Nearly all residential homes being built today have pitched, or sloped, roofs. This allows rainwater to run downhill, into gutters, through downspouts and away from a home’s foundation. Quickly channeling water off a rooftop eliminates the potential for pooled water, which can lead to problems like mold and algae growth, wood rot and deterioration of roofing materials.

Most commercial buildings, however, have flat roofs. Why is that? It’s because their large square footage and design wouldn’t allow for a slope at the same angle as a single-family home. The roof would be too high, as well as costly.

Despite their names, flat roofs aren’t precisely horizontal to the ground. For drainage purposes, the International Building Code requires a minimum 2% slope, or a one-fourth unit vertical for every 12 units horizontal. In layman’s terms, that means a roof must slope ¼ of an inch for every foot. It’s a minimal slope, barely noticeable to the naked eye, but enough to allow gravity to do its thing and send water off the roof.

Flat, or low-slope roofs, offer a variety of benefits for commercial buildings:

  • Cost: A popular roofing material used in flat roofs across Southwest Florida is TPO (thermoplastic polyolefin), a single-ply membrane that covers a roof structure rather than shingles, tiles or metal panels. TPO is adhered or mechanically attached to a structure and costs less than other roofing materials. Because crews take less time to install TPO, commercial entities can save on manpower costs.
  • Access: Many commercial buildings have A/C units, solar panels and satellite dishes installed on the roof, and having a flat roof offers easy access to service that equipment.
  • Height: Many communities in Southwest Florida have height restrictions on new construction, so a three-story building with a flat roof, for instance, can squeeze under a 35-foot height restriction. With a sloped roof, developers might be limited to just a two-story facility.

Flat or low-slope roofs also have drawbacks, some of which include:

  • Ponding water: If a flat roof is properly designed, water can still drain properly. Unfortunately, many older buildings might have developed lower spots or divets over the years. Standing water is the enemy because it can break down roofing materials, become a breeding ground for mosquitoes and pests, expedite mold growth and lead to roof failure.
  • Weight: Pooled water can significantly increase pressure on a roof structure. One gallon of water weighs more than eight pounds, so large puddles add extra pressure to a roof that wasn’t factored into the design. Thankfully, we don’t have to worry about snow and ice buildup on roofs in Florida.
  • Leaks: Water naturally travels downhill, and if a flat roof has any cracks or buckles in the membrane, water will travel right into a building. Over time, flashing can become loose or degraded, which also is conducive to leaks.
  • Life expectancy: While metal panels can have a life expectancy exceeding 50 years, flat roofs typically last one-third to one-half of that time. Regular maintenance and inspections are crucial for property owners looking to maximize the life expectancy of their roofs. The roofs we install each come with materials and installation warranties, and we also suggest a preventative maintenance plan to keep a roof in tip-top share for years to come.

Questions about your flat roof? Call Target Roofing today at 239-332-5707 or email us at


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