Low-slope and flat roofing systems are the backbone of commercial construction, and they are also found on many residential properties throughout the Dallas-Fort Worth area, from modern architectural homes to patio covers and additions. These roofing systems face unique challenges compared to steep-slope roofs because water does not shed as quickly, ponding can occur, and the membrane must provide a continuous waterproof barrier across the entire surface. At Greenleaf Roofing, we have installed and maintained low-slope roofing systems across Plano and the DFW metroplex since 2013, working with every major membrane type to deliver lasting protection for our clients' properties.
Understanding Low-Slope Roofing
A roof is considered low-slope when its pitch is less than 3:12, meaning it rises less than 3 inches for every 12 inches of horizontal run. Technically, very few commercial roofs are truly flat; most have at least a slight slope of a quarter-inch per foot to promote water drainage. However, the term flat roof is commonly used interchangeably with low-slope roof in everyday conversation.
Low-slope roofs require membrane-style roofing systems rather than the overlap-based systems (shingles, tiles, metal panels) used on steep-slope roofs. The membrane must be continuous and watertight because water may sit on the surface for extended periods rather than running off immediately. This fundamental difference drives the design, material selection, and installation methods for every low-slope roofing system.
Types of Low-Slope Roofing Systems
TPO (Thermoplastic Polyolefin)
TPO has become the dominant single-ply membrane in the commercial roofing market over the past two decades, and its popularity continues to grow in the DFW area.
What it is: TPO is a single-ply thermoplastic membrane typically available in white, gray, and tan. It is manufactured in sheets of 10, 12, or 20 feet wide and various lengths. The membrane is reinforced with polyester or fiberglass scrim for dimensional stability and tear resistance.
How it is installed: TPO can be mechanically attached to the roof deck with plate-and-fastener assemblies, fully adhered to the substrate with adhesive, or ballasted with gravel or pavers. The seams between sheets are heat-welded using hot-air welding equipment, which fuses the overlapping membrane edges into a single continuous piece. Heat-welded seams are among the strongest in the roofing industry, often testing stronger than the membrane itself.
Advantages: TPO's white surface provides excellent solar reflectivity, making it one of the most energy-efficient roofing options for the DFW climate. It resists UV radiation, ozone, and chemical exposure, and it is highly flexible, which helps it accommodate building movement without cracking. TPO is also one of the most cost-effective single-ply options, typically running $5 to $8 per square foot installed.
Limitations: TPO formulations have evolved significantly since the product was introduced, and some early formulations experienced premature failure. Today's TPO products from major manufacturers are much more reliable, but the long-term track record (25-plus years) is still shorter than that of PVC or EPDM. Membrane thickness matters; 60-mil TPO provides significantly better performance and longevity than 45-mil, and we recommend 60-mil as the minimum for DFW commercial applications.
PVC (Polyvinyl Chloride)
PVC single-ply membrane has been in use since the 1960s and has the longest track record of any thermoplastic roofing membrane.
What it is: PVC roofing membrane is a reinforced thermoplastic sheet, typically white, that contains plasticizers for flexibility and UV stabilizers for weather resistance. It is available in thicknesses from 45 to 90 mils.
How it is installed: Like TPO, PVC is heat-welded at the seams. It can be mechanically attached, fully adhered, or ballasted. The installation methods are similar to TPO, and many roofing crews are trained in both materials.
Advantages: PVC has the longest proven track record in the single-ply category, with installations documented at over 30 years of service life. It offers excellent chemical resistance, making it the preferred choice for restaurants, food processing plants, and other facilities where grease and chemical exposure are concerns. PVC is inherently fire-resistant due to its chlorine content, and it provides strong weld seams that maintain their integrity over the life of the membrane.
Limitations: PVC is typically 15 to 25 percent more expensive than TPO. The plasticizers that provide flexibility can migrate out of the membrane over time, particularly in the intense UV and heat conditions of the DFW climate, which can make the membrane more brittle as it ages. High-quality PVC products from reputable manufacturers have addressed this issue with improved formulations, but it remains a consideration for long-term performance planning.
EPDM (Ethylene Propylene Diene Monomer)
EPDM, commonly referred to as rubber roofing, has been a staple of the commercial roofing industry for more than five decades.
What it is: EPDM is a synthetic rubber membrane available in black or white. It comes in large sheets of up to 50 feet wide and 200 feet long, allowing extensive areas to be covered with minimal seams. Standard thicknesses are 45 and 60 mils.
How it is installed: EPDM can be mechanically attached, fully adhered, or ballasted. Unlike TPO and PVC, EPDM seams are joined with adhesive (contact cement or tape) rather than heat welding. This makes EPDM installation less dependent on specialized equipment but also means the seams are generally not as strong as heat-welded thermoplastic seams.
Advantages: EPDM is extremely durable and flexible, performing well across a wide temperature range. It has a proven track record of 40-plus years in the field. The material is highly resistant to UV radiation, ozone, and thermal shock. Large sheet sizes mean fewer seams per roof, and the material is relatively easy and inexpensive to repair. EPDM is often the most affordable single-ply option for large commercial roofs.
