Time to replace your flat roof? Trying to determine the best waterproofing applications or roofing materials to consider?
A flat roof replacement is a little different than a standard roof replacement. Water can’t run off a flat area like it does standard roof pitches, so it needs something waterproof.
The problem is knowing which waterproof material to choose from all the option available.
For over 35 years, Bill Ragan Roofing has helped homeowners find the perfect material fit for their specific roof replacement needs. So, let's dig into the best waterproofing applications/roofing materials available for a flat roof.
By the end of this article, you'll learn the answers to:
Flat roofs can't have standard asphalt shingles, which is why there's needs to be some form of waterproofing. While there are plenty of waterproofing applications, there are three specifically for residential roofing that standout.
Let’s get to the three best waterproofing applications for your flat roof.
PVC roofing membrane (polyvinyl chloride) is a single-ply white membrane used in commercial and residential roofing. As long as it's properly installed, you should get around 25 years out of a PVC flat roof.
The white color of the membrane makes PVC a great choice over a bedroom or living area because it’ll keep the room below cooler during summer. However, you do need to consider that it'll get dirty over time.
While the “dirtiness” won’t affect the functionality, it's very noticeable if you can see it from a window. So, you don’t have to worry about this if aesthetics aren’t a big deal or you can't see the roof.
However, you still need to consider it when making your final decision.
TPO roofing membrane (thermoplastic polyolefin) is a single-ply white membrane used in both commercial and residential roofing. Like PVC, it has the benefit of a white membrane that reflects heat.
Besides the chemical makeup, PVC is so similar to TPO that the untrained eye can’t tell the difference. The installation process for both is even pretty much the same.
The white also makes a TPO roofing membrane a great option for a flat roof over a living space. Just remember to consider how dirty the white gets as it ages and how it looks when seeing it from the window.
However, the only big difference is that a PVC roofing membrane is more flexible than TPO. You can expect to get around 25 years out of a TPO roofing membrane as long as it’s installed properly.
EPDM roofing membrane (ethylene propylene diene monomer) is a synthetic rubber black membrane that’s mostly installed on commercial and medical facilities. However, EPDM is becoming more and more popular in residential roofing.
Unlike the white of TPO and PVC, the black membrane absorbs heat instead of reflecting it. So, I don't recommend using it over a bedroom or living space.
However, you can still install it over a bedroom or living roof and add things like insulation to help. The big benefit an EPDM roofing membrane has over PVC and TPO is that it’s extremely durable, and I like to say it’s like having a bulletproof rubber roof.
This durability means you can expect to get around 25 to 30 years out of a fully adhered 0.060-thickness EPDM roofing membrane.
Including labor and materials, installing a membrane roof system on a flat roof will cost around $12.00 to $17.00 per square foot in 2025. Obviously, the size of the roof determines where you'll fit in the price range.
However, the cost per square foot will trend towards the higher end of the price range on smaller projects. This is because roofing membranes come in rolls, so smaller roofs require more cutting, fitting, and other finer details to prevent leaks.
With that in mind, the table below gives you a better idea of membrane roofing's cost based on the area's square footage.
Square Footage |
Membrane roofing cost in 2025 |
| Under 500 square feet | $17.00 per square foot |
| 500 to 1000 square feet | $14.00 per square foot |
| Over 1,100 square feet | $12.00 per square foot |
Just keep in mind that it’s impossible to give you an exact price due to all the different cost factors. The membrane you choose, roofing contractor you hire, and your area's supplier prices play a huge role in the cost, but there's much more.
Labor costs are factored into every line item on an estimate. So, if anything takes time and labor, it adds to the labor costs of a flat roof replacement.
Unfortunately, there’s no set price for labor and time because it depends on the roofing contractor you hire. But the more manpower and time it takes to replace your roof, the higher the cost.
As I've already mentioned, the square footage of the roof plays a huge role in a flat roof replacement's cost. It affects the amount of materials used, labor, and time needed to complete the job.
I say square footage because it’s what homeowners are familiar with. However, you’ll also hear a roofing contractor say “price per roofing square” (100 square feet).
While it plays into square footage, whether the roof is residential or commercial can affect a flat roof replacement's cost. Remember, the cost per square foot will trend towards the higher end of the price range on smaller projects.
So, commercial roofs actually end up being cheaper per square foot than residential roofs. This doesn't mean it'll be cheaper overall, but residential roofs are more complex and require more attention to detail that usually increase labor costs.
A big cost factor is the type of insulation and amount being installed under the roofing membrane. Insulation that’s thick enough to insulate the entire structure costs more than using fabric insulation and gluing the membrane to it.
Another thing that always factors into pricing is the other components that are included with a membrane roof system. However, this depends on how the membrane roof system is being installed.
During the tear-off process, the old roof and other components are ripped up until there's only a clean roof deck. So, there will be a labor cost associated with tearing off the old roof.
However, the torn off debris also must be loaded into a dump truck or trailer to be taken to a dump of the contractor’s choice. The dumpsites charge significant fees for this service, so there will also be a dump fee and labor cost for the crew member(s) doing the work.
A roof penetration is anything that comes through your roof, like plumbing vents, gas vents, kitchen/bathroom vents, skylights, and chimneys. The more penetrations your roof has, the more it impacts the cost.
This is especially true for flat roofing, which doesn't have enough pitch to drain. Smaller pipes or vents won’t impact much, but skylights and chimneys add more to a new roof’s cost because they take longer to flash and work around.
After reading this article, you should have an idea which one of the best waterproofing applications is right for your roof. There are other options out there, like modified bitumen.
However, these are the three I recommend to homeowners who want a quality waterproof roof system. However, flat roofing is specialized and unique, so you need to hire a great roofer with the right experience.
This is a crucial decision that you can’t take lightly, especially when it comes to waterproofing. That’s why I wrote another article with the 9 tips you need to hire a great roofing contractor for your flat roofing project.
Check out 9 Tips for Hiring a Great Roofing Contractor to avoid making the wrong hiring decision for your flat roofing project.