How does Commercial Roofing Differ From Residential Roofing?

Commercial Roofing System in Florida

When considering a roof replacement on a commercial building, you may wonder why its roof seems different from the roof on your home. Commercial roofing systems differ from residential roofing depending on the pitch of the roof and the main use of the building. An experienced roofing contractor knows the many different types of commercial roofing systems and which one to use for specific commercial purposes.

Most condo associations and some storefronts will have regular asphalt shingle roofs, which is standard for pitched roofs of at least 4:12. This term means that a 4:12 pitch roof rises 4 inches for every 12 inches of horizontal distance. Most roofing manufacturers of asphalt shingles recommend a pitch of 4:12 or more. On roofs between 2:12 and 4:12, manufacturer and industry guidelines require, or at the very least recommend, special underlayment or other materials underneath shingles. Low slope roofs between 2:12 and flat cannot be shingled, and so other types of commercial roofing materials must be used.  

Asphalt shingles on a commercial roofing system are installed and maintained the same as on residential roofs. For condos and similar pitched commercial roofs, roofing contractors have to assess the span of the roof and calculate the numbers for the roofing system differently. For example, a 9-foot width ice and water shield should be installed instead of the 6-foot width because there is a greater likelihood of ice building up on these larger roofs than on a single-family home roof. Ventilation numbers should be calculated differently as well. For most condo complexes, there is usually enough intake at the bottom soffit, but a smaller section of ridge vent should be used, because larger roofs have significantly more draft.

Low-slope and flat commercial roofs are generally used on strip malls, big box stores and restaurants. Unlike most residential roofs, building codes require the commercial roofing system on flat roofs to include a 3 ½” insulation foam board. The roofing material is adhered to the foam board, which is laid over the base layer. Some of the most common types of commercial roofing materials for low-slope and flat commercial roofs include:

  • Asphalt rolled roofing is commonly used on buildings with low-slope roofs and is composed of the same materials used to make asphalt shingles. As one of the more inexpensive roofing types, asphalt rolled roofing is relatively easy to install but it’s also not energy efficient. Unfortunately, asphalt rolled roofing has a very short lifespan compared to other types of roofs, typically lasting only about 10 years. Since this type of roofing product is rolled out and then adhered at the seams, leaking and other problems commonly develop where the rolls join together, increasing the need for maintenance and repairs.
  • EPDM (Ethylene Propylene Diene Monomer) roofing, commonly known as rubber roofing, is one of the most inexpensive roofing materials available. Relatively easy to install and very lightweight, a high-quality EPDM roof is not easily damaged by UV rays and can have a life expectancy of up to 20 years. Unfortunately, because an EPDM roof is black, it absorbs much of the sunlight and exterior heat, which can stress a building’s air conditioning system. Although they do not scratch or scuff easily, EPDM roofs are prone to puncturing, which means that a hailstorm or falling branch can tear a hole in your roof. Additionally, it’s important to note that adhesives are used to bond the seams of an EPDM roof. When an EPDM roof isn’t fully adhered or becomes unglued, water can travel underneath the membrane. This makes detecting the point of a leak more difficult and also allows a leak to do far more damage to the underlying structure before it can be detected.
  • TPO (Thermoplastic Polyolefin) roofing is one of the more inexpensive types of commercial roofing material and is sometimes less costly than EPDM. Installation of TPO involves a heat weld system, where the plastics in the membrane are literally melted together. This creates a more dependable bond between seams, and essentially a single sheet roof system. Because TPO is white and reflects the sun, it helps reduce heat buildup inside your building, and lessens the strain on your AC system. Like EPDM, TPO is lightweight, resistant to corrosion and breakdown, isn’t prone to algae growth or mildew, and also doesn’t need to be pressure washed. One of the drawbacks of TPO is it varies in quality and thickness, depending on the manufacturer. The top layer of TPO roofing material is laminated, making it susceptible to shrinking, cracking, crazing and deterioration. TPO rolls also typically come in narrow widths, resulting in lots of seams when installed, which could potentially weaken the roofing system and lead to future problems. Additionally, TPO itself is not fire resistant, and can be dangerous if the proper retardants are not integrated into the roofing system.
  • PVC (Polyvinyl Chloride) roofing is composed of two layers of PVC roof material with a polyester reinforcement between the layers, and includes additives that make the material UV-stable and flexible. Installation for PVC roofs uses heat welding at a lower temperature than TPO to create a permanent bond between each roofing sheet and keep the seams securely together. Like EPDM and TPO, PVC is lightweight and also very durable. The lifespan of PVC commercial roofing’s is comparatively long, as it is particularly resistant to moisture, fire, wind and chemicals. Most importantly, PVC does not absorb or become weakened by oils and greases, making it the preferred membrane for restaurants and other buildings that have grease traps on the roof. The downside of PVC: it is a more expensive option than TPO or EPDM commercial roofing. Over time PVC can shrink, which can lift the corners, pull the seams and cause leaks. In very cold weather, an older PVC roof is prone to shattering and puncturing, and PVC roofs can also be difficult to repair. In general, PVC and TPO are usually compared a lot, since they are both heat-welded and have similar characteristics. 
  • SPF (Spray Polyurethane Foam) roofing is made from a plastic that is applied to a roof deck as a liquid and transforms into a solid in seconds, while also expanding up to 30 times its original size as it dries. The SPF acts an insulative layer, and its reflective top coat helps building owners save on both AC and heating costs. A good multi-layer SPF system (such as spray foam covered with layers of premium acrylic roof coating) has outstanding tensile strength and durability. SPF can be used to correct ponding water or more effectively channel water to drains by simply spraying more spray foam in areas that need to be built up. With proper maintenance and regular roof coatings, an SPF roof can last 40 years or more. Because SPF roofing is the product of a chemical reaction between two liquid compounds, it must be applied in a carefully calibrated way or the resulting spray foam that will not last. A roofing contractor must have specialized training to apply this type of roofing material, and may need additional time to master the techniques used to apply this particular system. SPF roofing can also be difficult and expensive to remove, which may become necessary if not properly maintained.

Hear Kelly Shepard describe the different types of commercial roofing that All Weather Tite installs in Massachusetts and Florida:

For more information on commercial roofing systems and materials, contact All Weather Tite in Massachusetts, or in Florida. The experts at All Weather Tite will evaluate your commercial roof and give you the best recommendation for a commercial roofing system that fits within your budget.

Posted in Commercial Roofing, Roofing, Roofing Systems.

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