Stucco walls have been common in hotter climates for centuries. Today, stucco is increasingly popular all over the world—a great way to add a finished, Spanish flair to exterior surfaces, covering unsightly, bare cement or concrete blocks.
A Brief History of Stucco
Stucco gained popularity as a siding material in North America during the 20th century, but it's been around for hundreds, if not thousands, of years. Modern stucco is a hard-setting plaster made from a combination of cement, water, sand, and lime. The ancient Greeks and Romans used stucco walls made from gypsum, marble dust, and glue as a base for their beautiful wall frescoes.
While stucco is now rarely used for art, it has a number of practical features that make it an appealing choice for home siding. Stucco is hard, it resists water, it's excellent at blocking wind and providing insulation, and it requires very little maintenance over its lifetime. Best of all, stucco can be installed by a DIYer willing to take some time to create a long-lasting exterior for their home.
Synthetic stucco has the same look as traditional stucco, and can even be more flexible from a decorative standpoint, but it's made up of layers including foam board, wire mesh, and acrylic paint. As a result, it admits very little air or water flow, making it better as insulation, but counter-intuitively worse as a defense against weather. If water finds a way behind synthetic stucco, for example, it can cause mold and rot on the interior surface. Synthetic stucco can be as durable as traditional stucco but does requires a little more maintenance.
A focus on the environment has brought many new innovative designs in green building. One of these is using straw bales in the construction of stucco homes. The concept has actually been around for over a century but has recently gained a new focus. The idea is that the stucco cement is placed on stacked bales of straw instead of the traditional metal wire. This makes the construction faster and more energy-efficient, and it uses a completely renewable source.
Installing Traditional Stucco
When applying stucco to a wooden wall, the first step is to cover the entire wall, either with 15-pound roofing felt or plastic house wrap, and tack the material firmly in place (to prevent moisture from getting into the wall). Over that, add a layer of 17-gauge, galvanized wire mesh. On concrete or brick walls, the first step is spreading a concrete bonding agent over the entire wall surface and giving it time to dry.
Once the walls are prepped, the next step is to apply the "scratch coat." This is a 1/4 to 1/2 inch-thick layer of mortar spread with a mason’s trowel. The mortar needs to be pushed down firmly into the wire mesh on wooden walls to provide a solid base for the rest of the stucco layers. After the scratch coat is applied, it needs to be allowed to partially dry for a few hours. Use a "plasterer's rake" or a sharp piece of metal, scratch horizontal lines into the surface about 1/8 inch deep.
Stucco needs to dry slowly. The scratch coat should be left for a day or two. During this process, occasionally mist it with water to prevent it from drying too quickly.
Once the scratch layer has dried, it's time to apply the "brown," or leveling, coat. This is a stucco layer applied directly to the scratch layer, then "floated" to create a smooth, even surface for the final coat. Once again, you need to allow the brown coat sufficient time to dry thoroughly before applying the finish coat.
The final coat is laid over the brown coat approximately 1/8" to 1/4" thick, then leveled with a finishing trowel. In the finishing layer, you can add colored pigments to give the wall a different color.
After applying the finish coat, allow it to dry slowly, again misting it occasionally to prevent possible cracking.
Maintaining Stucco Walls
The most important method for caring for any type of stucco is to periodically clean the stucco surface. You can easily wash the area clean with a garden hose and mild soap whenever needed.
Starting at the bottom of the wall, saturate the entire area with water until you get to the top, then keep a steady stream of water focused under the roof to dislodge dirt and debris. As dirt runs down, maintain that flow across the top until all the dirt is washed away.
Once the area is clean, inspect the wall for any damages or cracks. If any are found, they can easily be repaired with caulk or stucco mixture. Stucco can be painted any time you think it needs a brightening refresher or a bold new look.