Commercial Roofing
What the exam tests
Commercial Roofing focuses on low-slope membrane systems, attachment methods, wind-uplift ratings, flashing details, moisture investigation, and repair-versus-replacement decisions. Questions often ask you to identify a membrane, explain how it is attached, and decide whether observed conditions are wind damage, workmanship, or age-related deterioration.
Core rules and concepts
- Slope and systems: low-slope is 3:12 or less. Common systems are EPDM (thermoset), TPO and PVC (thermoplastic), modified bitumen, built-up roofing, metal, and sprayed polyurethane foam with coating.
- Attachment controls response: fully adhered, mechanically attached, ballasted, and induction-welded systems distribute uplift differently. Identify attachment before judging damage.
- Ratings are assembly ratings: FM Global 1-60, 1-90, 1-120 and UL 580 Class 30/60/90 apply to the roof assembly, not just the membrane. Fastener type, deck, insulation, and edge metal all matter.
- Seams: TPO is heat-welded and should be probed; EPDM uses splice adhesive or tape; PVC uses solvent or heat welding. A seam opening may be wind damage or a workmanship defect.
- Perimeter and corners: suction is highest at edges and corners. Edge metal, termination bars, and curb flashings are common initiation points.
- Moisture: core cuts, infrared, and nuclear surveys locate wet insulation; they do not by themselves prove wind causation.
Worked example
A fully adhered 60-mil EPDM roof over insulation is reported damaged after a 95 mph wind. At the northwest corner, the membrane is peeled back, edge metal is lifted and deformed, and a splice seam has opened about 4 feet. The membrane elsewhere is well adhered, with no widespread blisters or wrinkles. Reasoning: the damage is concentrated in a corner zone where uplift suction is highest; edge-metal deformation and membrane peel are consistent with wind uplift; and the seam opening follows the peeled area rather than appearing as an isolated workmanship failure. Check the assembly rating, fastener corrosion, and adhesion condition, but the pattern supports wind damage rather than normal aging.
Traps that cost marks
Wrinkles, ponding, blisters, and foot traffic are common non-wind conditions. Ballast displacement alone may not damage the membrane. Do not call a seam failure wind damage without checking edge metal, attachment, and the direction of failure. Do not confuse a wet-insulation finding with a wind-damage finding.
Key points
- Low-slope is ≤3:12; identify EPDM, TPO, PVC, mod-bit, BUR, metal, or SPF before assessing damage.
- Attachment type controls wind response: fully adhered, mechanically attached, ballasted, or induction-welded.
- FM 1-90 or UL 580 Class 60 are assembly ratings, not membrane-only ratings.
- Perimeter and corner zones see higher suction; edge metal and seam failures often begin there.
- Wrinkles, ponding, blisters, and foot traffic are common conditions misread as wind damage.
- Core cuts and moisture surveys answer wet-insulation questions; they do not prove wind causation.