Single-Ply vs Spray Foam: Which Roof Costs Less?

Upfront: single-ply may be less expensive. Over time: spray foam almost always costs less. Here's the complete picture.

Upfront Cost Comparison

New TPO installation: $5–$9/sq ft. New EPDM installation: $5–$8/sq ft. Spray foam restoration over existing roof: $4–$8/sq ft. For restoration projects, spray foam is often comparable to or less than single-ply replacement upfront — while also preserving the existing substrate and avoiding tear-off costs.

20-Year Cost

At year 20: Single-ply typically requires full replacement again ($7–$12/sq ft). Spray foam: recoat at $1–$2/sq ft. For a 50,000 sq ft roof over 20 years, that difference is $350,000–$600,000 vs. $50,000–$100,000 in ongoing costs.

40-Year Cost

Two full single-ply replacement cycles: $14–$24/sq ft cumulative. Two spray foam topcoat renewals: $2–$4/sq ft cumulative. The 40-year cost difference for a medium commercial roof can easily exceed $500,000 in favor of foam.

Energy Savings

Spray foam adds R-6.5 per inch — single-ply adds R-0. For buildings with inadequate roof insulation, the energy savings from foam can generate a compelling payback period of 5–10 years on the insulation premium, making foam cheaper even on a short time horizon in some applications.