Flat, low slope, or low-pitch roofs all refer to roofing systems with a pitch of less than 10 degrees. Widely used for commercial buildings, flat roof homes were historically popular in hot, dry climates. Modern materials and innovative architecture have optimized flat roofing systems for many climates.
Asphalt / Modified Bitumen
Asphalt -- or bitumen -- is a durable, petroleum-derived material. Its durability and versatility make it an attractive roofing option for flat roof homeowners. Asphalt for flat roofing is typically applied in roofing rolls; the material itself can either be SBS (styrene-butadiene-strene) or APP (A-Tactical Polypropylene). These membranes handle well in hot climates or regions with temperature swings; asphalt handles thermal movement very well, meaning the material remains resilient as it expands (with heat) or contracts (with cold).
Modified Bitumen is when asphalt is reinforced with additional materials -- like fiberglass, rubber, or other thermoplastics. These modifications combine the flexibility of asphalt with the waterproof properties of the added materials, resulting in a durable (yet flexible) roofing system that adapts to a wide range of climates.
EPDM stands for Ethylene Propylene Diene Monomer. It is a synthetic rubber, and is a very common roofing membrane material. EPDM offers excellent waterproofing, and is a low-maintenance solution for flat roof houses. EPDM roofs handle heat well, and don’t break down or degrade in high temperatures. EPDM membranes can be installed in several ways, including ballasted, fully adhered, or mechanically attached.
PVC -- or Polyvinyl Chloride -- is another membrane roof material for flat roofs. The flexibility and weather-resistance make it an excellent option for flat roof homes in windy, high-temperature, or storm-prone regions. PVC roofing is susceptible to cracking in cold weather.
TPO is a very versatile membrane for flat roof homes, and is widely used on commercial buildings due to its UV-resistance and simple installation. TPO is more affordable than PVC, but does require more frequent replacement. It is typically mechanically attached.
Flat roofs differ from sloped roofs in their maintenance. If your house has a flat roof, it’s important to schedule regular inspections to prevent excessive ponding. Ponding is when standing water accumulates, forming puddles on a flat roof surface. Regular inspections with an experienced contractor will ensure your flat roof is draining properly and that seams aren’t leaking or cracking.
Keep your flat roof clean by removing debris (like leaves and branches); unlike steep-slope roofs, flat roofs are prone to collecting piles of seasonal debris. Finally, call your contractor if you notice any punctures or tears to your roof’s membrane; small holes can be repaired, but can cause major damage to your home if not treated quickly!