Stucco is an exterior home finishing plaster coat found on homes nationwide, thanks to its durability and versatility. The most popular types of house siding arefiber-cement panels,vinyl siding, and plywood. However, stucco has been used on houses for centuries and continues to serve homes well.
House exteriors are composed of many layers that work in conjunction with each other. The outermost layer is the mostvisible layerand the most important to the home's lifespan: the siding or cladding. Unlike other forms of siding, stucco applies equally well over masonry and wood-sheathed homes (though wood homes require a few modifications).
Sheathing is the material used to cover a structure's floor, wall, and roof framing. Wood-sheathed homes have sheets of wood products forming the exterior walls, which can then be covered with siding. House wrap and external insulation are often placed between the sheathing and the siding.
What Is Stucco?
Stucco is a cement-type mixture made of sand, Portland cement, lime, and water. Stucco is considered a thin"finish coat,"the outermost visible layer, and can be painted.
To make stucco work, you need layers below it to provide a good base. Today, it is not necessary to mix stucco from raw ingredients. You can buy pre-mixed stucco finish at most home centers that require only the addition of water.
Stucco Application Methods
Stucco is applied using one of three methods: one-coat, two-coat, and three-coat. They vary by composition, what surfaces they work best with, and speed of completion. One-coat methods are speedier, while three-coat methods are the gold standard and most durable. A three-coat method is best defined by its coats—the scratch coat, brown coat, and finish coat.
- One-coat method: Comprised of Portland cement, sand, fibers, special proprietary chemicals, and water; only requires a single application; can go over rigid foam board and lath
- Two-coat method: Used to coat brick and block walls; requires a bonding adhesive to keep the stucco adhered to the walls; the brown coat is eliminated, and the finish coat is applied directly to the scratch coat
- Three-coat method: Traditional method; can be used over wood sheathing or masonry surfaces; made of cement, sand, fiberglass, acrylic additives, and water; scratch coat starts with an asphalt-infused paper and a rough, scratched layer, next is the base layer or brown coat stucco, then a finish coat for texture and color
Stucco Finish Advantages
- Easy to customize: Stucco is tinted to add color to ensure colorfastness; it can be painted with ordinary exterior house paint; it can be textured in various ways, lending itself well to creative embellishments.
- Inexpensive: Stucco is considered one of the cheaper types of siding because it does not use expensive materials. Most stucco finishes are created from mixes; you can make your finish from raw ingredients.
- Resists moisture and inclement weather well: Stucco house finish provides an excellent seal against rain and snow because it is seamless, unlike nearly every other form of siding. Seams allow water and air into a home. Even seams that appear to be well-sealed may eventually open up.
- Long-lasting: Stucco is one of the most durable exterior materials, with atypical life span of 50-100 years or more, depending on environmental and climate factors.
- Resists fire, mold, rot, and termite infestations: Its composite materials naturally deter fire, rot, mold, and termites from invading the outer structure of a home. However, its rugged texture and porous spaces can provide small spaces for persistent mold to set in.
- Easy to maintain: It has one of the lowest annual maintenance costs compared to other siding materials. Maintenance usually involves inspecting the exterior and filling cracks. Because of its resistance to environmental factors (moisture, mold, insects, rot), it keeps maintenance needs to a minimum.
Stucco Finish Disadvantages
- Prone to impact damage: When hit, it can get damaged, and its crust will flake off; stucco's root word, "stucchi" in Italian, means crust or fragment, which explains how it crumbles.
- Professional installation and repair are recommended: Stucco requires mixing, color matching, and application with a trowel. Initial application and repairs are usually best left to the experts.
- Application requires time: Curing or drying for stucco requires at least 24 to 36 hours for each coat.
- Requires maintenance: It is easy to maintain but is not maintenance-free. You must inspect it regularly, patch cracks, and hose it down to keep dust and dirt from accumulating.
