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 said, flat roof systems such as PVC, TPO, EPDM rubber membrane, and others, each have their distinct pros and cons.
So why can’t you put the traditional roofing materials like asphalt shingles on a flat roof? Well, technically you can, but they are almost guaranteed to leak!
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Systems designed for sloped roofs, such as asphalt shingles and concrete or clay tiles, are installed by overlapping one row on top of another. These systems 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.
Did you know? Most flat roofs are not really flat but rather they are low-sloped roofs with minimal pitch. Most “flat roofs” have some pitch (however imperceptible) to accommodate the runoff of rainwater away from the roof, as part of the roof’s water drainage design and to prevent standing water accumulation. Any prolonged ponding or pooling of water on the roof can lead to premature roof leaks.
Covering a flat roof is a whole different animal (specialized skills and expertise are required) than shingling a pitched one. On a flat roof you want to avoid any types of seams, if possible.
The biggest threat is of course going to be water, which WILL find any access though any hole or inadequately sealed seams in a 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 them with something like a PVC or an EPDM rubber membrane or apply a coating such as tar or spray-on silicone.
New Flat Roof Installation Costs:
Most homeowners can expect to pay between $7.50 and 14.50 per square foot to replace an old flat roof on their house with one of the following systems: EPDM, TPO, or PVC membrane. A traditional EPDM rubber membrane would be the least costly option, while PVC with a lifetime residential warranty would be the priciest system to install.
A typical residential flat roof measures between 1,200 and 1,600 square feet, giving you a total replacement cost range of $9,000 to $23,200.
Average Roof Replacement Cost:
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Low End
$8,500Mid-Range
$10,500High End
$14,500 |
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See costs in your area
Aside from the choice of material and membrane thickness, other cost factors are whether the old roof needs to be removed and disposed of, number of layers, condition of the roof deck and whether any additional repairs are needed, level of insulation desired, whether there are any parapet walls to contend with, skylights, etc., roof accessibility, and your home’s location.
It’s easy to assume that a flat roof would be far less expensive to apply materials to than a pitched one. For access reasons alone, it would seem it’s a lot easier to roof a flat surface than one that is steep and requires a harness and a rope line to move around.
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 a layer of insulation, adhesives or hot air welding, and some types, such as modified bitumen, are installed with a torch that heats up the seal.
Keep in mind that installation costs can be just as high for a flat roof as they would be for a steeper roof with say an 18/12 pitch.
Professional warrantied labor prices will vary across different markets in the US. You can get a fairly good idea of the estimated cost to cover a flat roof based on the national averages for most common low-slope roofing systems listed below:
1. PVC
2. EPDM
3. TPO
4. Modified Bitumen
5. BUR
6. Spray-on Liquid Roof Coatings
New Shingle Roof
$7,500 Average price |
New Metal Roof
$14,500 Average price |
New Flat Roof
$8,225 Average price |
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PVC Membrane: Quick Facts and Cost Installed
- PVC, short for Polyvinyl Chloride and Vinyl, is a single-ply thermoplastic roofing membrane known for its superior durability, longevity, and energy efficiency.
- The seams of PVC membrane are hot air welded, creating a permanent bond. The seams are stronger than the membrane itself.
- PVC roofs have been successfully installed on low-slope roofs (both residential and commercial) in the US since 1960s, with many installations known to last over 30 years.
- Residential grade PVC membranes typically come in 50 mil thickness, while commercial grade membranes are also available in 80 mil and 60 mil thicknesses.
- Aside from the membrane itself, an insulation layer/board must first be installed to provide a suitable substrate and to help with the energy efficiency of roof.
- Some installers will employ a fully adhered or glued to the roof deck rather than mechanically attached installation method to help prevent wind uplift. All else being equal, the fully-adhered membrane will cost more than a mechanically attached one.
- The membrane is typically installed in overlapping rows comprised of six-foot-wide PVC membrane, plus an overlap of 6 to 8 inches at each row. Each row of rolled membrane must be mechanically attached and hot-air welded at the seams, with overlapping rows of PVC membrane.
