Stucco versus Synthetic Stucco
Doug Cox Advantage Construction & Closet System of New Mexico 505.471.1316 www.advconstnm.com
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hroughout the years working closely with my clients, I have noticed that many people know the difference between stucco and synthetic stucco, also known as EIFS, which is an acronym for Exterior Insulation and Finish System. However, there is some uncertainty in understanding the physical and chemical properties of the two products and the overall effect they have on the home. If you are building a new home or repairing the existing stucco or synthetic stucco on your home, there are important considerations to be made and procedures to follow so that you may avoid costly repairs should the product fail to protect the home from moisture penetration. Stucco is an earthen-based product composed of Portland cement, sand
and water with lime mixed in for workability. Synthetic stucco is an acrylic/ polymer-based man-made material. The permeability to water is the key difference between cement plaster and an acrylic-based material. There are other differences between their physical properties; flexibility, color retention, impact resistance and texture are some of these differences. Traditional cement stucco will absorb surface moisture and allow the moisture to evaporate out of the wall system through the transmission of water vapor. Synthetic stucco is a barrier type exterior cladding and is highly resistant to moisture penetration, which is a good thing when it comes to keeping moisture out, but this quality can create serious and expensive problems when moisture is trapped behind the wall and not able to evaporate out of the wall system. When synthetic stucco develops surface cracks, the moisture is trapped within the wall system and over time can start deteriorating the wall system from the inside out. The trapped moisture over an extended period of time may lead to serious mold issues that can be very costly to remediate. Indoor air quality can be compromised when moisture vapor is trapped inside the building. In humid environments where the ambient temperature inside a building can reach dew point – the point where
water vapor turns to liquid a result of temperature and pressure – the water has nowhere to escape if a water barrier such as synthetic stucco has been applied to the exterior siding of the building. Water collecting inside interior wall systems can go undetected for a period of time, which allows for the formation of mold growth. Building occupants are breathing mold spores before they know there is a problem, which can lead to serious and long-term health issues. There have been numerous law suits as a result of the EFIS system installed on buildings where there has not been a mechanical system in place to allow trapped water to drain out. Whether you are applying a three-coat cement plaster or a synthetic based polymer to the exterior of your home, how it is applied is critical to the success or failure of each of these products. Each manufacturer has their own set of details and procedures for installing their product, and builders and applicators are expected to follow their installation procedures or the manufacturer will not warranty their product should the material fail to do its job. Both stucco and synthetic stucco will develop cracks over the life of the product, so timely maintenance is important to getting 10 to 15 years of protection from moisture penetration from either cement plaster or an acrylic based plaster.