St Joseph’s Roofing….Your Flat Roofing System Specialist

Whether you have a commercial building, a small area above your front door, a rear addition, or you need to replace the entire roof, SJR can help you select the flat roofing system that is the best fit for your house or building.

We have put together an overview of the various flat roofing systems to familiarize yourself of what is available. Our experienced Project Managers are well versed and can help guide you through the selection process.


Flat roof membranes are used in both residential and commercial roofing projects. In residential, it is used predominantly for large apartment buildings, garage roofs, and small extensions. It is also increasingly used for larger main roofs in single-family housing with modern designs that integrate flat roofs.

Most large commercial projects such as apartments, warehouses, sports facilities, schools, and hotels utilize membrane roofing on flat roofs. Most of these commercial buildings require roof access for mechanical systems or they have occupied roof terraces, making membrane roofs an ideal cost effective solution.

When we say “flat roof”, we don’t mean perfectly flat, which is undesirable since water still needs to be directed to the roof drains. Technically, we are talking about low-slope roofs that have a slope less than or equal to 3:12 pitch. 

The minimum slope for a flat roof is 1/4” per foot or 1/4:12, but some owners or insurance companies require a minimum slope of 1/2” per foot. The idea is to provide positive drainage toward roof drains so there is no ponding water 48 hours after a rainstorm. The slope can be accomplished by sloping the structural deck or by using tapered insulation, or a combination of the two methods.

Always check with the roofing manufacturer to confirm the designed slope meets their warranty requirements.


EPDM Rubber Membrane
  • EPDM, short for ethylene propylene diene terpolymer, is a rubber roofing membrane that is commonly installed on residential and commercial roofs. 
  • EPDM synthetic rubber membrane is the most common single-ply membrane in both residential and commercial applications.
  • Installed as thin sheet materials 0.030 (30 mils) to 0.060 inches (60 mils) thick and are applied to the roof in a single layer.
  • EPDM rubber membrane sizes can reach 50′ wide by 200′ long. These huge pieces are great for avoiding possible leaks at the seams, but these wide rolls are also very difficult to handle during the installation.
  • EPDM rubber membrane may require a layer of insulation installed in between the roof deck and the membrane to improve energy performance. This is especially important, as EPDM membranes are commonly dark in color and will attract a significant amount of solar radiant heat.
  • EPDM membranes install like a giant sticker, but this must be done slowly and with precision to avoid air bubbles.
  • Expected Life-Span: 10-15 years

TPO Roofing Membrane:  
  • TPO, short for thermoplastic polyolefin, is a single-ply thermoplastic roofing membrane that offers good overall performance and great energy efficiency for the money.
  • Thermoplastic membranes are fabricated from polymers which soften when heated and harden when cooled. The membranes can be welded together with heat or solvents, and when welded, develop a bond strength which equals or surpasses the strength of the base material. 
  • TPO membranes are a newer product that made their initial appearance in the 1990s. TPO also comes in various color options vs the standard dark or black membranes. The default TPO color is white.
  • TPO is available in multiple thicknesses which makes them more versatile than most flat roof systems.
    • Thickness Options (in mils): 40 -100 mil.
    • 60-mil is the most commonly used residential option
  • TPO membrane chemically bonds rubber, ethylene, and propylene, as well as numerous filler materials. In that sense, it’s somewhat closer to EPDM rubber than PVC, although, unlike EPDM, TPO membrane seams are hot-air welded (not glued at the seams).
  • Similar to PVC, insulation boards are first fastened to the roof substrate. TPO also comes in rolls and can be mechanically fastened to the insulation boards or installed with the self-adhesive (fully-adhered).
  • Expected Life-Span: 10-20 years

PVC Membrane:  
  • PVC, short for Polyvinyl Chloride, is a single-ply thermoplastic roofing membrane known for its superior durability, longevity, and energy efficiency.
  • PVC membranes come in light gray and white colors.
  • The seams of PVC membrane are hot air welded, creating a permanent bond. The seams are stronger than the membrane itself.
  • Thermoplastic membranes are fabricated from polymers which soften when heated and harden when cooled. The membranes can be welded together with heat or solvents, and when welded, develop a bond strength which equals or surpasses the strength of the base material.
  • Residential grade PVC membranes typically come in 45-60 mil thickness, while commercial grade membranes are also available in 80-90 mil.
  • Aside from the membrane itself, an insulation layer/board must first be installed to provide a suitable substrate and to help with the energy efficiency of the roof.
  • Can be installed by fully-adhering (gluing) or the mechanically-attached method
  • Expected Life-Span: 15-30+ years 

