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Project Difficulty:
Difficult
Estimated
Project Time: Several days or more depending on drying time and size of project
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| Tools and Materials: |
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Ladder
Building paper, as needed
Spirit level
Pencil
Chalk-line box
Base strip
Galvanized nails
Hammer
Work gloves
Safety goggles
Metal shears
Steel mesh
Premixed stucco
Notched trowel
Scratch tool made from a 1x2 and galvanized nails (see Step 4)
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Stucco is made from portland cement, sand, lime, and water. You can mix your own or buy it premixed. Unless you're experienced, however, it's advisable to buy premixed stucco. Because stucco can be tricky to apply--and preparing a frame house for stucco installation can be time-consuming and labor-intensive--consider hiring contractors or at least one professional to work with you during application. A type of synthetic stucco system called Exterior Insulation and Finish System (EIFS) is also widely used for all types of residential applications. Only contractors, however, should apply the material; it is not a do-it-yourself job.
When you're about to begin the job, take care to choose an overcast day to stucco walls that have a southern exposure. Excessive heat can dry the stucco prematurely, which causes shrinking and cracking. Conversely, cool temperatures make the stucco too stiff for proper troweling. The ideal temperature for installing stucco is between 50 and 80 degrees Fahrenheit.
Two coats of stucco are enough if you're applying it to a solid, stable substrate like concrete block or other masonry walls (or over old stucco). On wood frames, however, you need to nail steel mesh to the sheathing over building paper, and apply the stucco in three separate coats. The top coat of stucco, if made using white portland cement, can be colored with pigments in a variety of earth colors. The texture results from the technique used to apply the finish. You can create a variety of looks by using different finishing tools (see Step 6).
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1.
Apply the Base Strip
If applying stucco to a wood-framed surface, cover the sheathing with building paper. Most stucco installations are anchored with a base strip. To set the strip, make level marks at corners, and snap a line in between. Then set the base strip along the level line and fasten it to the wall through the mesh portion of the strip using galvanized nails. (Fig. 1)
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2.
Attach Steel Mesh
Above the base strip, fasten sheets of steel mesh to the surface. Extend the bottom edge of the first sheet onto the base strip. Hold the mesh in place using galvanized nails. (Fig. 2)
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3.
Apply the First Layer of Stucco
Prepare the stucco mix following the manufacturer's specifications. Using a notched trowel, spread a layer of stucco onto the surface, exerting enough pressure to set the mix into the weave of the steel mesh (Fig. 3). This first layer of stucco is also known as the scratch coat and it should be about 3/8-inch thick.
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4.
Scratch the Surface
To maintain a bond between coats, scratch the surface of the first layer before it hardens (Fig. 4). A homemade scratch tool will do. To make the tool, drive nails through a length of 1x2, spacing the nails evenly and about 1 inch apart. If application of the second coat is delayed, keep the scratch coat moist by water-spraying it periodically. After that, you can let it dry out, as long as you dampen it just before applying the next coat.
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5.
Apply the Second Coat
Spread a second layer of stucco; this is also known as the brown coat and it should also be about 3/8-inch thick (Fig. 5). Its purpose is to furnish a uniformly smooth finished plane and provide uniform plaster suction over the entire surface. It can be applied to the scratch coat as soon as the scratch coat has set enough to support the added weight (from a few hours to a few days, depending on weather conditions). If not applying a third coat, the scratch coat and the brown coat should be applied thicker to create a 7/8-inch total thickness, the surface of which can then be textured (see Step 6).
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6.
Apply the Third Coat
Moist-cure the second coat for at least 48 hours and let it dry one or two days before applying the third coat of stucco. In most applications, this layer of stucco is only 1/8- to 1/4-inch thick; it is also referred to as the finish coat, top coat, or color coat. For a smooth texture, trowel on the stucco, and then finish it by passing a wood float over the surface. To produce a dragged finish, scrape a piece of 2x4 down the surface. To create swirls in the texture, pass a trowel back and forth making short arcs in the stucco. (Fig. 6)
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