Synthetic stucco started out as a lifesaver. It was an economical, efficient version of stucco that was used in rebuilding structures after World War II, and it made its way over to North America during the energy crises of the 1970s. However, it also suffered from a tendency to not breathe -- in other words, it let water in (as real stucco can do, too), but it wouldn't let the water out. The lack of drainage led to severe rot problems in homes along the East Coast.

A newer form of synthetic stucco that was made to be more drainable is now available, though reactions have been mixed about its potential for success. If you want to use synthetic stucco for walls and trim and you also want to keep the structure dry and in good shape, there are ways to help keep that new drainage system working.

Keeping Water Out

Synthetic stucco lets water (e.g., from rain) into the wall, but so do other materials (that's why your house and office building don't repel raindrops). So since you already have that moisture getting in, you don't want to let more in. Ensure all other connections and seams, such as from chimney flashing, are watertight. Windows and door frames need to be properly caulked, though remember that if the trim around them is made of stucco too, the stucco trim will need to be able to let water drain out. Landscaping around the building needs proper drainage to prevent moisture from creeping upward in a wall.

Increased Interior Protection

When that water gets inside through the layer of synthetic stucco, it needs to stay away from the sheathing further inside the wall. Rather than relying on one layer of protective paper or felt, go for two (or more, if that seems good). The second layer protects the sheathing in case the first layer is defective, was installed improperly, or sustained damage that made it possible for liquid to get through. If stucco trim is installed on top of a stucco wall surface, remember to install drainage points along the bottom to increase air circulation and drying power. Water that soaks into the trim and can't drain out increases mildew risk.

Ventilating the Wall

It seems counterintuitive to add more ventilation to a wall that's supposed to be energy efficient -- wouldn't the ventilation make the wall less energy efficient? But this is a small trade considering the ventilation will let the intrusive moisture dry out and reduce the chances of the wall rotting. You must add a gap between the stucco and sheathing that allows for some air flow.

Stucco, be it real or synthetic, is a very good building material when used properly in construction. Stucco trim in particular looks very nice. But preventing rot in sheathing is essential, too, and it is best to ensure the installer is trained in the latest techniques for keeping everything dry.