Flat / Low-Slope Roofing Cost Calculator

For a typical 1,800 sq ft flat roof, EPDM rubber runs $9,000–$13,500 and TPO — the most popular option — runs $10,800–$15,300. Modified bitumen is the cheapest at $8,100–$11,700.

TPO is the most widely recommended for residential and light-commercial flat roofs — it's reflective (lowers cooling costs), seam-welded for fewer leak points, and mid-priced. PVC costs more but resists grease and chemicals better, useful for restaurant roofs.

Flat and low-slope roofs rely on a slight grade and proper drainage to shed water — standing water from clogged drains or an undersized slope is the leading cause of leaks and premature membrane failure.

If the membrane is still structurally sound with no major leaks, a roof coating ($1.00–$3.50/sq ft) can extend its life by several years for a fraction of full replacement cost — but it's a maintenance step, not a permanent fix.