Flat Roof Materials & Installation Costs 2018: PVC vs. TPO, EPDM Rubber, BUR, Modified Bitumen, Spray-on Coating

When it comes to covering up a flat roof, your options are both limited and expansive. What that means in a nutshell is that your traditional roofing materials such as asphalt shingles, concrete tiles, and corrugated metal are out of the window. That being said, flat roof systems such as PVC, TPO, EPDM rubber, and others, each have their distinct pros and cons.

EPDM Rubber installed on a flat roof by GemTile

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So why can’t you put traditional roofing materials on a flat roof? Well, technically you can, but they are almost guaranteed to leak! πŸ˜‰

Systems like asphalt shingles and concrete or clay tiles are installed by overlapping one row on top of another. They work cohesively with the pitch of the roof to shed rainwater and snow as it falls from the sky. Since flat roofs have little to no pitch, the water would work itself underneath the shingles or tiles, eventually rotting the substrate and causing leaks on your interior.

Covering a flat roof is a whole different animal than shingling a pitched one. On a flat roof, generally speaking, you want to avoid any types of seams, if at all possible.

The biggest threat is of course going to be water, which WILL find any access though any hole or inadequately-sealed seams in the roofing membrane.

Your main goal when covering a flat roof is to create a barrier that will be impenetrable to water.

How do you make an item (besides a roof) impenetrable to water? You can either apply something physical such as a tarp, or coat it with a material to create a barrier like you would via deck stain or lacquer. Roofs follow this same premise –- either physically cover it with something like a PVC membrane or apply a coating such as tar or spray on silicon.

Flat Roof Costs:

It’s easy to assume that a flat roof would be far less expensive to apply material to than a pitched one. For access reasons alone it would seem it’s a lot easier to roof a flat surface then one that is steep and requires harnesses and braces to move around.

Install Roof Shingles

$7,500
Average price
Install Metal Roof

$14,500
Average price
Install Flat Roof

$8,225
Average price

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Many roofing contractors will tell you though that working on flat surfaces is actually harder on the back.

Take into account that flat roofs often require the application of adhesives and some types such as modified bitumen are installed with a torch that heats up the seal.

Installation costs can be just as high for a flat roof as they would be a 10/12 pitch.

Labor prices will vary depending on your area. You can get a good idea of the estimated cost to cover your flat roof based on the average material prices.

  • PVC Membrane – aside from the membrane itself, an insulation board must first be installed to help with energy costs. The membrane is installed in rows (6-18′), each of which must be hot-air welded at the seams.

    Many contractors choose to mechanically fasten the edges to help prevent uplift, all of which contribute to labor costs.

    All in total, installation of a PVC membrane costs roughly $7.00 to $10.00 per square foot.

  • EPDM Rubber – manufacturers try to avoid seams with EPDM membrane sizes that can reach 50′ wide by 200′ long. These huge pieces are great for avoiding possible leaks at the seams, but these wide rolls are also very difficult to handle during the installation.

    EPDM membranes install like a giant sticker, but this must be done slowly and with precision to avoid air bubbles.

    Typically, EPDM rubber costs between $4.00 and $7.00 per square foot installed.

  • TPO – insulation boards are first fastened to the roof substrate. TPO also comes in rolls and can be mechanically fastened to the insulation boards or installed with the self-adhesive. Costs are approximately $5.00 to $8.50 per square foot installed.
  • Modified Bitumen – modified bitumen is installed in multiple layers, each of which is torched to the surface below at every ΒΌ turn of the roll. This is a very labor intensive process that absolutely must be performed by a professional. This type of roof does have cold-rolled technologies available now as well, but it involves a lot of application of roofing tar. Estimated costs are $3.00 to $6.00 per square foot installed.
  • Built Up Roof – installation includes applying multiple layers of ply sheets that are bonded together using hot asphalt. The top layer can be a reflective coating for energy efficiency or gravel for added durability. Costs range from $5.00 to $7.00 per square foot installed.
  • Spray-On Roof – applying a spray to a roof sounds easy. The material can be applied right over an existing roof so little to no prep work is needed besides cleaning. It’s still important to apply the spray evenly and delicately though.

    The material itself will also determine the cost as polyurethane foam can be applied for as little as $3.00 per square foot and acrylic $6.00 per square foot.

    Silicon is the agreed upon premier spray application, but the material costs can drive installation prices up to $6.00 to $10.00 per square foot or more.

