Frequently Asked Questions
What stucco system is that?
There are three different stucco systems in common use:
- Exterior Insulating Finish Systems or EIFS
- Portland cement based three-coat or conventional stucco systems
- Portland cement based one-coat stucco systems
Let’s start with EIFS – What’s a typical EIFS wall assembly?
Typically EIFS is a layer of foam laminated or mechanically fastened to a substrate with mesh and a polymer base coat over the top of the foam, and then an acrylic finish over the top of everything.
What is a conventional stucco system?
Conventional – or three-coat – stucco will have a mechanically fastened weather barrier, or sprayed or rolled-on air and moisture barriers. Over the weather barrier will be expanded or woven wire lath, and then a portland cement scratch and brown coat. The finish can be a variety of products used individually – or in combination – to provide color and texture to the surface.
What is a one-coat system?
The weather barriers and lath for these systems are similar to three-coat stucco. Typically a one-coat system has a layer of foam insulation (referred to as continuous insulation) between the lath and the portland cement base coat.
Is a one-coat system really one coat?
In the 1970s, one-coat stucco was really one coat! By the 1980s, a topcoat was being used over one-coat. Many people started calling that system “two-coat.”
Do the building codes apply to these systems?
First there are broad national specifications to consider. EIFS and conventional stucco applications are part of the International Building Code (IBC). One-coat stucco systems have a third-party report from a model code agency as an application guideline. Manufacturers’ reports can be found on their websites or on the ICC website at www.icc-es.org.
What are hard coat stucco systems?
These are terms associated with one-coat and three-coat stucco systems They are described as hard coat systems because the base coats used for these wall assemblies are formulated with portland cement as the ‘backbone’ of the assembly.
What are water barrier systems?
The strategy behind water barrier systems is to never let any water past the cladding. In other words, when built right, the water never penetrates past the outer surface of the wall to the inner cavity where the moisture can affect the insulation and drywall. This is difficult but possible to do; however, once there is a failure, it can easily become catastrophic because large volumes of water can be trapped for an extended time before someone knows it: That can result in rot, mold, and expensive repairs.
What are water management systems?
Water management systems make the assumption that water will eventually work its way past the outer surface of the wall. But when it does, a system of flashings, weather barriers, and metal or plastic screeds will direct water back to the outside of the structure. All portland cement/hard coat systems – either one coat or three coat – are based on the ‘water management’ strategy. The SMA has additional information on stucco systems at: