Moisture issues in SIP roofs are typically caused by air leakage at joints leading to condensation. Repair requires identifying the specific entry point, replacing damaged OSB, and resealing with structural foam. If more than 15% of the roof is compromised, consult a structural engineer regarding total panel replacement.
Learn how to diagnose and repair SIP roof moisture issues. Discover why air-sealing and vapor management are critical to preventing structural rot in SIPs.
Repairing a SIP roof is complex and requires specialized knowledge of structural loads and building envelopes. Unless you have experience with high-performance building assemblies, it is best to hire a professional to avoid compromising the structural integrity of the roof panels.
The most common cause is the failure to properly seal joints between panels. This allows warm, moist interior air to escape into the panel assembly, where it condenses on the cold exterior OSB, leading to hidden rot and water dripping into the interior.
You should consider replacement if the OSB skin has significant rot, if the foam core is saturated with water, or if the roof shows signs of structural sagging. A professional structural engineer should evaluate the extent of the damage to determine if the panels can still safely support required snow and wind loads.
Airtightness is not the same as moisture-proof. If the panels were not sealed perfectly at the factory or the job site, air will leak through the seams. Once this air enters the assembly, the temperature difference between the interior and exterior causes condensation to form, which eventually drips.