Residential Flat Roof - Classic Roof Replacement

3 Types of Residential Flat Roofing

All structures need a roof to keep the elements at bay. For many decades industrial buildings were topped off with flat roofs. It remains one of the most cost-effective solutions for large surface areas. This is why it is so common for commercial or industrial structures. But what about residential roofing? Would residential flat roofing work for your house? 

Flat roofs can offer advantages for homes, including a modern or minimalist design, increased energy efficiency and more living space for its occupants. 

Unlike a steeply pitched roof, most of the square footage under a flat roof can be livable space. A flat roof can host patios for entertaining or exercising, rooftop gardens or out-of-sight solar panel installations. Any of these applications will require certain design considerations, such as adding railings or other safety features. Special permits may be required for a flat roof from the local building authority as well. 

Residential Flat Roofing Basics

The three major types of residential flat roofing are:

  • Built-up roofing, aka BUR
  • Modified bitumen roofing
  • Single-ply membrane

The team at Classic, all of whom have been certified by the GAF Roofing Academy, has installed all three of these flat roof systems countless times. Keep in mind that flat roofs are not completely flat. They do have a slope to them, usually from single digits to up to 15 degrees, to allow water to flow into drainage or gutter systems. 

Let’s learn more about each of these types of residential flat roofing systems, as well as some of the advantages and disadvantages.

Built-Up Roofing or BUR

The built-up roof system, often referred to by the acronym BUR, is the OG (original gangster) of flat roofing systems. It’s been in use for more than 100 years in the United States.  

However, it’s unlikely to find BUR on any homes in recent years. That’s because of the advent of other roofing materials that are more suitable for residential properties with flat roofs. But BUR is still the popular style of commercial or industrial structures. 

While BUR can be built in a variety of ways, generally, it’s a roof made up of roofing felt or ply sheets covered with a layer of hot asphalt. This consists of melting bricks of asphalt in metal kettles and using mops to apply asphalt in between a base sheet, a ply sheet(s) and lastly a cap sheet. The more layers, the more durable and long-lasting the roof will be. The layers are topped off by a cap sheet or a coat of asphalt and granules or spreading gravel and slag.

The popularity of this roofing system was due to the affordability of multiple layers, helping building owners shield their property from the elements for long durations at a cost-effective price point.  

Today there are also cold-applied adhesive solutions that take out the smell and some of the difficulty of BUR.

Where BUR is Used

BUR is often used on essential buildings, such as schools, hospitals and key infrastructure buildings, that need to stay open and operational at all times.

Modified Bitumen Roofing or MBR

This roofing system still uses asphalt, it’s just the asphalt is modified slightly. A polymer or synthetic rubber or plastic is mixed into the asphalt or bitumen and reinforced with fiberglass or polyester during the manufacturing process. Here are some of the MBR products produced by GAF that Classic Roofing & Construction has applied to homes and commercial structures.

SBS Roofing

SBS, or styrene butadiene styrene, is a synthetic rubber that allows SBS sheets to achieve greater elongation ratings than other asphalt systems. SBS systems also have the widest range of application methods. The sheets can be hot-mopped, cold-applied, heat-welded with a torch or self-adhered to the roof decking. A typical SBS system consists of two plies of roofing membrane. First, a ply of smooth-surfaced SBS base sheet is installed, typically over insulation or a cover board on the roof deck. Then the application is finished with a granulated cap sheet, which is applied over the smooth base SBS sheet. SBS membranes are classified by ASTM numbers, types and grades. The ASTM number, types and grades are specified by the architect, designer, general contractor or owner, or all professions working in concert. 

Where SBS is Used

SBS is often used on roofs requiring the reliability of asphalt with more flexible application methods and labor availability. If applied with a torch, however, a CERTA (certified roofing torch applicator) certification is required for crew members. Many areas also restrict the use of torches on roofs due to their risk as a potential fire hazard. SBS can also be applied via hot-mopping, cold-application or as self-adhered. Cold-applied applications are gaining in popularity because they don’t produce as much odor as hot-mopped, nor do they require professional certifications as with torching. Self-adhered SBS is also popular because there is no odor and it is typically faster to install.

