A single-ply membrane roofing system is designed to provide reliable, watertight protection for commercial buildings. But when moisture finds its way beneath the membrane, it can lead to serious issues, like insulation damage, mold growth, and costly repairs.
In this post, we’ll break down the most common reasons moisture gets under a single-ply membrane, and how to prevent it.
The seams of a single-ply membrane roof are one of its most vulnerable areas. If the seams aren’t properly welded, glued, or taped (depending on the membrane type) water can easily infiltrate the system.
Unlike built-up roofing, single-ply systems don’t have multiple layers for backup protection. That’s why redundancy and proper seaming are critical. A minor installation error at a seam could result in water entering the building envelope.
Prevention Tip: Always ensure your roofing contractor follows manufacturer specifications and uses certified installers familiar with the specific membrane type, whether it’s TPO, PVC, or EPDM.
Flashing is another common culprit when it comes to moisture intrusion in single-ply membrane systems. These failures can occur for a variety of reasons:
EPDM shrinkage: Over time, EPDM membranes can contract, pulling away from vertical surfaces and breaking the seal at the flashing.
Difficult penetrations: Odd-shaped penetrations, like square posts or wide-flange beams, make it challenging to properly flash with TPO or PVC membranes. Poorly formed flashings can allow water to enter.
Prevention Tip: Work with a contractor who has extensive experience in custom flashing details. Ask to see how they plan to install flashings around tricky areas and how those methods will ensure long-term waterproofing.
The success of any single-ply membrane roof depends on proper installation and a clearly defined scope of work. Inadequate specifications or shortcuts during installation can result in membrane damage, trapped moisture, and eventual system failure.
Make sure your roofing project includes the following:
A detailed scope of work and product specifications
Clear communication about how moisture protection will be handled at every stage
A high-quality single-ply membrane roof should keep your building dry for decades, but only if it’s installed correctly and maintained properly. Understanding the common causes of moisture intrusion can help you ask better questions, choose the right contractor, and make more informed decisions.
If you’re concerned about your single-ply membrane roof, or planning a new installation, reach out to our team for a consultation. We’ll walk you through your options and help you ensure long-term performance and protection.
Call us today or Request a roof inspection to get started.