- Immediately next to the roof edge and throughout the outer perimeter of the roof, a three foot wide PVC membrane is used to help mitigate the wind uplift risk.
- The edges of each row are mechanically fastened (using plates and screws) to the roof deck before the seams are hot air welded to help prevent uplift.
- All in total, the installation of a PVC roofing membrane such as the one from IB Roof (residential and commercial vendor) or Sika Sarnafil (mostly commercial and industrial systems vendor) will cost between $8.50 and $14.50 per square foot installed, depending on the installer, membrane type, scope of the project, roof accessibility, and project location.
EPDM Rubber: Quick Facts and Cost Installed
- EPDM, short for ethylene propylene diene terpolymer, is a rubber roofing membrane that is commonly installed on residential and commercial roofs. It’s considered a low-cost alternative to PVC and TPO roofs.
- EPDM rubber manufacturers try to minimize/avoid seams with their EPDM rubber membranes, as seams are often the common points of failure with EPDM roofs. To help mitigate roof failures at the seams, wide span EPDM membranes are commonly used.
- EPDM rubber membrane sizes 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.
- Similar to PVC, EPDM rubber membrane requires a layer of insulation installed in between the roof deck and the membrane for improved energy performance. This is especially important, as EPDM membranes are commonly dark in color and will attract a significant amount of solar radiant heat.
- EPDM membranes install like a giant sticker, but this must be done slowly and with precision to avoid air bubbles.
- Typically, EPDM rubber will cost between $7.50 and $12.50 per square foot installed, depending on the installer, project scope and complexity, and your property’s location.
TPO Roofing Membrane: Quick Facts and Cost Installed
- TPO, short for thermoplastic polyolefin, is a single-ply thermoplastic roofing membrane that offers good overall performance and great energy efficiency for the money.
- TPO membranes are a newer product that made their initial appearance in the 1990s but were plagued by performance issues. Since then, TPO roofs have undergone reformulation and seem to be performing quite well over the last decade or so.
- Similar to PVC, TPO membranes are hot air welded, but the two systems have different chemical composition and hence cannot be combined.
- TPO membrane chemically bonds rubber, ethylene, and propylene, as well as numerous filler materials. In that sense, it’s somewhat closer to EPDM rubber than PVC, although, unlike EPDM, TPO membranes seams are hot-air welded (not glued at the seams).
- Similar to PVC, insulation boards are first fastened to the roof substrate. TPO also comes in rolls like PVC and can be mechanically fastened to the insulation boards or installed with the self-adhesive (fully-adhered).
- Costs are approximately $8.50 to $13.50 per square foot installed, which is slightly lower than PVC. Overall, project costs can range widely, depending on the contractor giving you a quote, project’s complexity, and your property’s location.
Modified Bitumen: Quick Facts and Cost Installed
- Modified Bitumen, an asphalt-based multi-ply flat roof system, is considered a modern take on its close cousin, BUR or built-up roof.
- Modified bitumen is installed in multiple layers (multi-ply roof), each of which is torched to the surface below at every ¼ 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 $7.50 to $13.50 per square foot installed, depending on the project and location.
BUR or Built-up Roof aka Tar & Gravel: Quick Facts and Cost Installed
- Built Up Roofing system is somewhat similar to the modified bitumen, with often an added layer of gravel on top.
- BUR 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 $8.50 to $14.50 per square foot installed, depending on the project size, scope, and location.
Spray-On Roof Coatings: Quick Facts and Cost Installed
- Spray-On Roof coating is a common way to extend the lifespan and improve energy-efficiency of an existing roof.
- Applying a spray coat onto a roof may sound easy. The material can be applied right over the existing roof, so little to no prep work is needed, besides a very thorough cleaning. It’s still important to apply the spray evenly and delicately, though.
- The material itself will also determine the cost, as polyurethane coating can be applied for as little as $4.50 and per square foot. This type of coating is commonly used on commercial flat roofs although it can also be used on large residential projects.
