A1) I would use "Alternative materials, design and methods of construction..." per Section 104.11 of Appendix Chapter 1 to allow the use of one-coat stucco since Chapter 25 of the CBC does not address.
A2) I will accept current ICC Research Reports or last code cycle reports that are in the process of being updated.
A3) Not many companies have current (2006 IBC) reports available. By end of year, we should have a list available of current one-coat stucco products.
As a side note, the one-coat system may be accepted in California, but would not readily accepted elsewhere. Many believe the 3-coat is the best you can get. In some areas, they allow a modified 3-coat system that actually has the third coat applied the same day on the partially cured second coat.
The use of synthetic stucco over styrofoam with or without "chicken wire" is just a chicken's way of getting around using the term EIFS. Many areas will not allow EIFS over wood-frame construction. The historic problems ranged from adhesion to cracks, water penetration and finally mold because of the inability to breathe. This problem was increased by the documented poor installation of windows by unskilled personnel.
EIFS may not be allowed over wood-frame in many areas due to restrictions based on past problems (moisture related), performance and difficulty to ensure proper controls and application. Poor window installations become very obvious and contribute heavily to the problems. In the restricted areas, it is allowed on masonry walls since masonry have the ability to handle the moisture associated problems (mold, rot).
The 'one-coat' stucco system is actually a 2 coat process (1 base coat, which may be hand applied or mechanically applied using a plaster pump, and the finish coat, which can range in many different texture types and can either be job formulated (using cement, lime and sand), pre-blended 'stucco', or an acrylic based finish (as is used on the EIFS systems noted above).
'One-coat' stucco uses all of the finish types I have noted above, as well as the standard 3-coat (which, by the way, does NOT satisfy any required shear strength, although there ARE municipalities were increased nailing of the lath at the plate lines does satisfy this) and I agree that the 3-coat is a better system, with regard to strength and durability of the overall stucco system.
While the one-coat stucco does NOT offer quite the boost in R-values that some of the manufacturer's note (especially with the standard white expanded polystyrene, which tends to lose it's inherent insulative properties when left exposed to direct sunlight / UV - which is evidenced by the 'yellowing' of the foam, which some of you might have noticed - Although the extruded polystyrene, typically referenced as DOW foam, does perform much better and loses very little of it's R-value due to exposure), in some areas (such as Arizona) home builders are provided substantial tax credits for providing 'energy efficient homes', and as such it is they who specify the use of the one-coat system, and it is not simply a matter of the subcontractor attempting to 'cut corners'.
Likewise, as one-coat stucco can easily be applied by hand, it is better 'geared' for those areas where home building is more widely spaced, or sequencing does not allow for adjacent structures to receive stucco at the same time (as it is simply inefficient to use a plaster pump for much less than 300 sq yds of wall surface, and applying 3-coat by hand is grueling process). On many projects the one-coat stucco performed just as well as 3-coat, but what made the difference was the craftsmen, not necessarily the system.
Because of the potential undesirable performance of EIFS, some jurisdictions now have phased inspections of all stucco installations.