Choosing an appropriate flat roofing material is a two-part process. On one hand you want a substance that has nice aesthetics while fitting within your budget. You also want to know the product will last:

Materials Life-Span

The life span of your flat roof depends on a lot of different factors starting with proper installation. If your climate has rapid changes that see Spring, Summer, and Winter in the same week, the material will be put under more stress which will reduce its life span. A roof that is accessed a lot will also wear down faster. Here is what you can expect from the popular materials in terms of longevity:

  • PVC – 15 to 30 years.
  • EPDM – 10 to 15 years.
  • TPO – 7 to 20 years.
  • Bitumen – 10 to 20 years.
  • Built Up Roof – 15 to 20 years.
  • Spray-On – up to 20 years.

Why Do Flat Roofs Exist?

Before we get into comparisons of different flat roofing materials, it’s important to know why they exist in the first place since they’re seemingly such a hassle and an almost-immanent leak threat. There are two main reasons behind why a contractor would call for a flat roof: 1) aesthetics and 2) convenience.

For example, when you’re adding on to a home (building an addition) with something like a three-seasons room, a flat roof simply looks nicer. Homes with unblended roof pitches can be an awkward eyesore.

In commercial buildings, flat roofs, outright, offer a more convenient place to install outdoor HVAC units rather than putting them in high-traffic ground areas.

Of course, any roof’s main job is to create a barrier of protection between the building below and the atmosphere above. Therein lies the conundrum associated with flat roofing. For all the aesthetics and convenience, the design doesn’t do a lot to avoid snow and water buildup.

To be fair, flat roofs aren’t completely ‘bubble-level’ flat. They work in much the same way as a gutter system, angled slightly or pitched a couple of degrees, so that water can flow into a downspout. Even so, flat roofing materials need to be able to absorb the brunt of the weather and to withstand ponding water or snow and ice until it melts.

Pros and Cons of Common Flat Roof Membranes

Whether you have a commercial or residential building, some type of roof covering is 100% mandatory. There are generally 5 to 6 different routes to take regarding the materials needed for roofing a flat surface:

1. PVC
2. EPDM
3. TPO
4. Modified Bitumen
5. BUR
6. Spray on Coating

  • PVC Single-Ply Membrane – arguably the most popular of all flat roofing materials (some contractors even install ONLY PVC membranes.) PVC membranes are a single layer of thermoplastic material. PVC roofs are especially strong and durable, featuring a minimum breaking point of 300 pounds per inch compared to the industry-recommended 200 PPI.

    PVC seams are heat-welded (hot air welded) to form a watertight bond. The welded seams are actually stronger than the material itself! Most PVC membranes, especially white-colored ones are very energy efficient, because they reflect the sun’s energy instead of absorbing it.

    PVC membrane can be installed either as a mechanically attached system — using hidden metal plates to secure the hidden or concealed/overlapped parts of the membrane to the roof deck, or as a fully-adhered (more expensive) aka glued onto the roof deck system.

    Most residential and some smaller commercial installations are performed by mechanically attaching the PVC membrane to the roof deck. Both residential and commercial PVC installations often come with lifetime warranties.

PVC flat-roof

Estimated Roof Costs (1620 s.f.)
Asphalt Shingles
Metal Roofing
Flat Roof
$7,500
$14,500
$8,225
See Roof Costs in Your Area
  • EPDM Rubber – commonly known in the industry as a rubber roof. One of the biggest advantages of EPDM over a PVC roof membrane is a much lower price.

    PVC and EPDM typically go 1-2 in terms of popularity for flat roofing depending on what area you live in. The glued-together seams of EPDM are not anywhere as strong as the PVC, heat-welded seams forming a permanent bond.

    Darker EPDM membrane also has a tendency to absorb heat, which can drive up utility bills for the property owner.

EPDM Rubber Roof

Credits: GenTile

  • TPO – another single-ply roofing membrane that chemically bonds rubber, ethylene, and propylene as well as numerous filler materials.

    TPO roofs have been vastly growing in popularity ever since their introduction in the early 1990s. Part of what is fueling their recent rise is energy-efficiency, as they are more readily available in white and light gray (as well as black) compared to their closest competitors PVC and EPDM.

    TPO is said to offer the best of both EPDM and PVC in one package. The material is closer to a rubber roof in cost, but also features welded seems for durability like PVC membranes.

TPO membrane installation[/caption]

  • Modified Bitumen – one negative of TPO, EPDM, and PVC membranes is, although they are durable, sharp objects and collisions can still rip through the single ply of the membrane.

    Modified bitumen features an advantage in this aspect since it is a multi-ply roofing material. A base layer is mechanically attached to the roof deck with plates or bars.

    A ply overlap is then sealed to the base layer with a permanent adhesive. Finally a granule top surface is applied to provide aesthetic and energy efficient properties.