Modified Bitumen: (FLINTLASTIC)
  • Modified Bitumen systems include factory-fabricated layers of asphalt that are “modified,” using a rubber or plastic ingredient for increased flexibility and combined with a reinforcement for added strength and stability. Bitumen (or asphalt) is a sticky, black, and viscous liquid or semi-solid form of petroleum.
  • In modified bitumen, there are two primary modifiers used today: APP (atactic polypropylene) and SBS (styrene butadiene styrene). APP and SBS refer to the type of polymers that are added to the asphalt. A variety of reinforcements are used with the asphalt, including fiberglass and polyester mats and scrims. Scrim is a reinforcing fabric made from continuous filament yarn in an open mesh construction.
  • Modified Bitumen can be installed as a two-ply or three-ply (multi-ply roof) system. This is a very labor intensive process that absolutely must be performed by a professional.
  • Expected Life-Span: 10-20 years

Industry Credentials

When you’re hiring a contractor to handle anything at your home or business, you want to be certain they’re the most qualified, the most experienced, and the most trusted in their field. That’s a given. Well, St. Joseph’s Roofing is all that and more. Our qualifications include:

Roofing Systems

With the wide range of roofing systems available to residential and commercial customers across Maryland and Northern Virginia, it takes a seasoned professional to know what system is ideal for which situations. At St. Joseph’s Roofing, we bring more than 28 years of experience to every project allowing us to properly match customers with roofing systems. Plus, our industry-leading warranties make our roofing systems an even better fit from a long-term financial standpoint. You owe it to yourself to at least get an estimate from the #1 roofing team in town, so call (703) 716-7663 and start the roofing system conversation with a St. Joseph’s pro!

Our Service List

From top-rated roofing services to siding and gutters, there’s only one contractor in the region that can tackle it all at great prices – St. Joseph’s Roofing. Get in touch today for the best service money can buy. Our services include:

Our Service Areas

St. Joseph’s Roofing services a wide-ranging area in Northern Virginia and Maryland. We have listed all of the counties and cities we frequently service to give you an idea of our reach. If you do not see your location listed, call (703) 716-7663 to see if we can help you.

Counties in Virginia and Maryland:

Fairfax County, Va | Arlington County, Va | Loudoun County, Va | Prince William County, Va | Montgomery County, MD

Cities We Serve in Virginia:

Alexandria, Va | Annandale, Va | Arlington, Va | Ashburn, Va | Bristow, Va | Burke, Va | Centreville, Va | Chantilly, Va | Clifton, Va | Fairfax Station, Va | Fairfax, Va | Falls Church, Va | Gainesville, Va | Great Falls, Va | Lake Ridge, Va | Leesburg, Va | McLean, Va | Middleburg, Va | Oakton, Va | Potomac Falls, Va | Reston, Va | Springfield, Va | Vienna, Va

Cities We Serve in Maryland:

Bethesda, Md | Cabin John, Md | Chevy Chase, Md | Glen Echo, Md | Olney, Md | Potomac, Md | Rockville, Md

#1 In Northern Virginia & Maryland

St. Joseph’s Roofing offers the finest roofing and roofing-related services available in Northern Virginia and Maryland. With more than 25 years in business, we know what it takes to exceed expectations and our results, well, they speak for themselves. Our motto is simple – clients should never be overcharged through deceit. Honesty is the best policy. If that sounds good to you then call (703) 716-7663 for a free estimate today!


Superior Craftsmanship. Award-Winning Customer Service. Honest, Transparent Pricing!

The Most Trusted Contractor In Our Area!

St Joseph’s Roofing is the #1 licensed and insured roofer in Northern Virginia’s for all your residential and commercial roofing needs. Our estimates are free and our work is world-class.

603 Carlisle Dr. Herndon, VA 20170
P: (703) 716-7663

10494 Business Center Ct.
Manassas, VA 20110

3305 Sage Rd
Markham, VA 22643

4533 Stanford St
Chevy Chase, MD 20815

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  • Saturday : CLOSED
  • Sunday : CLOSED

Licensing: VA Contractors License #2705175440 | MD Contractor License #88608
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