2003 Morrison Hershfield Report

Assessing the Impact of Thickness on the Performance of Stucco Cladding

William C. Brown, P.Eng., Mike Dietrich, P.Eng., Mark Latimer

This is an interesting technical paper done by Morrison Hershfield Ltd. They were retained by the Alberta Housing Industry Technical Committee (AHITC) to develop a professional opinion on whether 15 mm, two-coat stucco cladding would provide performance equivalent to that of code-compliant three-coat stucco. The field study however, unexpectedly identified quality-control concerns with the installation of stucco cladding.

This report caused the AHITC to withdraw their request to have the Alberta Building Code changed.

Lets check out some of the highlights (lowlights) of the 13 page document. (If you would like a copy, it can be obtained at the Morrison Hershfield website ):

• The field investigation of stucco cladding in Alberta found that 85% of the applications were thinner than the current Building Code.
• 57% of the stucco applications were thinner than the proposed thickness of 15 mm;
• More than half of the two-coat stucco applications surveyed would require maintenance or repair within five years to maintain functionality.
• Repairs were rarely observed. However, those that were observed were typically unsuccessful as the cause of the damage, usually excessive wetting, had rarely been addressed.

As a result of the study, Morrison Hershfield recommended that a quality-control program be established to address design, workmanship and materials issues related to stucco cladding. In the postscript is an excerpt from the Alberta Home Builders Association which states that "AHITC started work on an action plan to improve building envelope workmanship in Alberta"

So they worked for two years and came up with: The Stucco Toolkit!