Stucco

The Full Picture

Stucco is portland cement plaster used as an exterior finish. The American Cement Association describes it as made from cementitious ingredients and aggregate mixed with water, and says it is commonly attached to framed walls with metal lath or applied to concrete and masonry. On framed walls the build-up is typically a weather-resistive barrier, lath, then plaster coats. The classic three-coat system has a scratch coat, a brown coat and a finish coat, with a curing period between coats. Over concrete or masonry the lath may be omitted and fewer coats used, and some proprietary one-coat products exist. Color and texture come from the finish coat, which is often a factory-prepared product.

Stucco is often compared with EIFS (Exterior Insulation and Finish System), and the two are easy to confuse because both end in a textured, colored finish. They are different assemblies. Stucco is a cement-based plaster over lath or masonry and has no continuous foam insulation as part of the system, while EIFS bonds or fastens an insulation board to the wall and covers it with a reinforced base coat and finish. EIFS is also regulated differently: the EIFS Industry Members Association summarizes that IBC Section 1407 requires EIFS with drainage on framed Type V walls of R-1 through R-4 occupancies. An estimator who sees a stucco-looking elevation should confirm in the wall section which system is actually specified.

In the documents, stucco appears on the exterior elevations as a finish tag, in the finish schedule and in the wall sections and details, where the lath, backing, control joints and weep screed at the base are drawn. The specification is in Division 09 (Finishes), under plastering, and the weather barrier and flashing may sit in Division 07. Details to read include number of coats, finish texture, control joint spacing, accessories (casing beads, corner beads, drip and weep screeds) and any requirement for a mockup. Scaffolding or lifts for the work are often a separate general conditions or means-and-methods item.

The unit of measure is usually surface area. Traditional plastering is often priced per square yard (1 SY = 9 SF), while many contractors take off in SF and convert. Openings are commonly deducted, but returns at window and door jambs, soffits, reveals and decorative bands are added back because they are real plaster. Accessories are counted in LF, and lath and weather-barrier area is measured separately because it carries laps. Typical pitfalls are pricing finish area only and missing the lath, barrier and accessories, treating an EIFS bid as a stucco bid, and forgetting that each coat has cure time that affects the schedule.