EIFS – more on EPS

Exterior Insulation Finish Systems usually get their insulating properties from expanded polystyrene foam, or EPS. All of the components of EIFS are sold as a system and have been developed and designed for specific purposes. EPS is no different, although EIFS-grade and non EIFS-grade EPS is available. The requirements EPS needs to meet when being used in EIFS are important to be aware of and to follow for a sound application.

Specifications for EPS when used with EIFS

The American Society for Testing and Materials has specifications on their website for EPS when it’s used with EIFS, known as C578. C578 assigns various density requirements to EPS, labeling the density used in EIFS applications Type I, which is the lowest density available.

The ASTM also has E2430, an extension of C578 that describes what’s required of EPS that is to be used for EIFS purposes. This extension makes calling for the proper EPS for use with EIFS much less complicated and provides more guidelines for installers when creating an EIFS wall using EPS.


Not all EIFS are created equal, because they are produced by different manufacturers. Therefore, not all EPS is equal and must be marked so it’s easily apparent which EIFS it works best with or is meant to be used as a component with. Typically the packaging EPS comes in is marked with the company and manufacturer names and any tracking information. Along with these requirements, at least one piece of EPS per set is to be stamped with the manufacturer’s information so it’s easy to trace it back to them if the need ever arises in the future. If the manufacturer’s name is on the wall and is readily available, no one needs to spend copious amounts of time playing detective and tracking down who made the product.


Imagine a flat piece of Styrofoam. Looking closely at it and you can see it is actually composed of tiny balls or “beads”, which are fused together to make a piece of Styrofoam. These Styrofoam qualities are similar to what is found in EPS even though they are not the same materials. EPS is composed of tiny beads as well, expanded into boards with gas during manufacturing.

One can snap a piece of EPS in a “fusion test”, breaking the EIFS in half to test the strength of EPS to ensure it doesn’t split when stress is placed on it by the lamina shifting. The goal of this test to see how strongly the tiny beads of EPS are fused together. Upon breaking the board, how many beads come apart from the board and fall to the ground, and how many of the beads themselves actually break in half along with the board? The beads themselves breaking in half are what you’re looking for in properly fused and strong EPS.


E2430 covers 1.0 pcf density for most EIFS applications, but higher density EPS might be able to be used for other related-purposes like foam shapes. Changes in density can affect cost, function and durability, and E2430 goes further to broaden the explanation on these requirements.


The pieces of EPS foam used in EPS must fight together extremely tightly, and therefore must allow for easy cutting without breakage so they can be trimmed to exact specifications.


E2430 requires EPS foam used in EIFS applications is aged properly. This means allowing the EPS that is fresh out of the mold to sit and rest for a while. If a block of EPS is cut too soon, it won’t stay flat when attached to the wall.

The EIFS Council of Canada also uses these specifications, which are in accordance with E2430:

  • EPS shall be aged and cut according to the requirements of ASTM E2430. Maximum size 600 mm x 1200 mm with a minimum thickness of 25 mm.
  • EPS will have a nominal density of 16 kg/m(1.0 P.C.F.).
  • EPS used in shapes and mouldings for decoration on EIFS shall comply with the above requirements.

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