What are the pros and cons of using spray polyurethane foam versus modified bitumen for flat roof reroofing?

Spray polyurethane foam offers cost savings, a seamless finish, and insulation, but needs UV protection and can be patchy if misapplied. Modified bitumen provides durability and weather resistance, lasting up to 20 years, though it’s heavier with visible lines. A Reddit r/Roofing user weighed these options, noting similar costs. Foam suits budget-friendly reroofing; bitumen fits long-term durability needs. A roofer’s input can refine the choice.