The Problem With Moisture Buildup in Wooden Parapets

By Dani Sheehan. 

Learn from the leading technical authority at WSRCA on wooden parapets and how to mitigate condensation potential. 

In a recent episode of Roofing Road Trips, Megan Ellsworth sits down with Kenneth Klein from the Western States Roofing Contractors Association (WSRCA) to discuss his latest paper on the condensation potential within wood-framed parapets. A member with Western States for the last four years, Ken has been with Simpson Gumpertz and Heger for 38 years, specializing in waterproofing, building envelopes and roofing. He was brought into WSRCA for the technical bulletins he develops and other technical input when needed. 

His latest bulletin focuses on wood-framed parapets and the potential for condensation buildup. Unfortunately, many roofers are accused of using failed roofing membranes, when design can affect this problem equally and roofers have little to no control over that. He wanted to bring attention to the issue to help in improving the design of these systems and inform roofers since they are always the first to receive a phone call. 

To help highlight the problem for those that have not read the paper, he starts by explaining condensation as a volume of air that holds a certain amount of moisture depending on warm or cold temperatures. He further explains, “So I’m showing you a sponge right now, and as it gets cold, you might squeeze out water. So this volume of air that gets in the cavity of a parapet all of a sudden gets cold because there's no way to keep it warm at night.” When the moisture level in the parapet exceeds 19 percent, it can lead to mold buildup or deterioration of the wood over time which will ultimately break down the structure. 

Rest assured, there are precautions you can take to help mitigate this problem. Ken emphasizes, “The bottom line is, you don’t want air from the building or the structure to get up into the parapet.” He provides solutions such as sealing off the cavity or ensuring ventilation by using vapor-permeable underlayment.  

Listen to the full podcast to learn more about solutions for condensation buildup and find access to technical resources on a variety of roofing topics.