One of the most popular home exteriors in the world is stucco. Cement-based stucco dries as an incredibly-strong, man-made rock material that will last for years. In addition, a well-maintained stucco home will increase in value because the maintenance is almost nil. This is because pigments can be added as it is mixed so that it never needs painting.
Traditionally, stucco was line, sand and water. This was used for centuries until the invention of Portland cement, a process whereby lime was burnt making it more durable when mixed with sand. These days fibers may be added for a one-coat system but most stucco contractors use a two, and even three, coat process.
Like drywall compound there are commercially-prepared stuccoes by using three parts sand, one part Portland cement and hydrated lime you can make your own a lot cheaper. The key to stucco is the the slower it dries the more it becomes.
Applying Stucco
Like plaster stucco usually needs a type of lath to hold it in place. The only time it doesn't is when it is to be applied directly to concrete but even here many contractors will put on a metal lath to be safe. On a wood surface the furred metal lath will be nailed on with furring nails right after the house wrap or two layers of tar paper. Because stucco is a type of concrete there must be expansion or control joints very eighteen feet. This will prevent cracking.. If the stucco is to be applied to brick or concrete wet the wall thoroughly and do not let it dry out. It would be safe to say that stucco should be applied in the shade so it will not dry too quickly but never below freezing.
Scratch Coat: The first coat is called the “scratch coat,†named so because it will be scratched by a broom to form small shelves or “keys†to hold the finishing coats. Like a plasterer doing laths the stucco is pushed through the metal lath to make “handles†but no thicker than 1/4†past the metal. This will provide the stucco a firm grip on the exterior of the home. The scratch coat will just cover the metal lath and then it will be whisked with the broom.
Brown Coat: The brown coat is the second preparation layer and will provide the base for the finishing coat which is the thinnest of the layers. The brown coat will be smoothed over the scratch coat filling in all the broom marks. This should be allowed to harden for 36 to 48 hours and it should also be kept moist.
Stucco Coat, or Finished Coat: This layer should be at least 1/8†thick to ¼ “ but any thicker and improper hardening may occur which could cause cracking. After 36 hours you can put on decorative coats for embellishment.
EIFS (Exterior Insulation and Finish Systems)
Synthetic stucco finish became popular after World War II because Europeans in bomb-damaged areas needed to repair structures made from stone, concrete and brick. In the 1980's EIFS gravitated to North America for use on commercial buildings because it was found to have a great R-value. To understand modern EIFS think of it as a multi-layered exterior with a stucco finish.
1) First Layer: A rigid foam insulation board is attached to the building with glue or screws.
2) Mid Layer: A Portland cement mixture is applied to the foam board and a a fiberglass mesh is pressed onto that.
3) Finish Coat: The compound and method of applying is just traditional stucco so the finish will be exactly the same.
There is a problem with EIFS when used on wooden structures because moisture is not allowed get out. Plywood, boards and oriented strand board have shown to rot because moisture can come in through cracks but not have a way to escape. Underneath the wood rots without an visible sign on the surface. However, with a concrete structure this is not an issue
Stucco and Cold Areas
Stucco is a great thermal mass for the home. It will refract the sun's heat in summer but in winter it will store it preventing the heat from the home from getting out. The biggest problem with having stucco in homes in northern areas is cracking from the freeze/thaw cycle. Fissures that appear will attract moisture that can freeze and make the crack bigger. In the southwest it is very cold but it is also dry so that the stucco will slowly get cold in the fall and winter and slowly get hot in the summer.
For more information on stucco contractors consult our Contractor Directory or post your project online and several contractors will contact you for a consultation on your project.
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