APP Roofing

APP (atactic polypropylene) is a plastic that is added to the asphalt during manufacturing that allows the roofing membrane to achieve durability from the damaging effects of UV rays and other weather challenges. APP is applied to the roof deck using a torch — a key difference from SBS. Just like with SBS, APP systems consist of two membranes, a smooth sheet and a granule-embedded cap sheet. APP sheets are installed with a BUR base sheet or thermal barriers. This is because many substrates cannot withstand the torching application. APP sheets are also applied to existing roofing systems in areas where it is permitted by building codes. As with SBS, APP membranes are classified by ASTM numbers, types and grades, specified by the designer or contractor on the project.  

Where APP is Used

APP is often used on roofs that need the reliability of an asphalt system without the odor and labor required for hot-mopping. APP is also used on smaller commercial roofing projects, especially in urban areas. Installed with torches, there is no need for kettle buckets, or a larger labor force on site, nor the odor that comes with hot-mopping. This allows for more comfortable conditions for both roofers and building occupants. But the torch wielder needs to be certified. 

Single-Ply Membrane Roofing or TPO

Short for thermoplastic polyolefin, TPO is a single-ply membrane that offers excellent performance at a cost-effective price. TPO roofing systems are a single layers of synthetics and reinforcing scrim used to cover flat roofs.

Heat-welded seams provide superior strength for Southwest Florida’s challenging weather events. This roofing system’s long-term heat, ultra violet light, and fungal resistance makes TPO a reliable low-slope roofing system. This system does not need the plasticizers, typically a synthetic resin added to the membrane to promote flexibility, and reduce brittleness.

In the 20 years TPO has been installed on flat-roof buildings, this system has become one of the most popular building materials for low-slope roofing. More than 1 billion square feet are installed annually worldwide, making up more 50% of single-ply roofs being installed today. The rapid rise in popularity is associated with its inherent benefits, including:

  • Great value: Excellent performance against Mother Nature’s wrath at a cost-effective price.
  • Excellent seam strength: Heat-welded seams provide great seam strength to taped and other seamed roofing materials.
  • Energy-saving: Highly reflective and emissive white surface can help reduce energy costs, and urban hear island effect, making an eco-friendly choice. 
  • Inherently flexible: No need for the application of plasticizers.
  • Long-term weathering: Excellent long-term ultraviolet light, and heat resistance.
  • Naturally fungal resistant: Doesn’t require the application of biocides.
  • Versatile application methods: Including high-performance roofs requiring high wind uplift, increased puncture resistance, or quick applications.
  • Fast installation
  • Low cost
  • Weather-resistant

Proven Performance

A recent study of GAF EverGuard TPO roofs installed between 8 and 16 years ago found they all performed above ASTM standards for a newly manufactured TPO. GAF analyzed membrane samples from across the U.S. and studied thickness over scrim, surface cracking and the ability to repair aging TPO membranes. The results indicate most installations are still meeting the current ASTM D6878-19 requirements for new membranes. 

Where Installed

Installed on a variety of commercial buildings, including schools, hospitals, and manufacturing facilities.

EnergyCap Roofing

Although not a roofing sealant system technology such as BUR, SBS or APP, EnergyCap roofing membranes are factory coated with a white material that reflects sunlight away from the roof of a structure. This material enables the structures to meet or exceed ENERGY STAR requirements and LEED guidelines.

Need Another Option for Residential Flat Roofing

If none of the above are a perfect fit for your home or commercial structure, then you may be interested in spray polyurethane foam or SPF. SPF roofs are a liquid-applied solution for roofs that can seal every crack and corner. The team at Classic can apply this spray on top of nearly any roofing material, including metal, roof decks, substrates or even asphalt shingles. The result is a roof system that is durable, long-lasting and energy efficient.

If you need help deciding on what approach is best for your project, reach out to the team at Classic Roofing & Construction. We are an award-winning roofing company specializing in residential and commercial roofing in Southwest Florida, including St. Petersburg, Clearwater, Tampa, Fort Myers and surrounding communities. Call us at 727-732-3495 in Tampa or 239-932-5225 in Fort Myers, or schedule a free estimate.

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