What is EIFS and What's New With EIFS?
EIFS (Exterior Insulation and Finish Systems), commonly known as “synthetic stucco”, have been growing in popularity over the past two decades. With fantastic design flexibility, architects love the aspects that EIFS offer, at a price that is competitive with other exterior claddings. EIFS are highly energy efficient claddings and have been tested by the Oak Ridge National Laboratory on behalf of the Department of Energy to be the best performing cladding available. Below is an overview of the application process of EIFS:
Aesthetically, there are several new finish options available to make your building stand out. With the design flexibility of EIF Systems, you can make an entire EIFS building look like it has several different claddings, such as cut limestone, granite, brick, old-world stucco and even metal panels.
EIFS Formed to Mimic Metal Panels EIFS Formed to Mimic a Brick Chimney
**The following guidelines are for informational purposes only and are not intended for use. This is a brief description as to what the general steps are for the application of EIFS. Actual application of any EIF System should be performed by a certified plaster/stucco contractor.
First, a secondary moisture barrier is placed over the substrate (if it is plywood or OSB – Oriented Strand Board). This is usually a product called Tyvek Stucco Wrap or a two-ply black asphalt paper (make sure that whatever you use is accepted by the manufacturer’s specifications and local codes). Newer technology has allowed for a liquid applied moisture barrier which is either roller applied or trowel applied onto the substrate.
Next, a Weep Member needs to be installed at the base of each wall to allow for drainage of any incidental moisture out of the wall cavity. This Weep Member is usually a type of plastic casing bead called Starter Track, or a corrugated plastic strip which furs out the foam to create a drainage plane.
At all terminations and around any penetration in the system, detail mesh (back-wrap) must be attached to the substrate. This is called “back-wrapping”. This back-wrap is the first step in reinforcing the edges of the foam sheathing (described in the next step), and thus the entire system at all terminations. The back-wrap is extended over the edges of the foam when it is attached to the substrate and is designed to reinforce the edges at the terminations/penetrations after the base and finish coats have been applied. It is very important that this step NOT be skipped.
Next, the foam sheathing is fastened to the substrate over the top of the moisture barrier. If your moisture barrier is in paper form (felt paper or Tyvek Stucco Wrap), the foam must be mechanically fastened. If it is a liquid moisture barrier, it must be adhesively applied. The foam sheathing comes in 2’x4’ sheets, and is usually in a 1” thickness. It can be as thick as 4” if desired, but no less than ¾”. Note: You cannot apply ¾” thick foam with mechanical fasteners, only with adhesive. As explained in the previous step, make sure that the back-wrap covers the edges of foam at all terminations and penetrations so that it folds over the front (exterior) section of the foam to be embedded into the base coat (as explained later).
Once the foam is in place to create the exterior envelope around the building, it is rasped, or sanded, to make the walls more uniform in case any of the foam is protruding or sagging. Also, rasping the foam better enables the base coat to bond to it.
Using a trowel, the base coat is then spread directly to the foam at 1/16” to 3/32” thickness. While still wet, the reinforcing mesh (a woven fiberglass material) is embedded into the base coat using a trowel. No mesh pattern should be visible through the base coat. If the pattern is visible, a thin layer of base coat should be skimmed over it to produce a smooth surface to receive the finish coat. To preserve the integrity of the system, all foam must be covered with a base coat and reinforcing mesh prior to the finish coat application. Allow the base coat to cure overnight prior to applying the finish coat.
After the base coat is fully cured and cleaned, the finish coat is trowel applied to the thickness of it’s largest aggregate, which is normally about 1/16”. This finish coat may also be called “color coat”, or just “color” or “finish”. While the finish is still wet, use a plastic float to “float” out the finish to achieve a uniform texture throughout the wall. Make sure not to let any of the finish dry or cure in the middle of a wall before that wall is completely coated. If you do, you will get what is called a “cold joint” that will be visible unless completely re-coated. Because this is an acrylic finish, it should NOT be applied any thicker than 1/8”. If it is applied thicker than 1/8”, it is susceptible to checking or cracking, and perhaps even de-lamination from the base coat. Also, if it is applied too thick, it is difficult to float out to the desired texture (unless you desire a heavy trowel texture).
There are several EIF Systems available, ranging from a glue-on "barrier" system all the way up to a pressure-equalized water managed system, depending on the requirements of the building owner. Design professionals should work closely with manufacturer's representatives to determine the most appropriate system for their clients' needs.
