Be a Brain about your Roof Membrane

Building owners often select single-ply membranes because they offer the lowest initial cost and require a relatively minimal level of maintenance. These systems are easily repairable in any season and can perform reliably for many years. While the roof construction cost typically represents only a small portion of total project costs, repairs resulting from roof membrane failure can be significant. In addition to repairing the roof itself, owners often face costly interior damage to finishes and building systems.

Moisture Intrusion and Installation Defects

Moisture intrusion is the primary cause of roof deterioration. Common issues include leaks at base flashings, improper installation at parapet walls, and inadequate head laps or backwater laps. Water should always flow down and over membrane laps, not against them.
In addition, insufficient application of membrane adhesive can compromise performance. During installation, using an inadequate number of fasteners to secure base sheets may allow high winds to cause billowing, leading to tears, seam separation, and ultimately water entry into the building.

Visual Inspection and Early Warning Signs

When visually inspecting a single-ply roof, the entire surface should be examined for cuts, punctures, tears, and moisture staining. If the roof feels soft underfoot, this may indicate moisture within the insulation or decking.
All laps and perimeter flashings should be carefully reviewed for separations, wrinkles, or openings, as these are common failure points.

Ponding Water and Drainage

Ponding water, regardless of roof type, will eventually lead to problems. Roofs are not designed to function as standing water reservoirs. Proper use of tapered insulation and crickets helps direct water toward drains. Persistent ponding can also void roof warranties, making proper installation and drainage design critical.

Perimeter Conditions and Edge Securement

Parapet walls and equipment curbs should be checked for potential moisture entry points and deteriorated or missing sealants. In many cases—particularly with low-slope roofing systems—proper attention to edge and perimeter securement is all that is required to prevent failure. Most roof blow-offs result from perimeter attachment failures, not membrane defects.

Long-Term Performance Through Maintenance

A healthy roof is a well-maintained roof. For new installations, careful attention to every construction detail is essential. For existing roofs, maintaining a program of routine inspections and maintenance will help ensure long-term performance and protect the building for years to come.

By Jonathan Stevens, Assoc. A.I.A., LEED AP BD+C