Stucco is a very common material used on the exterior of a house or building. It can provide color, texture, and durability where other forms of siding can look rather bland. On the outside it looks fairly simple, but there is a strict regimen to follow when installing it that, if strayed from, can risk the structural integrity of the stucco. The three main components of a stucco system are the structural base, the base coats, and then the finishing coat.
The structural base of the stucco system is probably the most important piece of the puzzle. Traditional cement-based stuccos are vulnerable to cracking when movement occurs, so something has to be done to reinforce the entire system to prevent that from happening. That is where a metal lattice system, or metal lath, comes in. Metal lath is generally a sheet of metal with a matrix of diamond shaped holes throughout it that can also have dimples for extra gripping strength. It resembles a net or mesh and can be bolted or stapled right onto studs or concrete block and can easily be flexed to go around corners. This provides a structurally sound backboard that serves the purpose of providing a place for the stucco to adhere to as well as preventing it from flexing and cracking.
The next step to a stucco system is the base coats. It generally consists of two separate coats: the scratch coat and the brown coat. The scratch coat is the first coat to go on top of the metal lath and consists mainly of cement and sand in order to provide a coarse base for the system to grip to. The reason it is called a scratch coat is because it is then physically scratched with a tool in order to put grooves into it that immensely helps the next layer adhere to it. After the scratch coat comes the brown coat. The brown coat is a standard mortar mixture of cement, lime, and sand that is applied evenly and smoothly over the scratch coat. Once the brown coat is applied, leaving a little texture for extra gripping strength, the base coats need to cure for a week or so.
After the base coats are cured, it is time to put on the finish coat; the color and texture that everyone can see on the outside. There are two types of stucco that can be put on for the finish coat: an acrylic finish, or a standard cement-based finish. They both have generally the same aesthetics but there are a few advantages to each. Acrylic based stuccos are sturdier than cement-based and will guarantee uniform color throughout because they are pre-mixed by manufacturers in buckets. Cement-based stuccos on the other hand are a cheaper option that allows much more flexibility in texture and color, but requires more precise mixing of the materials.
It may seem like a simple installation when just seeing the finished product, but there is much more going on underneath the flashy colors and textures. Here at Landis Block we can provide your needs for all stages of the project from the structural base of the metal lath, the base coatings applied on top of that, and also both styles of finish coats. We carry Master Wall’s acrylic finish and the cement-based finishes from Penn Crete Stucco and Thoro Products.