An Honest Comparison: Single-Ply vs. Metal vs. Spray Polyurethane Foam

These three systems are among the most common commercial roofing options. Here's an honest comparison across the dimensions that matter most.

Initial Cost

Single-ply (TPO/EPDM): $5–$9/sq ft for new installation. Metal roofing: $8–$15/sq ft for new installation. Spray foam restoration: $4–$8/sq ft over existing roofing. For restoration applications, foam is the most affordable entry point.

Seams

Single-ply: heavily seamed — seams are the #1 cause of leaks and require ongoing inspection. Metal: seamed at panel joints, fasteners are leak points. Spray foam: completely seamless — no seams anywhere on the surface. Winner: foam.

Insulation Value

Single-ply: essentially none (R-0 for the membrane). Metal: essentially none (metal is a heat conductor). Spray foam: R-6.5 per inch — the highest of any roofing material. Winner: foam.

Warranty Renewability

Single-ply: replaced at end of warranty (full cost). Metal: replaced at end of useful life. Spray foam: recoated at end of warranty at $1–$2/sq ft — indefinitely renewable. Winner: foam.

Complexity Handling

Single-ply: requires custom fabrication at penetrations and transitions. Metal: seamed systems require custom flashing everywhere. Spray foam: conforms to any shape, sealing all penetrations and transitions in one application. Winner: foam.

The Bottom Line

For commercial roofing restoration, spray foam wins on seams, insulation, renewability, and complexity handling. Single-ply and metal have their place in new construction where foam isn't the appropriate primary system.