How to Do Concrete Stucco

Apply stucco directly to concrete, concrete block, brick or other masonry surface. Prepare a wood-sheathed wall by covering the wood with a water-resistant membrane and metal lath, both fastened to the wood surface. Use a metal lath with small studs on one side, so they are held away from the sheathing, as this will ensure that the first stucco coat will penetrate and bind into the lath.

Install metal flashing around all windows, doors and other openings to prevent water from getting in behind the stucco. Position flashing in any area where water might get in. Put "weep screed," or a metal flashing with holes, at the bottom of the stucco wall. The weep screed is bent to go underneath the metal lath and direct any water that gets behind the stucco away from the wall.

Dampen masonry slightly before applying stucco. Use a prepared stucco mix. Add water, according to the instructions, as the stucco needs to be wet but not runny. Mix it in a tub or similar container, and put it in a mortar holder, or hawk. Use a flat mason's trowel with one straight and one notched edge. Rent a sprayer for large jobs. Stucco can be sprayed on, then finished with a trowel.

Use one of three stucco techniques. Traditional stucco is three-step process. First a base, or scratch coat is applied, followed by a brown, or smoothing coat. Lastly, a finish coat is applied with a trowel. The scratch coat is embedded in the lath, the second coat provides a smooth surface and the finish coat adds the desired color and texture. Some stucco is a two-step process: a scratch coat, then a finish coat. Some manufacturers offer a one-coat stucco that adds fibers and special chemicals to reduce the number of coats.

Spread the scratch coat with the flat side of the trowel, working it into the metal lath or pushing it firmly into the pores of the masonry. Cover the wall with a 3/8- to 1/2-inch thick coat, then "scratch" it horizontally with the notched side of the trowel. This will provide a good base for the next coat. Let it cure for 10 to 12 hours, then "hydrate" it by spraying it with water from a garden hose. Hydrate the wall one to three times, until the stucco retains moisture.

Put on a brown coat, 1/4 to 3/8 inches thick, and smooth it to a uniform surface like finished concrete. Hydrate it like the scratch coat, then apply a 1/16- to 1/8-inch finish coat to produce the decorative finish and color. Swirl or otherwise texture the finish coat to the desired look. Apply the finish coat the same day as the brown coat, so they will bond together. An alternative is to use an acrylic finish coat that can be spread over a dry, brown coat. Another alternative is to skip the brown coat and apply a thicker finish coat over the scratch coat.