The Structure of a Commercial Roof

When it comes to commercial roofing, you’re likely to find these basic roof structures atop a commercial facility:

  • Flat: A flat commercial roof doesn’t have a slope or peak in the roof. For this reason, the accumulation of snow and rainwater can be a chief concern for a business.

A flat roof is made up of three different layers that form the roof structure: a foundational weather-resistant layer to keep out moisture, a reinforcement layer to prevent damage, and a protective top layer to shield the two bottom layers from debris, heat, and foot traffic.

  • Low Slope: A low sloping roof on a commercial facility isn’t likely to have more than a 3:12 slope (14°), meaning a decline of 3 inches per foot. With this type of gradually sloping roof, water accumulation still remains a major concern, similar to the flat roof listed above.

For this reason, a low sloping roof will be constructed with the same three layers as a flat roof to prevent moisture collection and protect roof materials from outside damage.

  • Steep Slope: Any commercial roof with a slope greater than 3:12 (14°) is considered a steep sloping roof. With this type of roof slope, water buildup should not pose an issue.

Therefore, a steep slope roof covering can be reinforced with other attractive, protective roofing materials like concrete, clay, slate, or asphalt, just like a residential property.

Here is a helpful depiction of basic commercial roof layers used on a flat or low slope roof for reinforcement:5roof2