Fusing Modified Bitumen Membrane

Credits: Commercial Roof USA

  • Built Up Roofing (BUR) – better known by their ‘street name’ of tar & gravel roofs, BUR is just that.

    Built up roofing can include up to four plies or more consisting of alternating layers of bitumen (asphalt, coal tar, or other adhesive) with a topping aggregate layer of gravel or other materials.

    Built up roofs have been in use for over 100 years with their biggest advantage being the ability to withstand heavy foot traffic. Membrane roofs are durable… in a sense, but a gravel coating can withstand heavy collisions.

    The downfall is of course the added weight requiring reinforcement to the supporting structure.

bur-roof Credits: Wayne’s Roofing Inc.

  • Silicon Spray – an example of the protective coating installed on a roof is a silicon spray. The biggest advantage of a spray on roof is foregoing any seams like you have with membranes. One would assume that spraying on a roof material would be much less expensive than applying a physical material, but in reality the silicon covering is one of the most expensive roofing procedures.

Credits: Blue Hills Builders

So it’s evident that you have options when it comes to applying a material to your flat roof. How do you make the decision on which type to go with though?

There are some important factors to consider such as ease of installation and how environmentally friendly the manufacturing process is, but for most consumers the two most important decision makers are cost and performance.

Here’s a quick reminder of each material’s pros and cons:

  • PVC Membrane – arguably the most durable of the single-ply membranes with a lifetime warranty, but also very expensive.
  • EPDM – affordable, but not as durable as PVC.
  • TPO – an energy efficient membrane, but a new technology requiring experienced contractors.
  • Modified Bitumen – multi-layers, but also heat absorbing and difficult to install.
  • BUR – compliant with heavy foot traffic but very heavy.
  • Silicon spray – seamless installation, but costly.

To find the perfect flat roofing material you really need to consider the most common issues your roof will face (lots of traffic, volatile climate). You’ll, of course, also have to consider your budget.

So, how will you decide on which roofing material is right for you? It’s recommended to meet with multiple roofing contractors so that they can examine your exact situation and the specific surface needing a coating.

If an old roof just needs replaced it will direct the decision as will if the roof is going on new construction. The contractor will lay out your options, then you’ll find the best choice based on your budget, location, and the ability of companies in your area to adequately install each material.

The end goal is to prevent leaks on a flat roof, luckily you’ve got a lot of different routes that can get you there! πŸ˜‰


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12 thoughts on “Flat Roof Materials & Installation Costs 2018: PVC vs. TPO, EPDM Rubber, BUR, Modified Bitumen, Spray-on Coating

  1. Harold Peters

    My daughter is buying a 60-year-old, 3,000 square-foot, single-level house in southeast Idaho with a 2 to 12 roof over the T-shaped house and a flat roof over the attached garage. While the roof is not presently leaking, it has been patched a number of times and should probably be re-roofed in the very near future.

    We are examining various options and have found your website very informative. We note that you list the longevity of “EPDM – 10 to 15 years.” (https://www.roofingcalc.com/flat-roof-materials/). In contrast, another roofing website claims, “because modern rubber is not susceptible to the sun’s UV and ultraviolet rays, a properly-installed rubber roof can last 50 years or even longer.”

    Obviously, a 50-year roof is much more desirable than one that only lasts for 10 to 15 years. Could you please elaborate on these vastly different longevity estimates. I assume both estimates are based on “properly installed” roofing membranes. Are they addressing the same material?

    This year we have not had a great deal of snow, but last year we had a lot of snow throughout the winter. Do you recommend installing a heated roof to avoid snow standing on the the flat and low-pitched roofs? Does the type of roof membrane make a difference in your recommendation?

    Thank you for your experienced guidance on this.

    Reply
    1. The Roof Guy Post author

      Hi Harold,

      Let me start out by addressing the statement from that other website:

      β€œbecause modern rubber is not susceptible to the sun’s UV and ultraviolet rays, a properly-installed rubber roof can last 50 years or even longer.”

      The answer is not in a million years. The above information is potently false. A rubber roof is glued at the seams and those seams will likely fail within 10 years or so. A costly maintenance will be required to re-glue the seams.

      My suggestion is to consider a hot air welded membrane where the seams are welded together, not glued. PVC membrane is an example of a membrane that forms a permanent bond when the two seams are hot air welded.

      As long as the welding of the seams is carried out to meet the manufacturer’s specs, the roof will likely last 30+ years. I would recommend a minimum of 50 mil PVC membrane such as that supplied by IB roofs. We are not affiliated, but the product is well worth the money, as long as you get the right crew to install it.

      Hope this is helpful.

      Reply
      1. Harold Peters

        Thank you for your response. I guess the adage is still true, “If it sounds too good to be true, it probably is!”

