Whether you need a new roof for your commercial building or just started managing a new-to-you roof, you’ll want to make better decisions regarding roof replacement, repair, and maintenance. Knowing more about different flat roof covering types, their lifespan, pros and cons, and maintenance requirements can help ensure you have a lasting, sturdy cover for your investment. Let’s review the 5 most common flat roof coating types available for your commercial property.
Built-Up Roofing (BUR)
Built-Up Roofing, also called “BUR” or “tar and gravel” roof, is one of the oldest and most common commercial roof covering types. It is typically created with four basic components:
- Base sheet
- Felts or reinforcing fabrics
- Surfacing component
The layers of bitumen and reinforced fabric are applied one on top of the other at least four times, creating a finished four-ply membrane. The roof is usually surfaced with gravel, mineral surfaced cap sheets, or glass fiber to provide UV protection.
If the bitumen is made of coal tar or asphalt, it will be heated so it liquefies before being applied with mechanized spreaders or mops. If the bitumen is a cold-applied adhesive, the installation will not require the use of heat.
Depending on the specific materials used and the climate, BUR roofs have an expected lifespan of 15 to 30 years. The multiple layers of bitumen and felts create a more rigid and stable surface to provide excellent waterproofing and UV protection. They’re also low-maintenance and have high resistance against strong winds and fire.
On the downside, the installation costs of built-up roofing are relatively high. Also, BUR can be slow to install and involves hazardous fumes when heat is used. Some types of BUR can be susceptible to punctures and water damage.
When it comes to maintenance, built-up roofing requires inspection at least once a year to ensure problems don’t get out of hand. A fresh coating every 4 to 6 years is also required to protect the roof from solar damage and ensure it does not deteriorate quicker than expected.
EPDM Rubber Roof
EPDM (ethylene propylene diene terpolymer) is a synthetic rubber roofing membrane made of a mixture of sawdust, recycled tires, and slate dust. Its two primary ingredients are propylene and ethylene, which are derived from natural gas and oil. EPDM is manufactured in rolls and available in either black or white. This roofing type can be installed either:
- Fully adhered
- Mechanically attached
EPDM is one of the least expensive flat roof materials on the market today. It is lightweight, eco-friendly, durable, and highly resistant to fire, wind, and extremely low temperatures. A good quality EPDM roof can last up to 50 years or longer.
The biggest drawback to the EPDM rubber roof is its appearance. A black rubber roof doesn’t have an aesthetic appeal, especially if it can be seen by people on taller buildings. Also, EPDM can be punctured easily by foot traffic, falling objects, or rooftop equipment.
To get the most out of your rubber roof and extend its life even further, you should have it properly maintained about 3-4 times a year and right after a period of bad weather. Maintenance typically involves inspecting the roof, keeping it clean, and repairing scuffs, holes, and marks.
Thermoplastic polyolefin, or TPO for short, is one of the newest and commonly used commercial roof covering types in the industry. TPO is a single-ply membrane consisting of a combination of ethylene-propylene rubber and polypropylene. It’s also manufactured with fillers such as carbon fiber, fiberglass, and talc to add to the TPO’s flexibility and strength.
The TPO membrane is secured to the roof deck by mechanical fasteners and plates. Each sheet is installed overlapping the last and then seamed together using hot air welding.
TPO has gained considerable use with flat roofs in large part due to its natural ability to deflect UV rays. This can help extend its lifespan and lower cooling bills on those hot, sunny days. TPO is also lightweight, strong, flexible, and more resistant to punctures, tears, and damage. TPO is a “greener” choice because it doesn’t contain environmentally-harmful chemicals like chlorine.
While TPO roofing has an expected lifespan of 20 to 30 years, one of its biggest drawbacks is it’s relatively new. There’s also great variability in the quality of the materials since manufacturers are constantly changing their formulations to address the issues of seam failures and material failures. And while TPO has a natural reflective ability, it is prone to failure with excessive exposure to high temperatures.
TPO maintenance typically involves annual or biannual inspections, cleaning the roof, and having minor damage repaired when detected.
PVC is a single-ply membrane made from two layers of polyvinyl chloride with polyester added in between to increase flexibility and strength. PVC can be installed by heat welding the seams or using mechanical fasteners to attach it to the roof deck.
Through the heat welding installation, the roof covering is ensured to last a long time because the process creates a permanent bond between each roofing sheet. The result is an exceptionally strong, durable roof material. PVC roofs are specifically engineered for strength and have a breaking strength of at least 350 pounds per square inch.
PVC is watertight and highly resistant to chemicals, fire, and wind. Thanks to its cool reflective properties, this roofing material is energy-efficient, helps mitigate the heat island effect in urban areas, and offers protection against damage and discoloration from the sun’s radiation.
The biggest downside to a PVC roofing system is the higher initial cost. The material itself is expensive and the installation costs are higher because insulation boards have to be installed first.
A high quality, properly installed PVC roof can last over 20 years with minimal maintenance requirements during its service life. Correct drainage, regular inspections, and proactive maintenance are critical to preserving your PVC roof even longer.
Modified Bitumen roofing is a modern evolution of built-up roofing (BUR). The term “modified” refers to the addition of modifiers to the standard roofing asphalt or bitumen. The modifiers are usually rubber or plastic-based polymeric binders to help improve the roofing product’s durability and performance. Reinforcing fiberglass or polyester fiber matting is then added to bitumen for extra strength.
Most modified bitumen systems consist of two layers: a base sheet which self-adheres and a cap sheet with a granular surface. A modified bitumen roof can be torched down, self-adhered, or cold adhered.
The two most common types of modified bitumen roofing are SBS (Styrene-Butadiene-Styrene) and APP (Atactic Polypropylene). SBS is a rubber polymer mixed with asphalt. It increases the membrane’s flexibility and gives it stronger contraction and expansion capabilities. APP is a rubber polymer mixed with asphalt. It increases the roof system’s aging ability.
Modified bitumen is highly durable, flexible, and has high tensile strength. It’s also easy to repair and resistant to fire, hail, and wind. When it comes to the downsides, modified bitumen is more labor-intensive, heavyweight, and tends to absorb too much heat. It also breaks down when subjected to grease, fats, and chemicals, like those found on factory or restaurant roofs.
With proper installation and maintenance, a modified bitumen roof can easily last 20 years or more.
Work with Perfection Roofing
The contractors at Perfection Roofing have extensive experience installing, replacing, and maintaining flat roofing systems with efficiency and speed. We use high-quality materials and work to ensure complete satisfaction that your flat roof will be in good condition for many years to come.
If you have any questions or concerns about your Birmingham area flat roof, contact us today to learn more.