Choosing the best stucco system generally means having sufficient knowledge to select a contractor who will provide a durable, attractive exterior for a “stick-and-stucco” house. Knowing the advantages and disadvantages of a stucco applications system can prevent expensive headaches later. Essentially, a stucco system begins with a waterproof “skin” applied over exterior sheathing to establish a drain plane. A special flashing called a weep screed is attached to the base of the outside wall, and flashing is secured around windows and doors. A metal lath skin attached to the wall holds the stucco until it dries.
Stucco is applied in three coats to the metal lath. Once cured, the stucco system provides a “stone skin” for your house. This is the traditional three-coat stucco system. Other stucco systems include a one-coat system and an exterior insulation and finish system (EIFS). To make an educated decision about a system or a contractor, details of these systems are important.
In the three-coat stucco system, practices vary. Some contractors use one layer of waterproof material, such as black felt paper or one of the newer synthetic wraps, shingled from bottom to top. Others recommend two layers of felt paper to improve the watertight integrity of the house. This is done with the knowledge that stucco will crack and, when it does, water will reach the drain plane, seep down the inside of the stucco wall and emerge from the weep screed. Two layers of membrane reduce the chance of mold in walls.
The likelihood of cracking can be reduced by waiting up to 45 days for a “weathered in” house to settle and any green studs to cure before applying stucco. Should cracks appear, a stucco repair system can be found wherever stucco supplies are sold. After a layer of metal lath is secured to the wall, three coats of stucco — brown coat, scratch coat, and finish or texture coat — are applied. Color is generally added to the final stucco mix and the final coat is textured to taste. Stucco products to add color are available at most building supply sources.
The one-coat system simply replaces the brown coat with a 1-inch (2.54-cm) rigid insulation board before the metal lath and the final two coats of stucco are applied as above. Although often included in the discussion of a stucco system, the EIFS is not truly a stucco system. It is a synthetic material that is virtually impervious to water and includes acrylic polymers. The EIFS is generally applied over an unbroken layer of polystyrene insulating board. Each EIFS is the proprietary product of a manufacturer, not a generic system.
A “barrier type” EIFS has the reputation of not “breathing" and releasing moisture as stucco does, and there has been controversy over some EIFS policies resulting in numerous lawsuits. EIFS manufacturers maintain that these problems have been eradicated. Careful investigation should be made before choosing a particular EIFS.