High Construction Company--How to Choose a Roofing System

The roof you choose for your new building should serve as a first line of defense against sun, wind, rain, snow, foot traffic, grease, and chemicals, all of which can threaten your facility’s condition and longevity.

Which roof you choose and how you apply it depends primarily on your project’s location and climate and on your building’s use and design, explains Matt Knouse, a manufacturer’s representative for Performance Roofing Associates, Exton, PA. The roof that works best for a casino on the Jersey shore, for instance, will be different from the system most suited to a distribution center in central Pennsylvania, he says.

Other factors that determine your roof choice are accessibility of materials and labor in your area and the locale’s insurance requirements and regulations. But regardless of your specific circumstances, if you make the effort to choose a roof system and maintenance program well suited to your situation, it can offer reliable protection for your building and its contents for many years.

Types of Roofing Systems
Frank Fox, AIA, president of Greenfield Architects, Ltd., Lancaster, PA, says that “in general the industry uses very low-sloped roofs in commercial building,” although there are exceptions, such as for churches or residential-looking hotels, in areas with high snowfall amounts or when an aesthetic accent is needed.

Low-slope roofing systems more easily cover the long-beam spans typically used in commercial construction, explains Gary Stroud, property services manager for High Associates, Ltd., Lancaster, PA. The most common of these are single-ply membranes, including thermosets, such as ethylene propylene diene monomer (EPDM) and thermoplastics made of either thermoplastic polyolefin (TPO) or polyvinyl chloride (PVC).

EPDM Rubber
The best known of the thermoset systems, EPDM is commonly chosen for distribution centers and office buildings but can be applied for other uses as well. “EPDM’s main advantage is its 300 percent elongation rate, which allows it to expand and contract with temperature changes, be easily shaped around special roof equipment, and fit over any roof design, says Knouse.

Manufactured in 100-foot long rolls, EPDM covers a large area quickly, making it easy to install and less costly than other roofing systems.

Workers install a fully adhered EPDM roof system placed above ¼” DensDeck® recovery board. The recovery board was mechanically attached using screw-type fasteners and plates. The seams on the EPDM roof were completed using a contact seam tape. The new roof system was installed above an existing smooth surface built-up roof, after removing any wet roofing and insulation identified by an infra-red scan. (Photo courtesy of Houck Specialty Contractors)

EDPM’s naturally dark color often makes it an ideal choice north of the Mason-Dixon line. “In the dead of winter, a black roof will probably help you somewhat with heating costs,” says Vice President John Dorfler, Houck Specialty Contractors, Harrisburg, PA. You can increase an EPDM roof’s reflectivity—an advantage in southern climates—by applying a light-colored hyplon or acrylic coating. But every few years, you have to recoat it.

On the downside, rubber breaks down more quickly than other roofing materials if chemicals or animal fats come through exhaust systems onto the roof or if the building requires a lot of foot traffic to service roof equipment. Seam laps were a problem in the past, but today adhesive seam tapes take most of the guesswork out of sealing EPDM seams, says Dorfler.

Dorfler estimates initial costs at $2.75 to $5 per square foot for EPDM roofing, depending on the type of insulation used.

Thermoplastics
PVC and TPO are the most common thermoplastics, which are single-ply systems best known for their ability to change from a solid to semi-solid state when heated. This property allows separate overlapping panels to be fused together to create one continuous membrane when cooled. Heat reflectivity makes these roofs a good choice in warm climates, where they can help reduce cooling costs.

According to Knouse, “You still see PVC used on fast food restaurants where there is a high animal-fat content,” which doesn’t break down PVC as quickly as it does other systems. But overall, the disadvantages of PVC have tipped the market in TPO’s favor, say Knouse and Dorfler. TPO mimics PVC’s advantages without some of its disadvantages. For example, says Fox, “With PVC it’s recommended to spend extra to increase membrane thickness and reinforce it with fiberglass to help limit plasticizer migration, which can cause brittleness and cracking over time.” And, says Dorfler, PVC contains chloride, which emits harmful fumes when heated.

Manufactured in a variety of colors, TPO is also a good choice when aesthetics are an issue, such as in a hotel, Dorfler adds. It’s also more resistant to certain chemicals, fats and oils than EPDM,” says Dorfler. And, says Fox, while not as flexible as EPDM, TPO is more pliable than a multi-layer asphalt system and therefore “easier to work with when installing flashing around a lot of penetrations and equipment.”

Dorfler warns, however, that TPO’s advantages, especially reflectivity, are contingent on regular cleaning, which can be a major maintenance item. Initial costs for TPO are similar or “slightly higher than for an EPDM roof,” says Dorfler. “But if you factor in maintenance, the life-cycle costs of TPO will be higher.”

The Built-Up Roof (BUR)
Because of costly labor to install built-up roofing systems, they are less common than single-ply membranes in new commercial construction. These multi-layer systems of asphalt and felt, however, work particularly well in situations where extra protection is needed. For example, says Dorfler, if a roof will sustain a lot of foot traffic or be subject to excessive debris over its lifetime, like the roofs of some paper plants and food manufacturers, the multi-layers will withstand the wear and tear far better than a single-ply system. For an added benefit, covering the roof with light-colored gravel can increase reflectivity, he adds, although it’s not as good as with TPO.

The newer, modified asphalt is more flexible than traditional asphalt, but BURs do not provide the pliability of EPDM or TPO. Installation also requires higher insurance costs due to application methods that use heat and open flames or spray. A simple BUR might cost $3.50 to $4 per square foot, estimates Dorfler, but a complex project could run as high as $7 to 10 per square foot, depending on the insulation and amount of roofing equipment and special features installed.

What’s in a Warranty?
“Today’s warranties cover both labor and material,” typically for 10 to 15 years, says Dorfler, who adds that additional costs for a 20- or 30-year warranty may not be justifiable. Stroud recommends buying both an applicator’s warranty and a material warranty for 10 years each.

According to Dorfler, “The cost of warranties—depending on the type of roof system, wind-speed coverage, and duration—can range from four cents to 20 cents per square foot. Normally, all costs associated with warrantable repairs will be borne by the manufacturer.

Dorfler suggests that owners “purchase a 15-year warranty for about seven cents per square foot and escrow the difference between a 15- and 20-year warranty and use those funds toward annual maintenance. This is crucial because without a good maintenance program, a warranty may not be valid.” Although covered repairs will be honored throughout the life of the warranty, the building owner is responsible for maintenance. “It’s similar to buying a new car with a 100,000-mile warranty,” Dorfler adds. “You can’t ignore regular maintenance like oil changes, and then expect the manufacturer to fix the resulting engine damage.”