Most commercial buildings have a flat or low-slope roof. These roofs pose a unique set of challenges that you don’t find when working with residential roofs, where the slopes are steeper. Commercial roofs often collect not only water, but grease and chemicals from HVAC equipment. There are specialized materials developed for commercial roofs that provide protection during extreme weather conditions, durability, and, in some cases, aesthetic appeal.
Whether you’re looking to replace your current commercial roof or are constructing a new building and want to know what your options are, we’ve got a list of eight popular commercial roof types and their pros and cons to help you decide which is best for your building.
Membrane roofing systems
Membrane roofing systems are made up of compounded synthetic materials in the form of flexible sheets and are among the most popular roofing materials for commercial roofs. They require only one layer to provide complete protection, whereas asphalt systems often require four or five layers. They’re used on a variety of commercial buildings and offer strength, durability, and flexibility.
Membrane roofs can be mechanically attached to the roof deck using fasteners, attached using adhesive, or ballasted utilizing loose rocks to hold the material in place. Membrane seams are joined using heat or solvents, providing excellent protection against leaks.
The three main membrane roofing types are TPO, PVC, and EPDM.
TPO
Thermoplastic polyolefin (TPO) is made from synthetic rubber and a reinforcing scrim, and it has a lifespan of 10-25 years. It’s only used on flat roofs and is highly resistant to fats and oils that may accumulate there, especially from restaurant equipment. It’s generally white in color and reflects sunlight, keeping the building cooler and reducing the energy needed for air conditioning.
Pros
- Reflective color reduces the need for interior cooling
- Fire resistant
- Wind resistant
- Resistant to chemicals
- Cost-effective
Cons
- Can be damaged or punctured
PVC
Polyvinyl chloride (PVC) roofs often look like TPO and have an expected life of 15-30 years. They’re also resistant to chemicals and grease/oil, and provide excellent durability during weather extremes. A white PVC roof also reduces cooling costs by reflecting sunlight. The seams are hot air-welded, providing maximum strength and leak prevention.
Pros
- Resistant to chemicals, high winds, and extreme weather
- Fire resistant
- Improves energy efficiency
Cons
- Can be damaged or punctured
EPDM
EPDM stands for ethylene propylene diene monomer and is a rubber polymer used to create a roofing membrane that can last 20 years or more. It can be attached to the roof deck with adhesives, fasteners, or ballast such as rock. It’s cost-effective, long-lasting, fully recyclable, and works best on flat and low-slope roofs.
Pros
- Durability against sunlight and chemicals
- Long life span (up to 50 years with proper maintenance)
- Increases energy efficiency
- Fire resistant
- Withstands cold, acid, alcohol, and solvents
- Quick to install and repair
- Low maintenance
- Cost-effective
- Made from recycled materials and fully recyclable
Cons
- Not aesthetically pleasing
- Must be installed correctly to avoid seam leaks
- Requires training and experience to install correctly
Asphalt roofing systems
Asphalt, or bitumen as it is sometimes referred to as, is a liquid or semi-solid form of petroleum that can be used for roads or roofing. When paired with materials like fiberglass or felt, it creates a durable, waterproof protective barrier that requires little maintenance.
Asphalt roofing materials include BUR, modified bitumen, and asphalt shingles.
Built-up roofing (BUR)
Built-up roofing systems consist of alternating layers of bitumen (asphalt) and roofing felt or fabric. Each layer of a BUR roof is called a ply, so “three plies” refers to three layers. A top layer of loose rock or gravel weighs down the system.
Because a BUR roof has multiple layers of protection, it can withstand building stress, temperature changes, and punctures.
Pros
- Durability
- Longevity (20-50 years)
- Fire resistance
- Waterproof
- Low maintenance
- UV resistant
Cons
- Labor-intensive installation
- Difficult repairs
- Susceptible to damage in cold temperatures
Modified bitumen
Modified bitumen or torch-down roofing is made from asphalt modified with rubber or plastic to increase flexibility and enhance the strength and stability of the reinforcing material (roofing felt). There are two primary modifiers: APP (atactic polypropylene) and SBS (styrene-butadiene-styrene). The system is reinforced with fiberglass and polyester mats and scrims, an open-mesh material.
Mod bit membranes are usually installed as a two- or three-ply system, with the reinforcing material mopped down with hot asphalt and the seams heat-welded using large flame-throwing torches. The membrane is attached to the roof deck with an adhesive, mechanical attachment (fasteners), or by the use of ballast, such as loose rock or gravel. It’s usually used on low-slope or flat roofs.
Pros
- Quick installation
- Low maintenance
- Cost-effective
- Performs well in extreme temperatures and wind
- Durability (from multiple layers)
- UV protection
Cons
- Short lifespan (15-20 years)
- Odor during installation and after
- Fire danger from the blowtorch used for installation
- Can be expensive
- Not suitable for areas with high rainfall or snow
Asphalt shingles
While asphalt shingles are extremely popular for residential roofs, commercial buildings often need a more durable, stronger roofing system to withstand damage from foot traffic and debris. Commercial buildings with asphalt shingles usually use dimensional or architectural shingles, which are more durable and offer a nice 3D effect.
These asphalt shingles offer better wind protection and a 3D aesthetic that resembles shakes. They’re made up of multiple layers of asphalt-coated fiberglass mats and are used on low- and high-slope roofs. Ceramic granules on the top of the shingles reflect sunlight, providing UV protection.
Pros
- Affordability
- Aesthetically pleasing (available in multiple colors)
Cons
- Short lifespan (25-35 years)
Other systems
While most commercial roofs are covered with one of the roofing systems discussed above, there are two other alternatives: metal and green roofs.
Metal
The most common metal for roofs is corrugated galvanized steel. Others include copper, aluminum, stainless steel, and tin. Metal roofing can be used on commercial, institutional, and industrial buildings.
The most popular form of metal roof is standing seam roofing. The term refers to the interlocking seams that run vertically between panels. A seaming tool is rolled along each connection point, crimping the seams together and ensuring a watertight seal.
Metal roofing comes in a variety of colors (with a 20-45-year warranty on the finish), so it can add aesthetic appeal as well as protection. Metal roofing should be used only on low- and steep-slope roofs to ensure proper drainage.
Pros
- Lightweight
- Fire resistant
- Longevity (50+ years, copper/zinc up to 100 years)
- Heat resistant
- Impact resistant
- Low maintenance
- Improve building energy efficiency
Cons
- Significant cost
- Can be noisy during rain or hailstorms
- Possible denting from debris
Green
A vegetative or green roof is made up of living plants installed in tray systems atop a waterproof membrane. They provide excellent stormwater control and aesthetic appeal, as they resemble garden spaces.
Due to the weight of a green roof system, the building’s structural framework must be designed with the system in mind. If you’re considering adding a green roof to an existing structure, make sure a structural engineer reviews the design to confirm it can support the weight.
Pros
- Cleans pollution from the air
- Improved insulation
- Reduced stormwater runoff
- Long life expectancy (50-75 years)
Cons
- Heavy
- Significant cost
- High maintenance
The team at New Roofs Inc. is experienced in installing, repairing, and maintaining membrane, asphalt, and metal commercial roofing. If you have questions about which commercial roofing material is best for your building, contact our team of experts for answers.