If you’re starting to have issues with your flat roof such as warps, rips, or tears, it may be time for a roof replacement.
To get the best results when replacing your flat roof, you’ll need to know what type of material to use and how it’ll fit into your budget. We’ll take a look at the absolute best flat roof materials for your home or business, and discuss the costs, pros, and cons you can expect. But first, here’s what you need to look out for when considering these options.
What to Consider When Choosing Flat Roof Materials
Pitched roofs have a physical advantage over flat roofs in their ability to let rainfall cascade down into gutters for drainage to the ground. Therefore, pitched roofing materials like asphalt shingles are engineered to ensure water flows well over the surface. Flat roof shingles aren’t as efficient when it comes to protection from the elements, as water tends to seep between each shingle and can penetrate your roof membrane.
Flat roof systems tend to be more affordable than pitched roofs. Flat roof costs hover around $12,000 for a full installation. But Mike Reedy, Owner of Quality Built Exteriors, states “many contractors try to save even more money on low-slope roofs by using shingles, instead of more reliable products like rubber EPDM, PVC, or TPO membrane. This is a mistake and almost always leads to leaks in just a few years."
Flat roofs aren’t just susceptible to leaks, they can also develop other problems such as alligatoring, blistering, bubbling, and sagging. So it’s important to choose the right roofing materials in order to avoid or delay these issues throughout the roof’s lifespan. Below, we review the best flat roof materials to help you decide which one is right for you.
The Best Flat Roof Materials on the Market Today
PVC roofing
Installed cost per square foot: $4 - $12
Polyvinyl chloride (PVC) roofing membranes have been heralded as one of the best flat roofing materials in the single-ply roofing industry. The material uses processed petroleum or a natural gas and salt mixture. It comes in big rolls with a bottom ply, a flexible fiberglass mat, a weathering film, and an acrylic finish.
Pros of PVC roofing
Let’s explore why they’re one of the best options for most flat roof applications:
Long-lasting - PVC roofs are strong and very durable. They have a minimum breaking strength of 350 pounds per inch. That’s well above the 200-pound-per-inch standard in the roofing industry.
When installed properly, PVC lasts up to 30 years on a flat roof and doesn’t need much maintenance.
Resistant - PVC roofing has a strong fire-resistance rating, and its welded seams make for superior wind uplift resistance. If your region is prone to strong winds, PVC membranes are a smart choice.
Waterproof - There’s a reason PVC pipes have been used for decades to carry water around. They don’t easily leak. When using the same material on your flat roof structure, you can count on watertight performance even if you experience temporary ponding or even exposure to plants and bacteria.
When the sheets of PVC are rolled out, the seams are sealed with hot air. That makes PVC roofing membranes virtually impermeable to water.
Energy savings - Because PVC membranes come in white, they reflect most of the intense sunlight throughout the day. Since your building will not need to do as much work to cool itself, you’ll save a substantial amount of energy, and money. As an added benefit, the vinyl can be recycled after serving its life on your roof instead of winding up in a landfill.
Color options - PVC comes in several different colors. While white may make the most sense in warmer climates, you can go with shades of tan, brown, or gray to match the natural surroundings. You can also select a darker hue to save more on heating in the winter.
Cons of PVC roofing
Toxicity - PVC membranes contain orthophthalate plasticizers which can leach out when rained upon, potentially contributing to environmental pollution due to runoff water.
Replacement complexity - When restoring an old roof with PVC, more labor and care are required to completely remove the old roof material. Any debris or sharp material can puncture through the underside of the PVC and cause future leaks.
Built-up roof (BUR)
Installed cost per square foot: $3.50-$10
Built-up roofs (BUR) are made out of layers of materials bonded together by asphalt and hot tar, then topped off with rocks or gravel. It’s like putting multiple roofs on top of each other for more protection.
Ballasted roofs use bigger rocks that hold the waterproof membrane in place underneath, whereas tar and gravel roofs use smaller rocks that are sealed down using a liquid that hardens as it cures, or with a blowtorch that hardens the material.
Pros of a built-up roof
Safety - If you have lots of foot traffic or mechanical systems on your roof, BURs make it safer for maintenance staff to walk around as foot traction is superior to other roofing options.
If a neighboring structure is on fire, there’s a low chance a BUR will catch fire. The top layer of built-up roofs is made from several layers of rocks, so it’s less likely to catch fire.
Longevity - Each layer of material you add to your built-up roof will extend its life by about 5 years, and since BURs require 5 layers, you can expect to get about 20 to 30 years of longevity.
Strong seal - Since the roofing material is layered over itself, there are no seams to worry about being sealed with a torch or glued down. That means a strong seal you can trust.
Hail? Who cares? - Any kind of flying debris like hail or downed tree branches won’t be an issue. The thick layer of stone and gravel is a strong shield for your roof membrane.
Cons of a built-up roof
Weight - All those layers of roofing material plus the stones on top are heavy. Especially if you’re using a ballasted roof, you need to make sure your underlying roofing structure is strong enough to withstand this pressure.
Installation speed - Layering fabric, heating bitumen, waiting for it to cool, and layering an additional layer takes a long time. Now, multiply that process by 5 other layers, and you can see that a BUR will take a lot of labor hours to complete. That can be costly, relative to other roofing material options.
Leak repair - If you see the interior of your BUR roof leaking, finding the location of the leak can be a challenge since the surface of the roof is covered in rocks or gravel, so the process is more time-intensive than with other types of roofs. Your roof repair technician will need to dig out a large depth of rocks to find the source of the leak, making for a potentially frustrating and costly repair.