- Elastomeric acrylic coating can be used on both residential and commercial roofs. It’s environmentally friendly and easy to work with. Acrylic coatings can be installed over any flat or slopped roofing surface including EPDM, TPO, PVC, and metal. At the average cost of $4.00 to $7.50 per square foot installed, this liquid roof product delivers solid value for the money.
- Silicone is the agreed upon premier liquid roof coating, but higher material costs and a far more technical and difficult application process can drive installation prices up to $7.50 to $13.50 per square foot or more.
Choosing an appropriate 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 Lifespan
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 – 5 to 15 years.
- TPO – 15 to 25 years.
- Bitumen – 10 to 20 years.
- Built Up Roof – 15 to 25 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 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 standing or ponding water or snow and ice until it melts.
Average Roof Replacement Cost:
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Low End
$8,500Mid-Range
$10,500High End
$14,500 |
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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:
- PVC Single-Ply Membrane – arguably the most popular of all flat roofing materials (some contractors even install ONLY PVC membranes.) for higher-end residential installations 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 permanent, 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.
Metal Roofing
Flat Roof
$14,500
$8,225
- 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 near as strong as the PVC, heat-welded seams forming a permanent bond.
– A darker EPDM membrane also has a tendency to absorb heat, which can drive up utility bills for the property owner.
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 their energy-efficiency, as TPO membranes are more readily available in white and light gray (as well as black) colors 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.
- Modified Bitumen – one potential area of concern with single-ply roofing membranes including TPO, EPDM, and PVC, is that although these roof membranes 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.
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.
Credits: Wayne’s Roofing Inc.
- Silicone Spray – an example of the protective coating installed on a roof is a silicone spray. The biggest advantage of applying spray on a roof is foregoing any seams like you would normally have with traditional membrane roofing.- One would assume that spraying on a roof material would be much less expensive than applying a physical material, but in reality the silicone covering is one of the most expensive roofing procedures.
Credits: Blue Hills Builders
So, it’s evident that you have many 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 recap of each material’s pros and cons:
- PVC Membrane – arguably the most durable and long-lasting of the single-ply membranes, PVC is hot air welded (not glued or torched down), with a lifetime warranty available for residential installations, but PVC is also expensive. Durability and longevity can be further extended with an 80 mil membrane over 50 mil one.
- EPDM – affordable membrane, but not as durable as PVC or TPO. EPDM rubber has a tendency to develop leaks at the seams over time due to glue drying out under freeze-thaw cycles.
- TPO – an energy efficient membrane that is hot air welded (not glued or torched down) like PVC. TPO membranes have had problems in the past, but with a fairly recent reformulation of the membrane, manufacturers claim those problems are now in the past.
- Modified Bitumen – multi-layers, but also heat absorbing and difficult to install.
- BUR – compliant with heavy foot traffic, but very heavy.
- Silicone 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 to be replaced, it will direct the decision, as will the roofing system chosen for a new construction project. 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 system.
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.
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Thank you for your informative website!
I have a small, flat 2nd-story deck/roof (325 sq. ft.) that is currently covered with tar and gravel. It was installed 12 years ago, when this section of the house was added over the garage and some first-story rooms.
The flat roof portion now has a leak, mostly at one end, that has gone through to the dry-wall ceiling in the garage below.
I am considering TPO, but read mixed reviews. I’ve had several roofers look at it. Each wants to do something different (e.g. Modified Bitumen, TPO, etc.). What do you recommend?
Hi Jean,
For a flat roof that may also serve as a deck with foot traffic, IB Deckshield (PDF brochure) would be the best roofing membrane. It’s a PVC membrane with non-slip durable surface designed to accommodate foot traffic. PVC membrane is by far the most practical and durable membrane for low-slope roofs.
If you don’t foresee much foot traffic on the deck, then a regular membrane, such as 50-mil, 60-mil, or 80-mil can be installed, instead of the IB Deckshield. Even the basis (least-costly) 50-mil membrane has a weathering surface that is 156% thicker than the industry standard. You can get a lifetime warranty on residential installation.
