EIFS Wall Drainage Systems Avoid Moisture & Mold Troubles - Best Practices Guide
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Stucco building exteriors: drainage plane, installation, 3-coat stucco, thin coat stucco, EIFS, stucco painting
EIFS drainage systems, products installation
EIFS wall success & workmanship
Sealants for EIFS wall systems
Questions & answers about the requirement & methods for installing wall drainage systems behind synthetic stucco wall coverings

EIFS Drainage systems: this article discusses in-wall drainage systems introduced to avoid moisture and mold problems in EIFS synthetic stucco wall systems, and the role of weather and moisture in stucco wall installation, durability, and painting success.

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Drainage Systems for EIFS "Stucco" Walls to Reduce Leak Damage

This article series discusses best practices construction details for building exteriors, including water and air barriers, building flashing products & installation, wood siding material choices & installation, vinyl siding, stucco exteriors, building trim, exterior caulks and sealants, exterior building adhesives, and choices and application of exterior finishes on buildings: paints, stains.

Readers should see STUCCO WALL METHODS & INSTALLATION, and also SIDING EIFS & STUCCO and STUCCO PAINT FAILURES and also may want to review POLYISOCYANURATE FOAM INSULATION. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

At SIDING EIFS & STUCCO and also cited at STUCCO WALL METHODS & INSTALLATION we discussed the history of leaks, water, mold, and rot damage that ensue when some EIFS wall systems were installed with details that permitted leaks into the wall structure. Usually these installations were not according to detailed manufacturer's specifications. Continuing from from Best Practices Guide to Residential Construction we discuss the introduction of drainage systems intended to reduce or avoid these EIFS difficulties.

Figure 1-30: EIFS Wall System Drainage (C) Wiley and Sons, S Bliss

This article series includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.

In response to these problems, most EIFS manufacturers have introduced new “drainage” or “water-managed” systems, which require the same type of waterproof drainage plane found behind traditional stucco systems (see Figure 1-30)

As with traditional stucco, layered building paper or plastic housewrap protects the framing and sheathing, and all exterior openings and penetrations are flashed to conduct any water to the outside of the sheathing wrap.

Since window leakage was the single biggest contributor to EIFS failures, pan flashing is recommended at windows.

Rather than gluing the EPS foam to the sheathing, the new drainage EIFS typically use mechanical fasteners and are designed with a capillary break between the back of the EPS and the sheathing wrap to promote drainage.

Some EIFS contractors use special corrugated or wrinkled sheathing papers to create the drainage space, while others have vertical grooves cut into the back face of the foam insulation.

In all cases, the drainage plane leads to a perforated weep flashing at the foundation to drain away any trapped water.

Workmanship & EIFS Exterior Stucco Wall Success

The backup drainage layer, however, should not provide an excuse for sloppy workmanship on the exterior skin. The new kinds of EIFS should still be made as waterproof as possible, since any water that leaks past the skin may be slow to dry out. EIFS consultant Russell Kenney, who has worked with these systems for nearly 20 years, recommends exceeding the minimum specs required by EIFS manufacturers.

On the other hand, 0ur EIFS damage photograph (left) shows how water or moisture traps can form in an EIFS wall even in a building interior, leading to substantial damage. (Photograph courtesy of home inspector John Rudy).

Kenney recommends a higher-density EPS foam with only 2% water absorption by volume instead of the 4% allowed by ASTM C584. In addition, Kenney recommends a heavier 6-ounce reinforcing mesh versus the typical 3-ounce cloth, as well as special high-impact mesh in high-traffic areas.

He also recommends a 3/32-inch base coat applied in two layers, with the first layer used to partially embed the fiberglass reinforcing and the second layer to fully cover and protect it.

These steps will significantly improve the impact resistance of EIFS, but it is still less durable than traditional stucco or thin-coat stucco.

See details about the cause, diagnosis, cure, or prevention of paint failures on stucco exterior walls, found at STUCCO PAINT FAILURES.

