Which Roofing Materials Are Best for Flat Roofs?

Flat roofs are a completely different ball game compared to pitched roofs. Over the last 20 years, I’ve worked on hundreds of flat roof installations and repairs, and I can tell you firsthand—selecting the right material is one of the most important decisions you’ll make for the longevity and performance of your roof.

I’m Tim Hauser, a graduate of Arizona State University with a Bachelor of Science in Construction Management. I own a roofing company in Arizona and write for Best Roofing Estimates, where I help property owners understand the options that will protect their investment long term. Whether you’re dealing with a commercial property, a modern-style home, or a multifamily unit, this guide will walk you through the top materials for flat roofs and what makes them a smart choice.

Why Flat Roofs Need Specialized Materials

Unlike pitched roofs, flat roofs don’t naturally shed water. That means anything you install must be waterproof and capable of withstanding standing water for extended periods. Add to that the wear and tear from sun exposure, foot traffic, and sometimes even rooftop equipment, and the need for durable, reliable materials becomes clear.

Flat roofing systems also need to be highly resistant to UV rays, thermal movement, and in many cases, grease or chemical exposure. Let’s take a closer look at the materials that rise to the challenge.

Modified Bitumen: Reliable and Time-Tested

Modified bitumen, or “mod bit,” is an evolution of built-up roofing systems, made from asphalt and reinforced with polyester or fiberglass for extra durability. It’s applied in layers and can be installed using hot torch-down methods or cold adhesive systems.

When Modified Bitumen Makes Sense

This material is a great fit for flat roofs that need long-term durability at a moderate price point. I use mod bit often for clients who want the strength of a traditional build-up roof but prefer a simpler installation.

Key Benefits

• Excellent puncture resistance

• Can be layered for extra durability

• Performs well in heat-heavy climates like Arizona

Things to Watch For

Mod bit can be heavy and labor-intensive to install. It’s not ideal for DIY projects and may require more complex tools and training.

EPDM: The Flexible Rubber Membrane

EPDM is a synthetic rubber roofing material available in large rolls, often black or white. It’s one of the oldest single-ply systems still widely used, and for good reason—it’s flexible, affordable, and easy to maintain.

Ideal Use Cases

I often recommend EPDM for flat roofs on garages, workshops, and multifamily units. It’s also popular for low-budget commercial buildings.

Strengths of EPDM

• Extremely flexible in cold weather

• Easy to repair with patches

• Budget-friendly

Downsides

Its black color absorbs heat unless a white coating is added. Seams can be a weak point if they’re not installed properly or maintained over time.

TPO: The Energy-Efficient Choice

TPO, or Thermoplastic Polyolefin, has grown rapidly in popularity due to its energy efficiency and clean appearance. It’s a white membrane that reflects sunlight and reduces cooling costs—making it a favorite for commercial buildings and hot climates.

Why I Like TPO in Arizona

It holds up exceptionally well under our brutal summer sun. I’ve installed TPO systems that reduced interior cooling loads by as much as 10 to 15 percent.

Top Benefits

• Seam-welded for leak resistance

• Lightweight and recyclable

• Excellent UV reflection

What to Consider

TPO quality varies between manufacturers. Always work with an installer who uses trusted brands and is experienced with heat-welded seams.

PVC: The Premium Performer

PVC (polyvinyl chloride) is another white, single-ply membrane that’s extremely strong and long-lasting. While more expensive than TPO or EPDM, it shines in environments with grease, chemicals, or frequent foot traffic—like restaurant rooftops or commercial kitchens.

Best Uses

I install PVC on buildings that house restaurants, manufacturing operations, or any facility with rooftop exhaust.

Benefits of PVC Roofing

• Welded seams are nearly watertight

• Resistant to chemicals, oils, and grease

• High reflectivity for energy savings

Potential Drawbacks

PVC is more brittle over time in colder climates and comes with a higher upfront cost than some alternatives.

Built-Up Roofing (BUR): Classic and Durable

Built-up roofing is often referred to as a “tar and gravel” system. It consists of multiple layers of bitumen and reinforcing felt or fabric, capped with a gravel or reflective coating.

Where BUR Works Best

I recommend BUR for clients looking for a rugged roof system with excellent insulation and multi-layer protection, especially on large commercial buildings.

BUR Advantages

• Excellent protection from water and UV

• Strong fire resistance

• Long-lasting when installed correctly

Challenges

BUR is heavy, messy to install, and labor-intensive. It also requires proper ventilation and skilled workers to apply each layer properly.

Comparing Flat Roofing Materials at a Glance

Material	Lifespan (Avg)	Energy Efficiency	Cost Range (per sq. ft.)	Notes
Modified Bitumen	15–25 years	Moderate	$4–$7	Good for residential and light commercial
EPDM	20–30 years	Low (unless coated)	$3–$6	Best for cold climates or budget-conscious projects
TPO	20–30 years	High	$4–$7	Ideal for hot climates and energy-conscious buildings
PVC	20–30 years	High	$5–$9	Best for rooftops with chemical exposure
BUR	20–30+ years	Moderate	$5–$8	Great for commercial buildings needing insulation and protection

What to Ask Your Contractor Before Choosing a Flat Roofing System

Before you commit to a specific material, it’s important to talk through a few critical points with your roofer:

What’s the Long-Term Maintenance Like?

Some materials, like EPDM, require regular inspections and patching at seams. Others, like TPO and PVC, are lower maintenance but may be harder to repair if damaged.

How Will This Roof Handle Ponding Water?

Flat roofs are prone to pooling if the slope isn’t properly managed. Ask if the material you’re considering handles ponding well and whether additional drainage improvements are needed.

Will the Material Work With My HVAC or Solar Systems?

If your roof will support solar panels, ductwork, or heavy HVAC units, make sure the membrane can handle that load and any penetrations required.

Choose Based on Function, Not Just Price

When it comes to flat roofs, price shouldn’t be your only deciding factor. Think about what the space is used for, what kind of climate it’s exposed to, and how long you plan to stay in the property. A slightly higher investment in the right material can save you thousands in repairs and replacements over time.

If you’re not sure which option is best, I always recommend getting estimates from qualified professionals who’ve worked with all the major materials. A good contractor will walk you through the pros and cons and help you make a decision based on performance, not just budget.

About the Author
Tim Hauser is a graduate of Arizona State University with a Bachelor of Science in Construction Management. He’s the owner of a successful roofing company in Arizona and has specialized in storm damage repairs, roof replacements, and insurance claim navigation for over 20 years. Tim also writes for Best Roofing Estimates, where he shares practical guidance for homeowners and property managers making roofing decisions.

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