TPO roofing
Installed cost per square foot: $4 - $14
Thermoplastic polyolefin (TPO) is made up of polypropylene and ethylene-propylene rubber. This single-ply membrane deflects the sun’s heat due to its bright white color, and repels water thanks to its slippery surface, making it an excellent material for your flat roof.
Pros of TPO roofing
Cost - With many of the same benefits as PVC, like its heat-reflective white coating and heat-sealed seams, TPO roofs come in at a more budget-friendly installed cost of as low as $4 per square foot.
Energy savings - TPO roof coatings are white, which allows them to reflect heat and keep the surface temperature lower than that of a dark roof. For commercial buildings, air conditioning can be a huge cost. That makes TPO a smart choice for building operators and owners who have an eye on their long-term budget.
Weight - TPO is a single-ply, lightweight material that performs well over time on low-slope roofs. It weighs an average of just half a pound per square foot, making it an excellent choice for older structures that may not be able to withstand the pressure and load of a built-up roof.
Cons of TPO roofing
Maintenance - Repairing a TPO roof usually requires a heat welder and professional expertise. Moreover, TPO can become slippery in snow, rain, or frosty conditions. This isn’t a DIY-friendly flat roofing material to work with, so it’s best to work with a roofing contractor to solve any maintenance issues.
Heat and fire resistance - Seams on TPO roofs can bust, crack, and leak when the temperatures get extreme up on your roof. The top laminated layer of TPO roofs has shown inconsistent performance in these conditions across vendors. Moreover, TPO is not as fire-resistant as PVC in field tests.
Rubber roofing (EPDM)
Installed cost per square foot: $4.50 - $14
Ethylene propylene diene monomer (EPDM) really should be abbreviated EPDT, since the roofing material is no longer a monomer, it’s a terpolymer. Since this rubber roofing material has had a long history, the name stuck.
EPDM is a very durable synthetic rubber roofing membrane. It’s made out of an oil and natural gas mixture and installed either with liquid adhesive, screws, or ballasted with gravel and stones.
Pros of rubber roofing (EPDM)
Longevity - A properly installed EPDM roof will last much longer than other flat roofing options - up to 50 years!
Ease of installation - EPDM material comes in large single-layer rolls which are easy for your roofing contractor to work with. The rubber membrane is elastic and flexible and you don’t need to use blowtorches to seal the seams together.
Resistance to the elements - Since rubber is elastic, it naturally expands in the summer and contracts in the winter. It can withstand temperature extremes easily without wear. Rubber is also a fire retardant and naturally impact resistant.
Affordability - With the average installed price per square foot ranging between $4.50 and $14, this roofing option is a very affordable flat roofing system.
Easy repairs - Unless using a ballasted system weighed down by lots of rocks, it’s straightforward to find roof leaks and repair them.
Cons of rubber roofing (EPDM)
Shrinkage - While EPDM is easy for roofers to install, the seams can break apart and the rolls are more prone to shrink away from each other, exposing the roof underlayer. If not installed properly, EPDM roofs can leak in a very short amount of time. That’s because the glue holding the material down is not welded like a TPO roof. This is more of a risk on larger, industrial-sized installations than on smaller roof types.
Heat - Most EPDM rubber is black. In the summer, it will absorb heat from the sun and lead to higher building cooling costs.
Aesthetics - A rubber roof doesn’t look pretty. It’s made out of the same rubber weatherstripping material found on car doors. If you’re looking for a sleeker look, TPO or PVC would be a better option.
Modified bitumen roofs
Installed cost per square foot: $4-$8
Modified bitumen is a single-ply rolled roofing system made from asphalt with added polymers. It has a base waterproofing layer and a surface layer that bonds to a material that resembles regular asphalt shingles. Europeans invented this roofing system in the late 1960s and it’s relatively easy for homeowners to install on smaller roofs.
Pros of modified bitumen roofs
Aesthetics - There are as many color variations of modified bitumen roofs as there are composite shingle types. That means you can easily select a variety of materials to match your building exterior, which may have parts that are covered by asphalt shingles.
Installation ease - Modified bitumen now comes in rolls that have a self-adhesive, sort of like a sticker sheet. That makes it easier, safer, and less smelly than having to use a torch-down method to heat seal the material to your roof membrane.
Seal to the roof - There are no seams to worry about with modified bitumen roofs, so you have a superior waterproofing solution that is leak-proof.
Cons of modified bitumen roofs
Fragility - Other roof types are more resistant to hail and falling branches than modified bitumen roofs. The material is fragile enough to be broken when installers simply walk around on your roof.
Longevity - Modified bitumen roofs can last as little as 10 years before they need to be replaced. Because TPO or PVC hold up much better to standing water in puddles than modified bitumen, you may want to consider those options instead, especially if you live in a region with consistent seasonal rainfall.
How to Choose the Best Flat Roofing Material for You
There are pros and cons to any roofing material, and flat roofs are no exception. Whether you’re looking to replace your flat roof on your home or commercial building, choosing between aesthetics, energy efficiency, longevity, and resistance can be overwhelming, especially when it comes to such a large investment and long-term commitment as a roof replacement.
If you’re unsure of which material to go for, you can always consult with a professional so they can assess your particular roofing needs and advise you accordingly.
Adam Graham is a construction industry analyst at Fixr.com. He has experience writing about home construction, interior design, and real estate. He communicates with experts and journalists to make sure we provide the most up-to-date and fact-checked information. He has been featured in publications such as Better Homes and Gardens, and written for various outlets including the National Association of Realtors, and Insurance News Net Magazine.