EIFS and Synthetic Stucco

The terms EIFS and synthetic stucco are synonymous to many. Why discuss a synthetic coating in a blog about Real Finishes? EIFS systems have come to occupy a significant percentage of exterior cladding systems specified by design/build professionals in the United States. It is important to understand the contemporary architectural approach in exterior building cladding design utilizing EIFS to effectively articulate how traditional finish systems perform and compare.

It should be noted that synthetic stucco is only the finish component of an External Insulated Finish System or EIFS cladding and can be used in certain other non-EIFS applications. There are some variations in design; nevertheless, EIFS systems typically are comprised of the following components over an acceptable substrate:

1. A vapour/moisture barrier. This traditionally has been a commercial vinyl sheathing or felt paper. Some EIFS manufacturers are now producing a liquid barrier applied like wet paint that performs this function within hours of application.
2. An insulation board typically made of expanded polystyrene. Boards are usually affixed with an acrylic fortified cementitious paste by notched trowel. The lines of the paste are usually vertical to allow water to drain downward should it get behind the foam.
3. Another typically acrylic fortified cementitious paste is applied over the entire surface of the foam and a plastic mesh is embedded to give the coating strength.
4. Finally an integrally colored synthetic stucco is applied in a thin layer as a finish coat.
5. Many EIFS systems include a track running along the bottom with a weep screed (holes) that allow any water that were to get behind the coating to quickly pass out of the system.

Until the mid-20th century temperature and air quality in interiors were achieved by working in harmony with the surrounding environment. Orientation of the doors and windows, shading from trees and bushes, eaves and attic design were critical elements of construction. Inevitably moisture would make its way from outside and be generated from normal activities within the home. It was necessary to have breathable building systems that allowed moisture to find its way out.

With the industrialization that accompanied two world wars and the development of mechanical HVAC systems, building design changed rapidly. Now a building of virtually any shape could be placed on a cleared piece of land irrespective of shade or orientation. Electrically powered HVAC systems would guranantee a comfortable environment. The following two factors became of primary importance in modern building cladding design.

Most critical was waterproofing the building envelope. A cladding system that could effectively stop the passage of water and significantly restrict vapour flow was now favored over traditional coatings that "breathed", absorbing and releasing water and vapour. Advancements in synthetic material production resulted in highly effective water barriers for the market. HVAC would now regulate humidity and temperature.

A secondary concern was insulation. Mechanical systems were now the primary means to control temperature and they consumed electricity. Initially fossil fuel power plants could provide cheap electricity to meet the limited demand. But as more buildings were constructed with HVAC systems energy prices rose sharply.

EIFS, in continuous use since the 1960's, does a good job in addressing these two concerns of modern building design. When properly installed it provides a watertight wall system. The foam panels have significant insulative value and the membranes of vinyl sheathing or liquid applied coatings provide good barriers to the passage of vapour that would otherwise result in an adverse loss or gain of heat depending on the season.

Significantly because of these energy saving properties of EIFS it has been classified by some as a "green" building system. EIFS manufacturers have worked hard to reduce Volatile Organic Compound (VOC) content of their synthetic components, have localized manufacturing and use as much recycled content as possible to assure their products can contribute to Leadership in Energy and Environmental Design (LEED) accreditation for certain projects.

What makes a coating or building system "green" however? Energy savings? Sustainability of resources? Biodegradibility of materials? Environmental impact? Effects on indoor air quality and human health? That is the subject of a heated debate in the industry and will be repeatedly addressed in this series of articles as we compare coatings and systems.


Contributed by Patrick Webb