Working with Stucco

Intro

One of the characteristics of stucco is that no two walls finished with it look exactly alike. Stucco allows you to create a one-of-a-kind surface. Applied properly, it will be maintenance-free for years.

Because it's a form of cement mortar, stucco dries to a gray color, but you can tint it by adding oxide pigment to the finish coat. To make white stucco, use white cement and white sand.

If you're going to stucco a house with siding, remove the siding and install felt paper and metal lath. To stucco a masonry wall, wire-brush any loose material and fill holes with patching concrete.

Some manufacturers recommend using a latex bonding agent so the first coat adheres more strongly to masonry. Be sure to use the bonding agent if it's recommended.

Apply the finish coat with a concrete finishing trowel, using long strokes. Keep the leading edge of the trowel only slightly raised for a uniformly smooth finish.

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What If ... The Stucco Goes on Wood?

To apply stucco over plywood sheathing, you'll need to give it something to grip. Staple 15-pound roofing felt to the sheathing, then cover it with metal lath. Cut the lath with aviation snips and fasten it with galvanized roofing nails. Lath has a top and a bottom. Install it so the metal vanes are angled up. Trowel on a 1/4- to 1/2-inch coat of mortar, forcing it into the lath.

Step 1

Hold a batch of stucco on a hawk -- a square platform with a handle on the bottom -- and apply it to the wall with a square mason's trowel. Apply the mortar with an upsweeping motion, working from the bottom up. Spread the mortar on the wall to a consistent thickness of 3/8 to 1/2 inch. Work in sections. Apply stucco to each section of the wall in the same way, always starting from wet mortar. Once you begin a wall, always complete it to avoid start-and-stop lines (called cold joints).

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Step 2

Allow the scratch coat (the first coat) to set up slightly, then ridge it with a plasterer's rake or a homemade scarifier, made by driving 4-penny galvanized nails through a 2-foot length of 2x stock at 1-inch intervals. Scratch the entire surface horizontally to a depth of about 1/8 inch.

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Apply the Brown Coat

Let the scratch coat cure. If local codes allow, you can apply the next coat (the brown coat) while the mortar is still wet. If the mortar has cured, mist it lightly. Using a flat trowel, apply a 1/4- to 3/8-inch-thick coat. Allow the stucco to cure for several days, misting the surface occasionally to slow the curing process. After it cures, apply the finish coat and texture it.

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Texturing the Finish

When the brown coat has cured, apply the finish coat 1/8 to 1/4 inch thick. Let it set up a little before you start any texturing.

Texture makes a more interesting surface. To start, experiment on an inconspicuous part of the wall to make sure you like the texture.

Begin texturing the finish coat as soon as it begins to set. Your texturing technique need not be complicated. You can create a coarse, uniform texture simply by making passes with a wood float. For a rougher finish, dab the stucco with a piece of carpeting that has a thick pile.

Textured or not, mist the finish coat frequently for several days in order to minimize cracking as it cures.

For a marbled look, push a stiff brush into the surface. Then flatten the high spots with a metal trowel, moving the tool back and forth in even strokes.

To get a spattered finish, load a paintbrush with stucco and strike it against a wood block, creating a stucco spray. To make the surface more uniform, spatter it again in an hour.

For an old-time overlaid finish, dab the stucco with a pointing trowel held flat on the surface. Pull up the trowel at an angle and twist it slightly to create edges across the surface.

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