Ah wind loading, one of my favorite subjects. The IBC defines "hurricane-prone regions" as areas subject to basic wind speeds greater than 90 miles per hour, such as the East Coast. The code also defines a "wind-borne debris region" as an area hurricane-prone where the basic wind speed is 110 mph or greater. The code states that if a building is located in a wind-borne debris area, the window glazing must be impact resistant or protected by an impact resistant covering.
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: