Up Front: Bits and Pieces
Focusing on the impact resistance, if the glazing is located in the lower 30 feet of the building, the glazing must be able to pass the "Large Missile Test" of ASTM E 1996; where they shoot a number of 2x4s at the window and evaluate the results against the acceptance criteria. For window glazing located above the 30-foot level, the "Small Missile Test" of ASTM E 1996 is called for, which is a procedure that involves shooting small steel balls at the window and evaluating the results.
With that stated, there follows an exception that allows you to ignore all of the above if the components and cladding are designed, according to code, as a "partially enclosed building," as opposed to an "enclosed building." What does that mean? Well, without going into it too deeply, it means the building's internal design pressure increases by a factor of approximately three.
If we consider a wind pressure to be positive when it acts toward the wall and negative when it acts away from the wall, then a negative internal pressure will add to the positive external pressure and subtract from the external negative pressure and a positive internal pressure will subtract from the positive external pressure and add to the external negative pressure. Got that? Don't worry about it-I too have to draw a sketch to keep things straight. The bottom line is making a last minute decision to go from impact to non-impact resistant changes the design loads on all of the wall components and cladding.
So what's the problem? The problem is whether the component and cladding designers know that the loads have changed. This new information may not make a big difference to a project with a concrete frame, CMU infill and partitions, etc., but it makes a big difference to a steel stud infill or steel stud panel project of which there are a number of along the Southeast Coast.
I apologize for the abrupt change. In my almost never-ending quest to dissuade the use of the term "synthetic stucco," I offer the following: It confuses the consumer. It is also my opinion that stucco is not just a "look," as often claimed, although from a distance the stucco finish and the EIFS finish do sometimes appear to be similar and/or the same. However, beyond the finish layer the systems are quite different. The Portland Cement Association offers the following on its FAQ's Web page:
Question: Are plaster, stucco and EIFS the same?Answer: We are often asked if stucco and plaster are the same thing and if plaster and EIFS are the same thing.
The answer requires a thorough explanation. Plaster is the more general term for material that is applied to a wall surface in a thin layer. Portland cement-based plaster is such a material that uses Portland cement as the binder. It is sometimes called "traditional stucco." Stucco is a somewhat colloquial term for Portland cement plaster and some people consider it to refer to an exterior-not interior-finish. EIFS stands for exterior insulation and finish system, which is sometimes (incorrectly) called "synthetic stucco." To complicate matters, "plastering" is the verb that describes the action of applying any of the various materials to a wall surface.
The answer goes on to explain the difference between Portland cement plaster and EIFS, which is consistent with my statement above that concludes by stating that the systems are quite different. The PCA also says that Portland cement should not be confused with EIFS although they share similarities in application and final appearance.
EIMA does not have a position because, as the association says, it has never acknowledged or recognized the term in any way, shape or form. The Carolinas Lathing and Plastering Contractors' Association position is that it does not recognize the term "synthetic stucco" as being synonymous with EIFS. I will continue to build my case.