What a "flat" roof really is
Flat roofs aren't perfectly flat — they're built with a slight slope so water runs to the canales or drains. Over the years, settling, added layers and low spots can leave water sitting on the roof. A replacement is the chance to fix that slope.
Options
| System | Good to know |
|---|---|
| Spray foam + coating | Seamless, adds insulation, can build slope; needs recoating over time |
| TPO membrane | White, reflective sheets with heat-welded seams |
| Modified bitumen | Tough, layered asphalt membrane; often with a reflective coating |
See foam vs TPO for a closer comparison.
The parts that matter most
- Parapets — wrapped and sealed, caps repaired.
- Canales and drains — sized, sealed and kept clear.
- Slope — no low spots left to pond.
- Penetrations — cooler stands, vents and skylights flashed properly.
- The old roof — wet or rotten material removed rather than buried.
See flat roof replacement in Corrales.
Roofing questions
Can you go over my old flat roof?
Sometimes, if it's dry and sound. Wet insulation or rotten decking has to come out first.
Which flat roof lasts longest?
Each can last a long time when installed well and maintained. Foam needs periodic recoating.
Can you fix ponding?
Yes — foam can build slope, and other systems can use tapered insulation or crickets.