Quote:
Originally Posted by BrianL99
I suspect it's EFIS or Dryvit, which are synthetic "stucco" products, usually backed by something like DensGlass sheathing.
DensGlass holds the highest "mold resistant" rating available under ASTM D3273. Vastly superior to most any other sheathing product. It is not "styrofoam".
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Exterior Insulation and Finish Systems (EIFS), invented by the Dryvit company in 1969, made possible a lot of interesting “stucco” buildings with attractive molding details. It was originally spread over expanded polystyrene. It became very popular for businesses, as it allowed good insulation plus sealing out moisture. The problem was that a lot of builders failed to read or follow the instructions, water got under the nearly impermeable outer skin, then couldn't get out, resulting in serious mold problems. This staggered the industry, as many of these rotting buildings were under warranty. I believe this was especially a problem in southern Florida, forty years ago. Perhaps better building methods have helped, along with use of DensGlass insulation, but if so, the key concept is "Keep it dry!" in residential construction, whether stucco or EIFS, a major place water gets in is around the edges of window frames. The detailing there must follow the instructions carefully. water has a good chance of entering in climates where rain runs down walls a lot, like here, and lawn sprinklers hitting the walls is a problem.
"Real stucco" has for many decades been several coats of concrete spread over metal lath nailed or screwed to the wooden studs. this has been the preferred building coating in California for nearly a century. One feature is that the color (usually a pastel) is mixed in with the top coat of concrete, so it NEVER NEEDS PAINTING. In California, many stucco houses nearly a century old have never been painted. In the presence of humidity or rain, real stucco sucks up moisture a bit, then releases it when the moisture stops. But if you paint it, you seal the concrete, perhaps keeping moisture out, but also sealing moisture in. thus, humidity inside a house, say from cooking or showers and baths, gets into the walls but cant permeate out through the stucco. Careful use of exhaust fans can help. But people, with real stucco, don't think you need to paint it. If the concrete is stained, you don't need to. However, it may be that painters here are spraying the stucco with special stucco stains that don't seal the concrete.