Portland Cement Plaster (Stucco),
One-Coat Stucco and EIFS - All Differ

Portland cement plaster (stucco) is the conventional exterior finish covered by code. One-coat stucco systems and EIFS are considered alternates to conventional stucco and are covered by evaluation reports issued by different code bodies.

Each is different from the others. There is a gross misunderstanding of the fact one-coat stucco systems are NOT EIFS - exterior insulation and finish systems.

One-coat stucco systems are comprised of building paper, a substrate such as 1" expanded polystyrene, or sheathing, covered with 20-gauge stucco netting or metal lath and 3/8-inch of enhanced portland cement plaster produced by the one-coat stucco manufacturer. A manufacturer approved finish coat completes the job.

One-coat stucco systems incorporate those elements that the manufacturer feels will enable the system to perform as well as conventional stucco. Proprietary elements may include glass or polypropylene fibers, and perhaps some kind of polymer the manufacturer believes will assure satisfactory performance. Naturally, proprietary elements used are not divulged.

EIFS is an entirely different system, using polystyrene panels up to four inches thick, over which a thin adhesive basecoat of usually acrylic modified portland cement is applied, followed by embedment of glass fiber mesh fabric, followed by a reliable elastomeric coating. EIFS manufacturers specialize in EIFS.

Performance of all systems is predicated on protecting interiors of buildings from the elements. Each system has its own requirements. Where these requirements are conscientiously implemented, the systems perform excellently.

John Bucholtz, P.E. - Techniques & Comments