciﬁed, like EIFS, as systems. those areas, beef them up with heavy reinforcing mesh, or protect the EIFS so that run-away shopping carts and lawn mowers can’t gouge them. VAPOR BARRIERS EIFS walls have the insulation outboard of the wall structure. Stucco has the insulation within the wall. The heat and water vapor f low through the wall changes depending on which system is used. In areas with extreme climates (arctic versus hot/humid, and extreme indoor activities, swimming pools, etc), the need for, and location of, vapor barriers, need to be considered. EIFS producers have computer programs that can analyze the wall and let you know what, if anything, is needed. JOINTS One of the big selling points with EIFS is that it can often be installed with very few joints. This requires a stable substrate that is also jointless. Stucco, due to its chemical nature and shrinkage during curing, needs control joints about every 144 square feet. If switching from EIFS to stucco, the elevations–and the location of control joints on them– need to be worked out. The location of the joints, where none existed before, can have a big effect on the appearance of the wall. With stucco and EIFS, if there are through-wall expansion joints in the substrate, then both stucco and EIFS need expansion joints there too; they can never bridge a working joint. THE FINALE All of the above considerations are not the only ones. But the key is to think about what implications there are for changing claddings– –how would your bid be affected? As they say, “The Devil is in the details”. Changing EIFS to stucco, and vice versa, is quite common, and doing so successfully is usually quite feasible. It’s simply a matter of thinking through the various issues involved (described above) and making allowances for the change. Often the difference in cost between EIFS and stucco is so close that the design is made more on the basis of energy savings and aesthetics, than on simply saving money. The oddest switch I’ve run into was a real deal-breaker: the owner wanted to switch from stucco to EIFS. The building was right on the lot line. When the foam was being installed, the neighbor raised hell about having the building on his land, and called out some surveyors. Rather than move the whole building, they switched back to stucco. W&C Robert Thomas is a nationally recognized EIFS consultant, based in Jacksonville, Fla. He was the manager of technical services for a major EIFS producer, is the author of several books about EIFS and chairs the ASTM committee on EIFS. INSULATION EIFS is an insulating system; stucco is not. Perhaps the biggest change when going from EIFS to stucco is the reduction in R-value of the whole wall. It’s easy to lose more than one half the R-value. This can necessitate adding a large amount of insulation in the stud cavity or other techniques to bring the total R-value up to energy code compliance. The reverse is also true: going from stucco to EIFS can increase the R-value substantially, perhaps letting you go from 2 x 6 studs to 2 x 4 studs. DRAINAGE Most codes now require that EIFS used on wood-frame buildings incorporate drainage into the EIFS. If switching from stucco to EIFS, on a wood frame building, a traditional barrier type EIFS may not be codecompliant, and EIFS with Drainage costs more and is slightly thicker. Also, the detailing is different, including water barriers, flashings, and so on. EIFS with drainage is usually about 20 percent more expensive than traditional barrier EIFS. GENERIC VS. SYSTEM Stucco is a generic product and is listed in the codes as its own building product. Countless books and specifications exist for various types of stucco. EIFS, on the other hand, are proprietary systems and are just starting to be fully described in the codes as a product type. When specifying EIFS, you do so based on specific HARDNESS EIFS is softer than stucco and does not take a beating as well as stucco. Sometimes EIFS buildings use stucco (with EIFS ﬁ nish as the ﬁ nal coat) at the on-grade areas for this reason, and a full EIFS system on the upper ﬂoors. If using EIFS, consider what areas may be impacted by people and objects, and if using EIFS in October 2007 | Walls & Ceilings Architect | 37

Table of Contents Feed for the Digital Edition of Walls & Ceilings Architect/October 2007

Contents Trade News Silver Certiﬁed Airtight The Men of Steel Thinking Thermal Firestop 101 ICFs Create a Tight Envelope The Finish Line The Green Thumb Cracking the Code

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.