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NATIONS ROOF® BLOG​

Roofing for Commercial Spaces: Flat Systems vs. Sloped Systems

view of metal roof - flat vs sloped commercial roofing systems

Roofing systems for commercial spaces often come in two primary types: flat vs sloped commercial roofing systems. Before continuing this discussion, it’s crucial that you realize that despite being called “flat,” a flat roof has a slight slope for drainage purposes. A flat roofing system is called that because the slope is not very noticeable. With that said, flat and sloped roofs have pros and cons. Here are some to consider.

Flat vs Sloped Commercial Roofing Systems

  • Flat roofing systems offer cost-effective installation, additional usable space for rooftop installations, easy maintenance access, and modern aesthetics, but may face drainage challenges and limited insulation. 
  • Sloped roofing systems provide adequate water drainage, enhanced insulation capabilities, aesthetic variety, and durability in harsh weather but come with higher installation costs and limited usable space on the roof. 
  • The choice between flat and sloped systems depends on factors such as budget, space utilization needs, aesthetic preferences, and climate considerations.

Do you find yourself having to select a commercial building? Here are things to consider when deciding on a flat vs. sloped commercial roof. 

Flat roof systems

Also called low-slope roofs, “flat” commercial roofs may have a slope less than 1:12. They are designed to be nearly horizontal, allowing for easy installation of roofing materials such as single-ply membranes, built-up roofing (BUR), or modified bitumen. Here are the pros and cons of commercial flat roofing systems. 

Pros of flat roofs

Cost-effective installation: Flat roofs are generally easier and quicker to install than sloped roofs, which can lead to cost savings on labor and materials.

Space utilization: A flat roof system can provide additional usable space for rooftop installations such as HVAC units, solar panels, or recreational rooftop space.

Easy maintenance: Flat roofs are easier to access for routine maintenance and inspections, making it simpler to detect and address issues like leaks or damage.

Modern aesthetics: Flat roof designs can contribute to a modern and sleek aesthetic, especially for contemporary commercial buildings.

Cons of flat roofs

Drainage challenges: Flat roofing materials require proper drainage systems to prevent water pooling, which can lead to leaks and structural issues if not managed effectively.

view of flat roofing system

Limited insulation: Flat roofs may have limited space for insulation compared to sloped roofs, which can impact energy efficiency and heating/cooling costs.

Durability concerns: A low slope roof or flat roof may be more susceptible to damage from weather elements like heavy rain, snow, or debris accumulation, requiring regular maintenance.

Sloped roof systems

Commercial sloped roofs have a noticeable pitch or slope, with angles that vary depending on the architectural design. Standard slope ranges for sloped roofs are 2:12 (2 inches rise per 12 inches of run) to 12:12 or steeper. Sloped roofs often use commercial roofing materials such as asphalt shingles, metal roofs, clay tiles, or concrete tiles.

Pros of sloped or pitched roofs

  • Effective drainage: A sloped commercial roof system naturally facilitates water drainage, reducing the risk of water pooling and associated issues like leaks or structural damage.
  • Enhanced insulation: Sloped roofs allow for thicker insulation layers, improving energy efficiency and providing better thermal performance for the commercial property.
  • Aesthetic variety: Sloped roofs offer a wide range of design options, including traditional styles like gable, hip, or mansard roofs, which can enhance the building’s traditional aesthetic appeal.
  • Durable in harsh weather: Sloped roofs are generally resilient to harsh weather conditions such as heavy rain, snow, or high winds, reducing the need for frequent repairs.

Cons of sloped or pitched roofs

  • Higher installation costs: Sloped roofs typically require more labor and materials, leading to higher upfront costs than flat roofs.
  • Limited usable space: A pitched roof may limit the usable space for rooftop installations or activities, which can be a consideration for certain commercial properties.
  • Complex maintenance: Some sloped roof designs may be more challenging to access and maintain, especially for areas with steep slopes or intricate roof structures.

Ultimately, the choice between flat and sloped roofing systems for commercial spaces depends on factors such as budget, building design, climate considerations, maintenance preferences, and aesthetic priorities. Consulting with Nations Roof and considering long-term performance and cost-effectiveness can help make an informed decision. For expert advice on all types of roofing materials and systems, contact Nations Roof. We are roofing industry experts and will be happy to complete an inspection and analysis of your commercial buildings. 

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