        Reply
  2. 2/12 or less

    I wonder if the technology has improved sufficiently to install asphalt shingles on a roof with a pitch of 2:12 or shallower?

    I know architectural shingles have 30, 35 year warranties and up to 50 non-prorated years if installed by a certified technician. So, why opt for what appears less aesthetically pleasing for a shorter warranty and pay more per square, esp if the prior roof was a traditional asphalt shingle?

    Also, are solar panels better or worse option on these TPO, EPDM, modified bitumen, rolled roofing vs. the asphalt shingle or a metal roof? I’m in Florida about 20 miles from the Atlantic coast.

    Thank you in advance.

    Reply
    1. The Roof Guy Post author

      Asphalt shingles should never be installed on a roof with a pitch of less than 3 to 12. In fact, a minimum slope of 4:12 is probably a much safer bet for installing asphalt shingles.

      At a slope of 2:12, you will have leaks from wind-driven rain in no time, regardless of how good your shingles are. πŸ˜‰

      There are some standing seam profiles that will work on roofs with slopes of 2:12, though.

      Being in Florida, where storms are a clear and present danger, especially in close proximity to the ocean, we would wholeheartedly recommend a fully-adhered vs. mechanically attached PVC membrane such as that from IB Roofs. We are not affiliated with them in any way, but their membranes are absolute best of the bunch for residential and commercial applications. TPO is a distant second, with less-thick membranes and not having the same track record of being proven to be as reliable, weldable, and long-lasting.

      Being in Florida, you will also save a bunch of money and extend the lifespan of your AC by installing a solar-reflective membrane.

      It’s fairly easy to mount PV solar panel brackets on a PVC roof, but I would strongly recommend having the PVC membrane installer on site when the panels are being mounted to ensure the membrane is properly protected during and post the installation of the panels.

      As far as installing PV solar panels on other roofs, you have to drill through the asphalt to install holding brackets.

      On a standing seam metal roof, there is no need to drill the wholes as the S-5 brackets attach to the raised seams of the metal roof, so it’s a perfect system for going solar.

      The pricing numbers in this guide are current, but the costs will vary depending on the roof difficulty, accessibility, and location.

      Reply
  3. Enrique Caro

    I live in Puerto Rico, the epicenter of hurricane activity. Just survived Irma and still struggling with the aftermath of Maria.

    My roof is all cement, flat roof, which over time has become somewhat porous, built in 1989.
    I am exploring sealing alternatives.

    A local contractor offered a system that involves applying an asphalt substrate to the surface, then a membrane which comes in a roll, covered in an aluminum material bonded to an asphalt black laminate. It is applied using a torch. Cost is $2.00 sq. ft.

    Do you have experience with this type of application for a cement flat roof?

    Reply
    1. The Roof Guy Post author

      Hi Enrique,

      I don’t really have experience with the system you describe, but the cost seems good, almost too good.

      Normally, I would recommend a fully-adhered PVC membrane to stand up to hurricanes, but in your case the cost would be disproportionately higher than what you were quoted.

      I would ask about workmanship warranty and how the proposed roofing system will stand up to wind uplift and hurricane winds.

      I would also research the roofing system’s data specs. and call the manufacturer to see if it’s a good fit for the hurricane-prone environment.

      Best of Luck!

      Reply
  4. Terry

    Hi, I have a flat roof with tar and gravel that needs replacing. I have been told I need a torch down type roof which I am not sure is the best. I live in Kelowna, BC where the climate can be very hot in the Summer and very cold in the winter. Not huge daily temperature swings. We need our house reproofed as well as we are building a flat roof garage with deck on roof and walking on deck.
    What would you suggest the type of roof/s I need for the house and deck?

    Thanks,

    Reply
  5. Gary Gummow

    Could I install a single 8′ by 16′ piece of PVC myself on my garage awning? There would be no seams right? Would I have to heat the edges? Thanks, Gary.

    Reply
    1. The Roof Guy Post author

      Hi Gary,

      If you wanted to do it right, you would also have to hot-air weld a small strip of PVC to the dripedge and over the membrane to cover the screw plates which are securing and holding the main sheet of membrane in place. So, to answer your question, a professional installation of PVC membrane will involve at least half an inch of insulation, plates and screws, installing the dripedge, and hot-air welding of the seams.

      I suppose, there is a way you could try to “hack” it, but it would not be a quality PVC install.

      Good Luck

      Reply
  6. Dave

    Appreciate this rundown. I do think the warranties for TPO need to be improved — I see GAF offering 35 years, and I suspect similar offerings from other manufacturers.

    Reply

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