Flat Roof Replacement Cost (Orange County, 2026)
| System | Cost per Sq Ft | 1,000 Sq Ft Roof |
|---|---|---|
| Modified bitumen | $4–$7 | $4,000–$7,000 |
| EPDM rubber | $4–$8 | $4,000–$8,000 |
| TPO | $5–$9 | $5,000–$9,000 |
| Silicone coating (restoration) | $2–$4 | $2,000–$4,000 |
These are installed prices including tear-off of one layer, insulation check, flashing, and permits.
What Drives Flat Roof Cost
Coating vs. Replacement: The $ Question
If your membrane is aging but structurally sound (no widespread wet insulation), a silicone coating at $2–$4/sq ft can add 10–15 years. That's potentially half the cost of replacement.
When coating works: surface aging, minor seams issues, still-watertight insulation. When it doesn't: saturated insulation, structural deck damage, multiple failed patches.
We evaluate this honestly on every flat roof — sometimes the answer really is coating, and we'll tell you.
TPO vs EPDM vs Mod-Bit: Quick Pick Guide
- ✓Want lowest energy bills? TPO (reflective white).
- ✓Want lowest upfront cost? Modified bitumen or EPDM.
- ✓Want longest track record? EPDM (50+ years of data).
- ✓Doing an overlay? Modified bitumen is often simplest.
Full comparison in our TPO vs EPDM vs modified bitumen guide.
Red Flags in Flat Roof Quotes
- ✓No mention of insulation inspection — the biggest cost variable, ignored
- ✓"We can do it in one day" for a full replacement — rushing flat roof seams is how leaks are born
- ✓No drainage discussion — if they don't talk about ponding, they don't understand flat roofs
- ✓Cash-only, no permit — unpermitted roofing voids warranties and creates resale nightmares