www.mrca.org  —  Midwest Roofer
26
M
oisture exposure during 
construction delays is 
a familiar challenge for 
commercial roofing contractors, 
especially in regions like the 
Midwest where spring weather 
is unpredictable. Roof decks on new construction 
projects are often left exposed for days—or even 
weeks—due to unforeseen scheduling changes, 
material delays, or extended weather events. During 
this time, roof sheathing experiences multiple cycles of 
wetting and drying before a roof covering is installed. 
But how much does this exposure matter? What is 
really happening to the materials that lie beneath our 
roofing systems?
A new study led by Wiss, Janney, Elstner Associates, 
Inc. (WJE) aims to answer that very question. Titled 
*The Effect of Moisture on OSB and Plywood 
Sheathing*, this collaborative research effort with 
MRCA explores how moisture exposure affects the 
structural performance of common roof sheathing 
materials—specifically, oriented strand board (OSB) 
and plywood. The findings of the study will be unveiled 
during a featured technical session at the 2025 MRCA 
Conference and Expo, taking place Wednesday, 
October 22 at the Schaumburg Convention Center 
in Illinois.
This initiative represents the second phase of testing 
by WJE, building on a 2024 program that focused 
exclusively on OSB without the variable of moisture 
exposure. Phase 2 introduces plywood into the mix, 
allowing researchers to compare both materials under 
similar conditions. Full-scale test frames—constructed 
using 1/2-inch OSB and plywood—are currently 
By Megan Pope, MRCA Executive Director
TECHNICAL & RESEARCH
WHAT HAPPENS WHEN 
SHEATHING GETS SOAKED? 
PREVIEW OF A GROUNDBREAKING STUDY TO BE 
PRESENTED AT THE 2025 MRCA CONFERENCE

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