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Stucco

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Intro
Stucco has been used in architecture for thousands of years. It is durable, relative maintenance free, and offers unlimited design possibilities Traditional stucco is a combination of cement, lime, sand and water. It is troweled by hand to the exterior walls. Traditionally stucco has been very popular in the southwest part of the country. Today stucco has become one of the most popular building covers in the past decade.

Today there are many different types of stucco systems. Traditional stucco is still popular but synthetic stucco is gaining in popularity. The main types of stucco used are: Traditional, 2 coat synthetic, and EIFS (pronounced "ee-fus") which stand for Exterior insulated finishing system.

Traditional
Traditional stucco is made of Cement lime, sand and water. It is still frequently used in the Southwestern U.S. Before stucco is applied, a building paper is attached to the exterior followed by wire mesh (chicken wire). Traditional stucco is applied by trowel in 3 separate coats. The building paper repels moisture, as water will pass through traditional stucco. The first coat is called a brown coat and is applied thick enough to cover the wire lath, usually about ¼" thick. the next coat is called a scratch coat because it is troweled on to a thickness of about 1/8" and then scratched with a rake like tool. The grooves created by the tool help the top coat to adhere to the scratch coat. The stucco is then painted to the desired color.

Two-coat synthetic
The two-coat synthetic stucco is prepared the same way as traditional stucco with a felt paper and chicken wire base. The brown coat is applied over the chicken wire the same as traditional stucco. The second coat or finish coat is then applied over the base coat. The difference is that the finish coat is made up partially of synthetics and fibers which make the stucco flexible and less likely to crack in seasonal climates. The color pigment is contained in the finish coat so that after it is applied no paint is required.

EIFS
EIFS systems have been very popular for the past 10-15 years, but have a troubled past. Many EIFS systems have failed in wet, damp climates, due to water penetration under the insulation board.
EIFS system start by gluing insulation board on the exterior of the house. Insulation serves the purpose of providing energy savings for the home and a waterproof envelope surface to apply the stucco. Two top coats are applied over the insulation similar to the two-coat synthetic stucco system. The EIFS system relies on the insulation board to keep out 100% of the moisture. In Dry areas or where the EIFS system is sealed well enough to keep 100% of the moisture from penetrating the enclosure, the system works fine. The problems is when water gets behind the insulation (through cracks, poor installation, or around opening such as doors and windows) the moisture has no means of escape, and wood rot is the result. Investigations found that some homes where moisture penetrated had begin to rot in less 2-3 years.
If the system is totally waterproof the system works well, however, it is becoming more evident that due to expansions and contractions of building materials that even a system that is water tight today may develop infiltration problems over time.
The real problem is that water will get behind almost any exterior system, so instead of trying to make a waterproof system the exterior surface should be designed to "breath" allowing trapped moisture to escape.

New EIFS systems
In the past several years there has been legal action brought against the major manufacturers of EIFS systems to address its short comings and to get compensation for homeowners with failed stucco. Because of the failing of the system and the legal action, most of the major manufacturers have now developed a "drainable" or "water managed" system that addresses water infiltration.
It should also be noted that homes constructed with concrete block or insulated concrete block system didn't suffer with traditional EIFS systems because there is no wood behind the insulation to rot.

 

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