| Stucco Finish

Rized for its weather resistance, durability, and timeless beauty, stucco has long been one of the most popular exterior wall finishes. As a building material, stucco is essentially an exterior plaster made of Portland cement, sand, and water. Other ingredients may include lime, masonry cement, and various special additives for enhancing properties like crack resistance, workability and strength. With a few exceptions, stucco is applied much as it has been for centuries—a wet mix is troweled onto the wall in successive layers with the final coat providing the finished color and any decorative surface texture desired.

The two traditional stucco systems are the three — coat system used for standard wood-framed walls and the two-coat system used for masonry walls such as brick, poured concrete, and concrete block. And today, there’s a third process—the one-coat system— which allows you to finish standard framed walls with a single layer of stucco, saving you money and considerable time and labor over traditional three-coat applications. Each of these systems is described in detail on the opposite page.

The following pages show’ you an overview’ of the materials and basic techniques for finishing a w’all with stucco. While cladding an entire house or addition is a job for professional masons, smaller projects and repair w’ork can be much more doable for the less experienced. Fortunately, all the stucco materials you need are available in a dry preblended form, so you can be sure of getting the right blend of ingredients for each application. During your planning, consult with the local building department to learn about requirements for surface preparation, fire ratings for w’alls, control joints, drainage, and other critical factors.

Stucco is one of the most durable and low-maintenance wall finishes available, but it requires getting each stage of the installation right, as well as the mix of the stucco itself.

Tools & Materials ►

Aviation snips

Texturing tools

Stapler

Heavy-duty staples

I lammer

1 Ґ2" galvanized

Level

Roofing nails

Cement mixer

Self-furring

Wheelbarrow

Galvanized metal

Mortar haw’k

Lath (min. 2.5 lb.)

Square-end trow’el

Metal stucco edging

Raking tool

Flashing

Darby or screed

Stucco mix

Board

Nonsag polyurethane

Wood float

Sealant

Crade D building

Work gloves

Paper

Base Coat Stucco Calculator ►

Square feet

10

25

100

300

500

%" thick — # of 80-lb. bags

1

1

4

12

19

‘//’ thick — # of 80-lb. bags

1

2

6

16

26

Y«" thick — # of 80-lb. bags

1

2

8

24

38

All yields are approximate and do not allow for waste or uneven substrate, etc.

 

Stucco Systems ►

Three-coat stucco is the traditional application for stud­framed walls covered with plywood, oriented strand board (OSB), or rigid foam insulation sheathing. It starts with two layers of Grade D building paper for a moisture barrier. The wall is then covered with self-furring, expanded metal lath fastened to the framing with galvanized nails.

The scratch coat is the first layer of stucco. It is pressed into the lath, and then smoothed to a flat layer about %" thick. While still wet, the stucco is "scratched" with a raking tool to create horizontal keys for the next layer to adhere to.

The brown coat is the next layer. It’s about %"-thick and brings the wall surface to within 1/s" to V" of the finished thickness. Imperfections here can easily telegraph through the thin final coat, so the surface must be smooth and flat. To provide tooth for the final layer, the brown coat is finished with a wood float for a slightly roughened texture.

The finish coat completes the treatment, bringing the surface flush with the stucco trim pieces and providing the color and decorative texture, if desired. There are many options for texturing stucco; a few of the classic ones are shown on page 255.

Two-coat stucco is the standard treatment for masonry walls. This system is the same as a three-coat treatment but without a scratch coat. The base coat on a two-coat system is the same as the brown coat on a three-coat system. For the base coat to bond well, the masonry surface must be clean, unpainted, and sufficiently porous. You can test this by spraying water onto the surface: If the water beads and runs down the wall, apply bonding adhesive before applying the base coat, or you can fasten self-furring metal lath directly to the wall, and then apply a full three-coat stucco treatment.

One-coat stucco is a single-layer system for finishing framed walls prepared with a waterproof barrier and metal lath (as with a three-coat system). This treatment calls for one-coat, fiberglass-reinforced stucco, a special formulation that contains V" alkali-resistant fiberglass fiber and other additives to combine high-performance characteristics with greatly simplified application. This stucco is applied in a / to %"-ttiick layer using standard techniques. QUIKRETE One Coat Fiberglass Reinforced Stucco meets code requirements for a one-hour firewall over wood and form systems.

Texturing with Stucco ►

Finding the right blend of ingredients and mixing to the proper consistency are critical to the success of any stucco project. Premixed stucco eliminates the guesswork by giving you the perfect blend in each bag, along with mixing and curing instructions for a professional-qualityjob. All of the stucco products shown here are sold in complete form, meaning all you do is add water before application. Be sure to follow the mixing and curing instructions carefully for each product.

Scratch 4b Brown

Base coat stucco: Use this premixed stucco for both the scratch and brown coats of a three-coat application or for the base coat of a two-coat system. You can apply the mixed stucco with a trowel or an approved sprayer. Available in 80-pound bags in gray color. Each bag yields approximately 0.83 cubic foot or an applied coverage of approximately 27 sq. ft. at %" thickness.

Finish coat stucco: Use this stucco for the finish coat on both three-coat and two-coat systems.

You can also use it to create a decorative textured finish over one-coat stucco. Apply finish coat stucco to a minimum thickness of and then texture the surface as desired. Available in gray and white for achieving a full range of colors (see below). Coverage of 80-pound bag is approximately 70 square feet at /s" thickness.

One-coat, fiberglass-reinforced stucco:

Complete your stucco application in one step with this convenient all-in-one stucco mix. You can texture the surface of the single layer or add a top coat of finish coat stucco for special decorative effects. Available in 80-pound bags. An 80-pound bag covers approximately 25 square feet of wall at %" thickness.

Stucco and mortar color: Available in many colors, stucco and mortar color is a permanent liquid colorant that you blend with the stucco mix before application. Some colors are for use with gray stucco mix, while many others are compatible with white mix. For best results, combine the liquid colorant with the mixing water before adding the dry stucco mix, and then blend thoroughly until the color is uniform.

 

Attach building paper over exterior wall sheathing using heavy-duty staples or roofing nails. Overlap sheets by 4". Usually, two layers of paper are required or recommended; consult your local building department for code requirements in your area.

Install self-furring expanded metal lath over the building paper with staples orVA" galvanized roofing nails (don’t use aluminum nails) driven into the wall studs every 6". Overlap sheets of lath by 1" on horizontal seams and 2" on vertical seams. Install the lath with the rougher side facing out.

 

Install metal edging for clean, finished lines at vertical edges of walls. Install casing bead along the top of stuccoed areas and weep screed (or drip screed) along the bottom edges, as applicable. Make sure all edging is level and plumb, and fasten it with galvanized roofing nails. Add flashing as needed over windows and doors.

Use aviation snips to trim sheets of lath or cut edging materials to length. Cut lath and edging can be very sharp, so always wear gloves when working with these materials.

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