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  • Mark Forbes

Why are Commercial Roofs Flat?

In comparing residential and commercial roofs, one noticeable difference stands out, the size and pitch of each can vary greatly. Commercial roofs generally look flat, but in actuality, no roof is ever perfectly flat. It is more accurate to refer to flat roofs as “low-slope”; a roof must have a gradual slope for drainage. There are a variety of reasons why commercial roofs are engineered to be low-slope.


Low-slope Commercial Roofs

Low-slope commercial roofs are cost-effective for large buildings. Businesses can easily store mechanical units, such as A/C on large flat roofs which makes for easy access and maintenance. Pitched roofs often used on residential buildings would not be cost-effective on large retail or industrial buildings.

Benefits of Flat Roofs

Both commercial and residential buildings can reap the benefits of a low-slope, flat roof. Here are five benefits of installing a flat roof.

  1. Easy to inspect

  2. Mechanical system friendly (HVAC, Solar)

  3. Easy to maintain

  4. Affordable to install

  5. Pleasing design for modern residential architecture

Residential Pitched Roofs vs. Modern Flat Roofs

Residential homes often use pitched roofs which can offer aesthetic qualities to homes and neighborhoods. However, modern residential home architecture is bringing back the flat roof design for many of the same reasons that commercial buildings use flat roofs; ease of maintenance, cost-effectiveness, and the potential for additional space.

Commercial Roofing Materials

When working with flat, commercial roofs, selecting the right roofing material is paramount for the longevity and effectiveness of your roof. United Materials works with every customer to identify the perfect roofing materials for their project. Below are a few of the common commercial roofing materials that we use at United Materials.


  • TPO (thermoplastic polyolefin) roofing. A single-ply roofing membrane. Excellent performance at a cost-effective price.

  • PVC (polyvinyl chloride) roofing. Reliable and versatile. Offers excellent flexibility and resistance to UV, chemicals, ozone, punctures, and tears.

  • Liquid membranes. Liquid material that is flexible, highly reflective, and easy to repair. Excellent protection from the elements.

  • Modified bitumen APP and SPS. Made from asphalt modified with polymers or solvents. Offers flexibility, impact resistance, and excellent strength.

  • Built-up roofing (BUR). Excellent for demanding applications. Continuous, semi-flexible roof membrane made of layers of saturated and coated felts, fabrics, or mats, with alternate layers of bitumen.

  • EPDM (ethylene propylene diene monomer) roofing. Lower cost, highly elastic, durable, and UV resistant. A popular commercial roofing material.

  • Metal roofing. Durable and popular with a 40 to 60-year service life.

At United Materials we install, service, and repair all types of commercial roofing; from churches and retail buildings to schools and government facilities, we bring 100 years of expertise to every project. Give us a call, we look forward to discussing your roofing needs.



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