Commercial roofing in Lake Magdalene, FL

Most flat or low-slope commercial roofs in Florida use built-up, modified bitumen, single-ply or liquid-applied systems. For a new low-slope roof, the minimum design slope is one-fourth unit in 12, about 2 percent, for most of these systems. Ask each bidder to show the slope on the drawings and where water will leave the roof.

Positive drainage means the roof is sloped so water clears within 48 hours of rain. Florida rainfall here is heavy. Tampa International Airport averages 49.48 inches a year, and about 61 percent of that falls from June through September. A roof that holds water for a week in summer is holding far more than it was designed for in a dry month. Check that overflow drains or scuppers are part of the bid where parapets would trap water.

• Written slope and drainage plan, not only a material name
• Edge metal tested to the standard named in the code
• Single-ply membrane standard listed by ASTM number
• Whether the old roof will be torn off to the deck or recovered

Compare bids on the same scope. A bid that leaves out the old roof removal, the sheathing repair or the edge metal is not the same job as one that includes them. Florida law says a roofing contractor's scope includes required deck attachments and any wood sheathing or fascia replaced during the work, so ask whether those items are priced.

Check the contractor's status. A general or building contractor may not advertise as a roofing contractor unless certified or registered as one. Ask for the state license number and look it up before signing.