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Inspecting Modern Flat / Low Slope Roof Coverings

When I first started conducting home inspections many of the flat or low slope roofs were covered with roll asphalt for residential applications or built up roofing for commercial. Although some people may still use roll roofing, and it may have its place; most modern flat roof coverings are made from newer, more durable, and more waterproof materials. Some of the materials that are commonly used for flat roofs are IRMA – Inverted Roof Membrane Assembly which is widely used for commercial applications. Normally you would not see this on a residence. IMRA incorporate insulation in the assembly and have a protective coating that may contain gravel. Modified / Polymer Bitumen which can be Atactic Polypropylene or Styrene Butadiene Styrene is a rubber like compound that is installed in sheets. Elastomeric or EPDM are sometimes called rubber roofing. PVC or plastic roofing materials are also available. These types of materials are most common for modern flat roofs. Some bitumen coverings may be prone to damage from the sun’s rays unless they are coated with ultraviolet protection. Bitumen materials can also be reinforced with fiberglass. Flat roof covering materials can be applied by heating (torch down), peel and stick, or glued down. It will be difficult for a home inspector to identify the different types and specific materials of bitumen. We normally refer to these types of coverings in our reports as a “Single Ply Membrane.” Here are some of the things home inspectors should be looking for when inspecting single ply membranes on flat roofs:

  • Seams facing the wrong direction which could cause water entry
  • Cracking or splits in the membrane
  • Blisters / wrinkling
  • Any areas that have been repaired or patched
  • Seams that are not overlapped at least 3 inches
  • Areas that have “bubbled” or are not properly attached to the substrate
  • Ponding / standing water
  • Any puncture or tear in the material
  • Side & end laps should be staggered
  • Flash points especially around air conditioning systems due to vibration
  • Flashing around parapets
  • Flashing around skylights
  • Flashing around any roof drains
  • Examine any drains that travel through the interior from underneath if possible
  • Ensure the water is draining properly including the drainage system / gutters

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