Limitations: Black EPDM absorbs significant solar heat, which increases cooling costs in the DFW summer. White EPDM addresses this issue but is more expensive and less commonly stocked. The adhesive-based seams are the primary maintenance concern; they can shrink, peel, or lift over time and require periodic inspection and repair. EPDM is also more susceptible to puncture damage than TPO or PVC.
Commercial or Flat Roof Needs?
Greenleaf Roofing installs and maintains all major low-slope roofing systems throughout the DFW metroplex. From TPO to modified bitumen, we help property owners choose and install the right system for their building and budget.
Schedule a Roof AssessmentBUR (Built-Up Roofing)
Built-up roofing is the oldest flat roofing technology still in widespread use, with a history stretching back more than a century.
What it is: BUR consists of multiple layers (plies) of reinforcing fabric, typically fiberglass or polyester, alternated with layers of bitumen (asphalt or coal tar). The finished roof is topped with a surfacing material, usually a flood coat of asphalt with embedded gravel, a reflective coating, or a cap sheet.
How it is installed: Traditional BUR is installed by mopping hot liquid asphalt between layers of reinforcing fabric, building up a thick, multi-ply membrane. Modern cold-applied BUR systems use adhesives instead of hot asphalt, reducing fumes and fire risk during installation.
Advantages: The multi-ply construction makes BUR extremely durable and resistant to foot traffic and puncture damage. The gravel surfacing provides excellent UV protection and fire resistance. BUR roofs have a long track record of performance, with many installations lasting 25 to 30 years or more. The redundancy of multiple layers means that damage to the surface does not immediately compromise the waterproofing.
Limitations: Hot-applied BUR installation produces significant fumes and requires specialized equipment, making it impractical for some occupied buildings. BUR is heavier than single-ply systems, which can be a concern on older structures with limited load capacity. Locating and repairing leaks in a multi-ply system can be more difficult than with single-ply membranes because water can travel between layers before emerging at a point distant from the actual breach.
Modified Bitumen
Modified bitumen is essentially a modernized version of BUR that combines the proven waterproofing of asphalt with polymer modifiers for enhanced performance.
What it is: Modified bitumen consists of asphalt modified with either APP (atactic polypropylene) or SBS (styrene-butadiene-styrene) polymers, reinforced with fiberglass or polyester, and factory-manufactured into rolls. APP-modified bitumen is heat-welded during installation, while SBS-modified bitumen can be heat-welded, cold-adhered, or self-adhered.
How it is installed: Modified bitumen is applied in two or more layers: a base sheet and one or more cap sheets. The base sheet is mechanically fastened or adhered to the roof deck, and the cap sheet is applied over it using the appropriate method for the modifier type. Self-adhering modified bitumen systems have become increasingly popular because they eliminate the need for open flame or hot asphalt on the roof.
Advantages: Modified bitumen offers the multi-layer redundancy of BUR with easier installation and more consistent quality. SBS-modified products are extremely flexible, which is valuable in the DFW climate where thermal movement is constant. Factory manufacturing ensures uniform thickness and consistent modifier distribution. Modified bitumen is an excellent choice for residential flat roofs, porches, and additions where the scale does not justify a full single-ply installation.
Limitations: Torch-applied modified bitumen carries fire risk during installation and may not be permitted in some areas or on certain building types. Modified bitumen is not as reflective as white TPO or PVC unless a reflective coating is applied over the cap sheet. It is generally more expensive per square foot than EPDM but comparable to or less than TPO and PVC.
Low-Slope Roofing Maintenance
Low-slope roofs require more attentive maintenance than steep-slope systems because of their vulnerability to ponding water and the critical importance of seam integrity.
- Bi-annual inspections: Have a professional inspect the membrane, seams, flashings, and drains in spring and fall. Address any issues before the peak storm and heat seasons.
- Drain and scupper maintenance: Keep all roof drains, scuppers, and overflow outlets completely clear of debris. A blocked drain on a flat roof can cause ponding that overloads the structure.
- Seam inspection: For all membrane types, seams are the most likely point of failure. Look for lifting, peeling, or separation along all seam lines.
- Flashing checks: Inspect all perimeter flashings, penetration flashings, and curb flashings for gaps, cracks, or separation from the membrane.
- Ponding water: If water remains on the roof for more than 48 hours after rainfall, there is a drainage issue that needs correction. Ponding accelerates membrane degradation and adds structural load.
- Remove debris: Leaves, branches, and other debris trap moisture and can puncture the membrane. Regular clearing prevents these problems.
Choosing the Right System for Your Property
The best low-slope roofing system for your property depends on several factors: building use, budget, energy efficiency goals, expected lifespan, and local conditions. In the DFW market, TPO and modified bitumen are the most commonly installed systems, but every property has unique characteristics that may favor a different approach.
At Greenleaf Roofing, we evaluate each property individually and recommend the system that provides the best balance of performance, longevity, and value. Whether you need a new low-slope roof for a commercial building, a flat-roof section on a residential home, or maintenance and repair for an existing system, contact us at (972) 379-9109 or info@greenleaf-roofing.com to schedule your assessment.