Stucco Trim 101: Your Guide To Stucco Methods And Application Process
Stucco is a type of cement-like coating that is placed over wood lath on buildings. Some of the stucco methods have been used for over a thousand years but were based on mud rather than cement. Today, it is still a very popular look and has expanded to multiple methods and styles. Stucco trim is not a fail safeguard against water, so drainage planes are required to keep any water from damaging the building.
What types of methods are used for stucco?
As mentioned above, there are several methods that are used for stucco.
Three Coat Stucco: This method is stucco applied an inch thick over the top of metal lath. The gap between the metal and the building is used for a weeping space. This allows water to seep out of the foundation.
Metal Lath Support: The stucco is bonded to metal lath and creates a bond to the wall. In most homes, the expanded metal lath is referred to as stucco netting because it is a galvanized wire that gets woven into a hexagon mesh similar to chicken wire.
Draining Plane: Made using building paper impregnated with asphalt, making it a material similar to fiberglass. It is constructed using two layers of the paper with one of the layers isolated from contact from any stucco. The space created from this is used as the draining plane and allows water to repel naturally.
How do you apply the stucco?
There are three coats of stucco that need to be applied.
Scratch coat: This coat is used to form a base for the following coats. Apply the coat to the structure and while it is still wet, score it with a trowel so it will bond properly with the following coat.
Brown coat: The brown is applied as soon as the scratch coat is hard enough to take it without cracking. A good rule of thumb is to wait at least two days before applying the brown coat. This coat will fill cracks in the previous coat while preventing new ones from forming. If for some reason there is a new crack that is longer than an inch, apply more to the brown coat before moving to the last step.
Finish coat: Let the brown coat sit for one to two weeks, depending on how much you want it to cure. This coat has more texture and perhaps even some color than the other steps. Since it is the final coat, this is the time to spruce things up and make it look good. There are a lot of color finish coats available to pick from these days. Using a coarse stucco trim finish can hide any cracks that would form, which will typically happen due to some shrinkage.
Want to try making your own stucco? All you need is Portland cement, water, sand, and a plasticizer – such as lime. If you mix the ingredients together properly, it creates a mixture that has a good tensile strength and will be weather resistant. The water has to be potable and the sand needs to be clean and high-quality.