EIFS – How much drainage is enough

Because Exterior Insulating Finish Systems originally surfaced as a barrier system, water-resistive barriers were not required to be used in conjunction with EIFS when it first burst onto the Canadian market. EIFS seemed to function just fine as a water-resistive barrier themselves, and therefore no additional considerations were made.

Later, some areas of the southern United States began to experience water intrusion problems because of improper installation of the EIFS and nearby wall components. Unfortunately, EIFS was blamed for much of it and got stuck with a bad reputation for being a “leaky” wall cladding material. While undeserved, this gave birth to the use of EIFS with drainage, which is required in some areas of Ontario on buildings made of materials that may be susceptible to moisture. Some of these areas include Markham and Oakville, but much of Toronto can still use the barrier EIFS.


D2273 is the standard drainage test for EIFS as developed by the American Society for Testing and Materials, or ASTM. This test is used to determine the drainage efficiency of an EIFS with drainage wall, and this can be used to compare one type of EIFS with another, or other wall cladding systems.

D2273 does not determine how long it takes for the water to leave an EIFS wall nor goes it provide a standard of measurement for an amount of water retained that is acceptable or unacceptable. The drainage test is something you can recreate on site by cutting a hole in the top of a sample of EIFS and pouring water down in behind. Weigh the sample before and after and at separate intervals during the test, and you’ll be able to answer those questions yourself eventually, as you’ll be able to see how long it takes for the water to leave and how long the water is retained for.

Problems created by EIFS with drainage

Drainage cavities on EIFS also pose some problems. One of these problems puts the wall at risk during a fire. If fire travels up the EIFS wall, the gaps created by the drainage cavities can allow the fire to spread more easily.

Another concern relates to the one of the primary purposes of EIFS and a major EIFS selling point – its insulating properties and energy-efficiency attributes. Creating caps or spaces behind the EIFS lessens these attributes, and if someone takes it upon themselves to create larger cavities for better drainage, the effect on the insulating abilities of the expanded polystyrene foam becomes even worse.

The third and final concern is that when designing EIFS to be used with foam shapes, prefabricated panels or other special applications, drainage is not only difficult to incorporate, but difficult to incorporate effectively and correctly.

The most basic fact we can derive from this information is that the EIFS itself doesn’t leak. Water does not get into it, nor does it travel through it simply because it is an EIFS wall.

Drainage provides a “just in case” solution, but water intrusion really becomes an issue around adjacent components like windows or doors and at joints. Not only this, but in drainage EIFS the entire wall is suited with drainage capabilities, not just the base that is closer to the ground where it’s needed. If these components are installed or dealt with properly and drainage is used only where there’s a risk of leakage and at the edges, water intrusion won’t be an issue and using drainage across an entire wall only becomes necessary to appease building codes.

The easiest way to keep water intrusion from becoming an issue with EIFS walls is to design, engineer and build EIFS walls so there’s nowhere for moisture to get into the wall from the beginning.

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