Commercial roofing in University (Orange County), FL

Low-slope commercial roofs in University need a drainage plan, not just a membrane. The code sets a minimum design slope of one-fourth unit in 12, about 2 percent, for built-up, modified bitumen, single-ply and liquid-applied roofs. A roof that holds water for long periods breaks down faster under this county's rain. Our arithmetic: Orlando International averages 51.45 inches of rain a year, so ponding matters.

• Ask whether the design includes secondary overflow drains or scuppers where parapets could trap water.
• Ask how the storm drainage was sized, since the plumbing code ties it to a 100-year hourly rainfall rate.
• Ask whether the bid assumes a tear-off to the deck or a recover over the old roof.

The 25 percent rule limits how much of an existing roof you can repair or replace in any 12-month period without bringing the whole roof system up to current code. Check the roof's own history before you assume the exception applies. A roof falls under it only if that roof was built, repaired or replaced in compliance with the 2007 Florida Building Code or a later edition, and the 2007 code took effect March 1, 2009. Confirm with the Orange County building office, because the answer depends on the roof's record.

Compare bids on the same scope: the same membrane, the same edge details, the same drain work and the same permit. A bid that omits overflow drains or tapered insulation is not cheaper, only incomplete. Ask each bidder to state the membrane standard, such as ASTM D6878 for TPO, so the lines can be checked side by side.

Ask for the roofing contractor's state certification or registration number and confirm it on the state license lookup. A general contractor who sells roofing work must hold a roofing certification, and a roofing sub must hold a state roofing registration. Check before any deposit leaves your account.