Synthetic Stucco Vs. Cement Stucco to Apply to an Existing Stucco House

Basics

• Synthetic stucco first appeared in post World War II Germany. The goal was to attach insulation to the exterior of the building, an alternative to applying insulation in wall cavities. Dryvit introduced EIFS in 1969. It was used on commercial buildings in the 1970s, but not on residential homes until the 1980s. Cement stucco is essentially a layer of fine-grained concrete attached to the exterior of your house. It has been applied to interior masonry surfaces for centuries, and beginning with the 19th century it was applied to exterior surfaces over laths.

Application

• Synthetic stucco is applied wet in two thin coats usually 1/16-inch thick over rigid insulation board fastened to a wall with adhesive or mechanical fasteners. Synthetic stucco dries as quickly as paint while cement stucco has to cure, a slow-drying process. Applying cement stucco requires a skilled plasterer and is generally more expensive to apply than synthetic stucco. You should repair existing cracks or broken sections of stucco before applying a new layer of stucco.

Disadvantages

• Moisture and water penetrating behind the exterior surface of synthetic stucco has led to problems with rotting wood. The National Association of Home Builders reports class action suits on behalf of homeowners who applied synthetic stucco on their houses and later experienced problems with wood rot caused by moisture trapped beneath the application. The water enters through windows, doors, seams and building joints because of bad caulking and poor or missing flashing. Because of the likelihood of moisture getting trapped under moisture, synthetic stucco was never intended to be applied on wood. Some companies will apply synthetic only as a finish coat after two layers of traditional stucco. The major disadvantage of cement stucco is that it can crack if the house shifts, often caused because the stucco was applied before the wood beneath it was allowed to dry completely.

Advantages

• You can mix synthetic stucco in any color you like and it looks more “modern” or clean than cement stucco, which is one reason why it is popular on business and commercial buildings. You can also apply synthetic stucco over trim, which you can't do with cement stucco. Cement stucco is hard, wears well, is easy to maintain, and it resists rot and fungus. You can color cement stucco with stains that penetrate masonry, but the range of available colors is more limited than those of synthetic stucco.