Apply Sealant to EIFS Base Coat

As with the original barrier EIFS, all penetrations require a high-quality elastomeric sealant. The sealant needs to be applied to the base coat since the finish coat tends to soften when wet, providing a poor substrate for sealant. For the caulk joints to last, they must be wide enough to tolerate the anticipated movement, typically 3/8 to 1/2-inch, and backed up by backer rod (see “Joint Design,” page 37 in Best Practices Guide to Residential Construction).

While control joints are generally not needed along the length of the wall—unless it exceeds 75 feet and is in direct sun—they are required between floors on multistory buildings. Silicone sealant is recommended at all joints for its longevity and flexibility in cold temperatures.

In theory at least, drainage EIFS should function the same as any other exterior cladding systems. Any water that manages to penetrate the outer skin should be stopped by the drainage layer and safely drained away. However, given the low permeability of polymer-based coatings and the tendency of EPS foam to soak up and hold water, EIFS are best avoided in residential projects unless high-quality workmanship and regular maintenance of sealants can be assured.

-- Adapted with permission from Best Practices Guide to Residential Construction.

Exterior Insulation and Finish Systems (EIFS) Resources & Suppliers

Dryvit Systems www.dryvit.com

Parex www.parex.com

Senergy www.senergyeifs.com

Sto Corp. www.stocorp.com

-- Adapted with permission from Best Practices Guide to Residential Construction.

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Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
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SIDING EIFS & STUCCO
  STUCCO EIFS DRAINAGE SYSTEMS
  SIDING EIFS WALL LEAK POINTS
  STUCCO OVER FOAM INSULATION
  STUCCO WAll FAILURES DUE TO WEATHER
  STUCCO WALL METHODS & INSTALLATION
    STUCCO RECIPES & APPLICATION
    STUCCO THIN COAT APPLICATION
  SIDING EIFS STUCCO FAILURES DUE TO WEATHER
  SIDING EIFS STUCCO PAINT FAILURES

Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Paul Galow - technical consultant on networking, LAN design, applications support. Galow Consulting Services, 914-204-1749, email: paulgalow@galowconsulting.com
John Rudy, Advantage Home Inspections, Flemington N.J. 08822 home inspector, 908-806- 6364, Home, Radon & Termite Inspections, Central & Parts of North New Jersey, email: jonadvantage1@yahoo.com
Malco® Products siding tools are available from that company, including the SideSwiper II SRT2 discussed at Malco's website. Websearch 09/07/2010 http://malcoproducts.com/product/roofing-siding-gutter/siding-vinyl/siding-tools-vinyl/sideswiper-ii. Malco also produces other vinyl siding repair tools such as aprons, awls, hole punches, saw blades, and tools for for fiber cement products including power-assisted cutters
Parmetol, a wood preservativerecommended by the manufacturer was used as a fungicidal additive to paint on the Blue Poplar wood sculpture in Amsterdam, by artist Mari Shields [ - art conservation consult DJF-artist MS 2010]
"Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
"Flashing: the plain solution to leaky walls", Thomas E. Remmele, Manager, Technical Services, Sto Corporation, Building Standards, November/December 1999 p. 21-25.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
Decks and Porches, the JLC Guide to, Best Practices for Outdoor Spaces, Steve Bliss (Editor), The Journal of Light Construction, Williston VT, 2010 ISBN 10: 1-928580-42-4, ISBN 13: 978-1-928580-42-3, available from Amazon.com
The Journal of Light Construction has generously given reprint permission to InspectAPedia.com for this article. All rights and contents are ©Journal of Light Construction and may not be reproduced in any form.
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Drainage Systems for EIFS "Stucco" Walls to Reduce Leak Damage

Workmanship & EIFS Exterior Stucco Wall Success

Apply Sealant to EIFS Base Coat

Exterior Insulation and Finish Systems (EIFS) Resources & Suppliers

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair