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No One Will Put It in Writing

Q: I’m documenting an EIFS forensic investigation where the sealants were applied to the finish coat and consequently the sealant failed. It seems the instruction that sealants should be applied over the basecoat of an exterior insulation and finish system, and not the finish coat, is not as well advertised as it should be. I’m looking for an authoritative statement that clearly declares that sealants must be applied to the EIFS basecoat. Where can I find this passage?

A: When I originally came to AWCI in 1999, one of the first education sessions I attended was the precursor to AWCI’s EIFS—Doing It Right® course. It was fairly new, and the facilitator was an industry expert named Dick Hopkins. Hopkins spent a considerable amount of time on this very topic because there had recently been a rash of EIFS problems that were rooted in moisture getting inside the wall cavity through a variety of avenues, and one of the primary avenues was a joint with missing or failed sealant. One of the problems that may arise when applying sealants to the EIFS finish coat instead of the basecoat is that the adhesion of the finish coat may not be strong enough to withstand the pulling force exerted on it by the sealant when the building moves. So, if the misapplied sealant causes the finish to let go from the basecoat—the same sealant that is intended to prevent moisture from entering the joint—the sealant also comes loose, and now moisture can enter the unprotected joint and do all the unfortunate things intruding moisture has become so famous for doing (rotting or rusting framing, fungal infestations, severe decomposition of the building components of the exterior wall and adjoining areas, etc.).

Much of the information offered in AWCI’s EIFS courses is based on the material found in ASTM C1397, Standard Practice for Application of Class PB Exterior Insulation and Finish Systems (EIFS) and EIFS with Drainage. So that is where I began to look for the actual official citable instruction stating something to the effect that “sealants shall be applied to the basecoat of an EIF system.” If only things were so simple.

ASTM C1397 covers just about everything one could hope for concerning the application of an EIF system, from the selection and inspection of the substrate material to the application of the finish and many, many steps in between. However, the application of sealants may or may not be performed by the EIFS installer and consequently is only barely mentioned in this standard. In the body of the standard, item 20.5 reads thusly: “Sealant Joints—The application of finish into the sealant joint is not allowed.” For more on sealants, one must go to the very bottom of the document to Annex A3, where there are five short statements that essentially refer the user to the design professional or the manufacturer for further information, but one line offers the following: “See Guide C1481 for guidance.” No slam dunk, but another lead that might produce the authoritative wording.

ASTM C1481, Standard Guide for Use of Joint Sealants with Exterior Insulation and Finish Systems (EIFS), sounds like a promising place to look for where one should and shouldn’t apply sealants in an EIF system. One might think that, but unfortunately, the closest the standard comes to spelling it out is in section 6.2.6: “The application of finish coat into the joint is generally not recommended by EIFS manufacturers.” There are several details in the standard that show the sealant affixed to the basecoat; however, there are several details where the finish could be construed to be under the basecoat, too. So, both consulted ASTM standards default to the manufacturer’s recommendations for finer details. Perhaps the manufacturers’ literature will be more definitive.

Sure enough, if one is inclined to dig through the manufacturers’ literature, he can find passages like these: “The preferred surface to seal to is the basecoat, not the finish coat.” and “Apply sealant to tracks or basecoat …” And finally, the details in EIMA’s installation guide offer this passage: “Note that sealant is applied to the reinforced basecoat and not to the finish coat.”

So, if there is a definitive, authoritative, citable instruction out there admonishing whoever is applying sealants in an EIF system to do so over the basecoat and not the finish, I was not able to dig it up. It appears that as with many things, one must check with the manufacturer’s literature beforehand, which nno doubt requires additional research when doing a forensic investigation.

Q: We are in the middle of trying to negotiate an Army Corps of Engineers Project where they are requesting very high STC ratings and will be testing many of our walls to verify compliance. Is there testing equipment on the market that would be relatively inexpensive and easy to use that we could test our assemblies with in the field as we go?

A: Seems the requirements for field testing sound levels are spelled out in ASTM E336, which refers to ANSI S1.4. There are two levels of gear in ANSI S1.4: Type 1 is for professional field testing and, as one might imagine, is a little pricey. Depending on sophistication, a hand-held sound meter available on the Internet ranges from $300 to $3,000. However, unless you’re required to certify the results, which probably means getting someone licensed to run the tests, you might get away with ANSI S1.4 Type 2 gear, which is far cheaper and easily available on the Internet. A hand-held meter in this category goes for between $80 and $300.

Lee G. Jones is AWCI’s director of technical services. Send your questions to, or call him directly at (703) 538.1611.

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