Commercial roofing in Florida City, FL

Low-slope roofs on multi-unit buildings depend on drainage. Florida's code sets a minimum design slope of one-fourth unit in 12, or 2 percent, for built-up, modified bitumen and single-ply roofs. In the HVHZ, no loose-laid ballasted or nonballasted system is allowed, and new decks need at least 1/4:12.

Florida City gets heavy rain. The 1991 to 2020 normal at Homestead General Aviation Airport is 59.90 inches a year. A low roof that holds water for more than 48 hours after rain fails the code's definition of positive drainage, and an overflow drain or scupper is needed where water could be trapped.

• Ask each bid to show the finished slope and where water drains.
• Ask whether an overflow path exists where a parapet could trap water.
• Ask for the product approval number for every membrane.

Compare bids on the same scope. Check that each one names the roofing system, the membrane standard, the edge metal test and the permit. A single-ply bid should cite ASTM D4637, D6878, D5019, D6754 or D4434, matching the material. A bid that cannot name its standard is hard to compare.

Roofing work in Florida must be done by a certified roofing contractor. A general contractor who does roofing must hold a roofing certification. Ask each bidder for its state license number and check it with the state before you accept a bid.

Florida's 25 percent rule applies to existing roofs. If the work is less than 25 percent of the roof area in a 12-month period, a repair may not need the whole roof redone. Confirm with the building office which part of the bid triggers full replacement.