- Installation cost: Although the materials are cheap, the initial layout for professionally installing a stucco exterior to a house is time-intensive, bringing up the installation costs.
How to Apply Stucco
The steps you need to apply stucco depend on your choice of method—from one to three coats. You eliminate the scratch or brown coat in one- or two-coat installations. In general, the three-coat method includes the following steps:
- Apply bonding agent or stucco wrap: This layer acts as a stabilizing element for the plaster to adhere properly to wood, metal, or plastic lath.
- Apply scratch coat (base coat): Using a trowel, apply a 1/4- to 1/2-inch layer of the plaster. It may need up to 36 hours to cure.
- Apply brown or leveling layer: Once the scratch coat is dry, use a trowel to apply a second layer. It also needs to dry thoroughly before adding the last coat.
- Apply finish coat: After waiting another 36 hours for the brown layer to dry, apply the finish coat with a trowel, making the texture you want to be visible for the home's exterior.
- Paint: This step is optional; stucco can be tinted, not requiring paint. Acrylic latex is the better choice if applying paint.
Stucco on Masonry vs. Wood-Sheathed Homes
One prime place to install a stucco finish is over concrete masonry. Concrete masonry is stable and less prone to expansion, contraction, and other movements that may crack the stucco. While a stucco finish can be applied to a wood-sheathed home, additional reinforcement is needed.
Stucco on Masonry
On concrete masonry, little more than a scratch coat is needed below the stucco finish. A scratch coat is a base layer of cementitious material scratched horizontally with a comb-like tool.
Stucco on Wood
Wood-sheathed buildings require more preparation for a stucco finish than masonry buildings.
Wood sheathing itself will not provide a good base for a stucco finish. You must layer it with a house wrap or other waterproof building paper and then with self-furring metal lath. This lath provides the grip for the scratch coat to hang onto.
After the scratch coat, apply a brown coat to provide a smooth surface for the subsequent stucco finish.
The recommended thickness for the scratch coat for either masonry or wood-sheathed buildings is 3/8-inch minimum.
Can be textured as well as tinted
Materials are low-cost compared to other styles of siding
Tight seal against weather
Long-lasting when well-maintained
Repairs may need expert attention
Difficult for DIYers to install
Not appropriate for every locale
Easily chips and fragments upon impact
How to Maintain Stucco
The rule of thumb with stucco is to inspect your home's exterior for cracks regularly. Weathering may cause micro-cracks that can grow over time. Direct impacts may make holes. The beautiful thing about stucco is it's easy to patch, using paintable acrylic caulk to seal any fissures. Large holes or significant damage are best left to a stucco repair professional.
After repairing cracks, clean stucco walls once or twice a year to remove dirt and dust with a garden hose sprayer. Stains or algae can be removed with a dish soap solution or bleach-based cleaner. Refrain from using a power washer unless you use it on a low-pressure setting; too much pressure can introduce cracks and cause problems. You can use CLR (calcium, lime, rust) cleaner on unpainted stucco; refrain from using CLR on stucco that has been painted over.
Point away water sprinklers and gutter downspouts from stucco surfaces. Although stucco resists water, it's not impervious if cracks occur. Also, continuously introducing damp conditions combined with organic matter (dirt and plant life) invites mold and fungal growth.
Which is better, stucco or concrete?
Choosing between stucco and concrete comes down to its use. The two have a very similar composition, with the only difference stucco has lime in it, making it more breathable. This porosity makes it poor for weight-bearing but perfect for siding a home. It can be troweled on and adhere to vertical surfaces; concrete can only be poured or molded.
What is a cheaper alternative to stucco?
Fiber cement siding is also made of Portland cement but also includes fly ash and wood pulp and is formed into boards or shingles that resemble masonry or wood. It is a cheaper building material, easier to install, and requires less maintenance than stucco.
Does stucco add value?
Stucco that is well-maintained and in good shape may add value and curb appeal to a home.