Stucco - Made to Last
Stucco gained popularity as a siding material in North America during the twentieth century, but it has been around for hundreds if not thousands of years. Modern stucco is made from a combination of cement mixed with water, sand and line, but in olden times the Greeks and Romans used stucco walls made from gypsum, marble dust and glue as a base for their beautiful wall frescoes. While nowadays stucco is rarely used for art it does have a number of practical features that make it an appealing choice for home siding. Stucco is hard, it resists water, is 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 DIY'er who is willing to take some time to create a long lasting exterior wall for their home.
Installing stucco is multiple step and time consuming process. First the walls need to be prepared and then the stucco itself is installed in three stages - a scratch coat, a brown coat and finally, the finish coat.
Wall preparation and Stucco installation
- 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 tacked firmly in place (to prevent moisture from getting into the wall), then over that a layer of 17 gauge, galvanized wire mesh is fastened. 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 applying the "scratch coat". This is a 1/4 to 1/2 inch thick layer of mortar spread with a masons 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 applying the scratch coat it needs to be allowed to partially dry for a few hours then using a "plasterer's rake" or a sharp piece of metal, scratch horizontal lines into the surface about 1/8" deep.
- Stucco needs to dry slowly so the scratch coat should be left to dry for a day or two while occasionally misting 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. Up to now all the stucco has been basically beige in color but 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.
Murray Anderson is an experienced freelance writer whose work has appeared on numerous web sites, in newspapers and books in both the US and Canada. He is often cited as an expert on home related topics.