What it is
Flat roofing covers any roof with a slope of less than 2:12 (under 10%). Because water doesn't shed the way it does on pitched roofs, flat roofs need a fully waterproof membrane rather than overlapping tiles or shingles. There are four main systems we install in DFW:
TPO (Thermoplastic Polyolefin): Single-ply white membrane. Energy-efficient, good UV resistance, mid-range cost, and the most common choice for new commercial and modern residential flat roofs right now.
EPDM (Ethylene Propylene Diene Monomer): Single-ply black rubber membrane. Durable, long-lasting, and proven — EPDM has been around since the 1960s. Typically black, though white-coated options exist.
Modified bitumen: Asphalt-based membrane reinforced with polyester or fiberglass. Installed as a torch-down or self-adhered roll system. More traditional, good puncture resistance, affordable.
Built-up roofing (BUR): The classic "tar and gravel" roof. Multiple layers of asphalt and roofing felt with a gravel top layer. Still used on some commercial applications, but being phased out in favor of single-ply systems on most new installs.
Best for
Different systems suit different applications.
TPO: Commercial buildings wanting energy savings, modern residential, flat additions on pitched-roof homes
EPDM: Commercial buildings in shaded locations, residential flat sections where cost is a priority, applications where puncture resistance matters
Modified bitumen: Low-slope residential, smaller commercial, applications where the install crew has deep experience with torch-down
BUR: Larger commercial buildings with specific insulation or traffic needs
Key features
What flat roofing systems do well when installed right.
Fully waterproof, not just water-shedding
Long service life with proper installation and maintenance
Reflective (white) options reduce cooling costs significantly in Texas
Can be walked on safely (with some caveats by material)
Compatible with rooftop mechanical equipment, solar, and outdoor living spaces
Material composition
Varies by system.
TPO: Polypropylene and ethylene-propylene polymers, reinforced with a polyester scrim
EPDM: Synthetic rubber (same chemistry as some automotive gaskets)
Modified bitumen: Asphalt modified with SBS or APP polymers, reinforced with fiberglass or polyester mat
BUR: Alternating layers of hot asphalt and roofing felt, topped with gravel or cap sheet
Estimated lifespan
Depends heavily on the material and the install.
TPO: 20-30 years with proper installation
EPDM: 25-35 years, sometimes longer
Modified bitumen: 15-25 years
BUR: 20-30 years
Installation quality matters more on flat roofs than on pitched roofs — a poorly seamed flat roof will leak in the first year, while a poorly installed pitched roof might hold for a decade before failing.
Cost range
Generally less expensive per sq. ft. than premium pitched materials.
TPO: $5.00 – $8.00 per sq. ft. installed
EPDM: $4.00 – $7.00 per sq. ft. installed
Modified bitumen: $4.00 – $7.00 per sq. ft. installed
BUR: $5.00 – $8.00 per sq. ft. installed
Insulation (tapered ISO board for drainage) adds to the cost but is almost always worth it
Maintenance needs
Flat roofs need more attention than pitched roofs.
Semi-annual inspections — spring and fall
Clearing drains, scuppers, and gutters (standing water is the enemy of flat roofs)
Checking seams and penetrations (HVAC curbs, vents, skylights) for separation or sealant failure
Patching punctures promptly — foot traffic and falling debris cause most flat-roof leaks
Recoating (on coated systems) every 7-15 years to extend lifespan
Visual style
Usually invisible from ground level.
TPO: bright white, gray, or tan single-ply
EPDM: matte black (or white-coated)
Modified bitumen: granulated cap sheet in a few limited colors
BUR: gravel-topped, beige to gray
On architectural residential flat roofs, the finish matters more and we'll help select accordingly
Warranty options
Typically longer and more comprehensive than residential pitched warranties.
Manufacturer warranties: 15-30 years depending on system and thickness
"No dollar limit" (NDL) warranties are available on most premium TPO systems
Workmanship warranty through CWT: 15 years
Installation time
Usually faster than pitched roofs of similar size.
Small residential flat sections: 1-3 days
Standard commercial flat roof: varies by size — figure 1-2 weeks for a typical mid-size building
Tear-off and re-roof takes longer than a recover or overlay
Environmental impact
Mixed, depending on the system.
TPO: recyclable, reflective (reduces cooling load in Texas summers significantly)
EPDM: long lifespan, durable, but not reflective in its standard black form
Modified bitumen and BUR: asphalt-based, higher petroleum content
Cool-roof TPO systems often qualify for energy code incentives
Fire and weather ratings
All systems can achieve Class A fire ratings with proper assembly.
Wind resistance: 100-130 mph depending on attachment method
Hail: single-ply membranes are reasonably hail-tolerant but can puncture under severe storms
Class A fire rating available on all common systems
Heat reflectivity on white TPO is a meaningful energy benefit in Texas
Available colors and styles
Mostly determined by the system.
TPO: White (most common), gray, tan
EPDM: Black (standard), white (coated)
Modified bitumen: Black, gray, tan, some granulated colors
BUR: Gravel color (natural beige, gray, white marble chip)
One thing worth knowing before you commit
Flat roofing is more of a system than a single material, and the installer matters more than with pitched roofs. A poorly installed flat roof will leak within the first year — sometimes within the first rain. Seam welding, flashing details, and drain integration are all critical, and there's no room to hide a sloppy install.
The other thing to know is that "flat" is a misnomer. Good flat roof systems have a slight taper built in to drain water toward scuppers or drains. Standing water is the single biggest cause of flat roof failure, and tapered insulation during installation is one of the best long-term investments you can make on a flat roof.
If you're considering a commercial flat roof, want a recommendation between TPO and EPDM for a specific building, or have a residential flat section that keeps leaking, we can walk you through the options and give you a straight answer about what will actually work for your situation.
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