While roofing needs vary throughout the country, we've all seen houses with the ubiquitous, three-tab asphalt shingles. Slate, cedar shakes, standing seam metal, and even terracotta roof tiles round out the other typical options that homeowners have available to them. So, what is flat roofing?
What Is Flat Roofing?
Flat roofing, sometimes called rolled roofing, is a solution for homeowners with very low or flat roofs. It is used both in commercial applications as well as residential architecture with lower profiles, like mid-century modern homes. The deciding factor on when to use flat roofing instead of typical shingles or other roofing materials is based solely on the roof's pitch.
Roof pitch is the angle or slope of your roof. In other words, it tells roofing contractors how steep or flat your roof is. It is determined by dividing the height of your roof by the length. A typical roof pitch may be 4:12, which indicates that for every 12 feet, your roof changes four feet in height. Houses with a roof pitch of 3:12 or less are not considered steep enough to use typical asphalt shingles on. This is because rain and snow may not drain properly at that pitch. That's where flat roofing enters in.
Flat roofing comes in two main styles.
Built-Up Roofing: BUR, or built-up roofing, is a multi-layer fabric that is infused with bitumen and adhered directly to your roof decking. Attaching it directly to the plywood or OSB board creates an impenetrable seal so water cannot find its way into your home. Bitumen is a sticky, black tar-like substance. If you have ever been outside when a flat roof has been installed, that burnt smell you notice is the bitumen as it is being 'hot mopped' onto the roof decking. In fact, BUR is often referred to as "tar and gravel" roofing, partially due to this smell.
Modified Bitumen: BUR has been around since the 1840s, but roofing manufacturers soon realized that the product had difficulties in colder climates. The bitumen-layered fabric became brittle as temperatures dropped in the winter months. Modified bitumen was derived from efforts to find a flat roofing solution for colder climates that wouldn't suffer from the same fragility. Instead of a fabric, modified bitumen is a rubber-based product that is combined with gravel and bitumen. The rubber gives the final product some flexibility and ensures that the roof will be protected in all seasons, regardless of how low the mercury drops.
How Long Will Flat Roofing Last?
With proper installation, both built-up roofing and modified bitumen will last up to 25 years. This is slightly longer than a traditional asphalt shingle roof, which tends to last 15-20 years, and less than a metal or slate roof's amazing 50 years of effectiveness. Like any roofing material, however, the life expectancy is based on how well it was installed as well as the weather.
Precipitation, like rain, snow, ice, sleet, and hail, can take their toll on a roof. As it hits the roof over the years, it can wear away at the protective gravel that is combined into flat roofing products. Likewise, harsh environmental factors, like UV rays, high winds, and salt spray for homes on the coast, can all shorten the life expectancy of a roof. Unfortunately, there is nothing you can do to stop the weather. Plus, it is your roof's job to protect the rest of your home from the elements. You can do your best to keep sticks, leaves, and other debris off your roof and to trim back any tree branches that may be rubbing against it.
With a quality installation and proper care, a flat roof can protect your home and your family for years to come.
Contact a company like JCB Roofing for more information.