No affiliation with IB Roof or any other flat roof material manufacturer.
What to pay attention to in terms of installation: Before a new PVC membrane system can be installed, the old roof will likely need to be completely removed. A repair to the deck, such as replacing any rotten wooden boards may also need to be carried out, as the roof was already leaking.
Removal of the old roof and deck repair may also present an opportunity to replace any wet/damaged insulation near the damaged dry walls. This is a potentially important step to prevent any mold/mildew growth due to any water damage that has been sustained as a result of seeping/trapped water.
Once the roof deck is fully prepared, a layer of insulation will need to be installed in between the deck and the PVC membrane. With proper insulation in place, a mechanically attached (and hot air welded) PVC membrane can now be installed.
Good Luck!
Hello!
The information you provided is very informative and useful. I have a leaking flat roof (new leak last week and only when it rains). It’s a flat torch down roof, 3 years old based on the contractor receipt, unsure if this was a complete replace or just a repair. The roof has 3 layers of plywood and fiberglass, etc. I’ve tried to contact the roof contractor, but he says he’s out of the country.
I have had 2 roofing companies give me quotes:
1. repair the leaking part for $3,500 maybe good for 2 years, $15,500 for complete replacement with TPO, but he was pressuring me to agree without any comparison and no exact numbers and measurements. He just went up the roof, walked around and took a pic.
2. He went up and took measurements and gave me a quote of $17,000 for a TPO roof, showed me samples of the materials to be used (CDX plywood, a waterproof cloth, then the TPO). That’s the cost of the whole project, removal and installation of new roof. They are also offering me a deal to fix the gutters and put leaf guards using Valor. The contractor said they are the exclusive handler for this product across Western Washington. It’s an extra $3,300, but he could off set that.
Do you think those are reasonable prices for both the roof and the lead guards? The company has been in the business for over 10 years. I would love you answer to this as soon as possible because of the urgency of my situation. It’s been raining off and on and every time the rain comes, the roof leaks in drops.
Thank you so much!
Hi Hannie,
It’s impossible to say whether the quote is fair without knowing what were the measurements for the roof. Can you share those? How many stories is the house? How easy is the roof to access? Have you also received any quotes from PVC installers?
Lastly, what part of Western Washington are you located in? Note that local real estate values will influence the price of a roof replacement.
Assuming a low slope roof measuring say 12 to 15 squares, we would expect the total price of roof replacement to be within $10,000 to $15,000 range, depending on the company and where you are located. This figure could vary depending on project specifics.
Also, keep in mind that workmanship warranty is also important to consider. Are you being offered one in writing? It may also be prudent to do some background checks on the company to ensure they have in-fact been in business for 10 years as they claim and that they are properly insured.
Leaf-guards may be more hassle than they are worth, as they still get clogged and you have to clean them periodically, so it might be easier to simply keep the gutters clean. We cover this topic here: https://www.roofingcalc.com/gutter-guard-installation-cost/
So, I would encourage you to ask for a discount rather than including those as part of bundle pricing for the job.
Hi,
I first want to thank you for the incredible amount of information you provide on this website. I came across an inconvenient/unfortunate situation. I recently purchased a home near New York City with a flat roof. It has an approximate 3 year old EPDM roof.
My home inspector did not catch this, but whatever person was on the roof fixing things prior to the purchase put tar on the roof around the skylights and vents. Tar is known to eat through EPDM roofing and is causing leaks through a skylight, as well as the stove hood vents (to my knowledge, hopefully not elsewhere).
I have had several roofers come by, and while they can make repairs, they advise against it as it cannot be guaranteed to fix the leaks. One roofing contractor wants $18,750 for a 60 mil TPO roof and skylights. The other contractor wants $19,500 for 60 mil PVC and skylights. Both are guaranteed for 20 years.
My roof is about 2,000 square feet and has 3 skylights. I don’t know if I should go for TPO or PVC. Am I being ripped off? Please help!!
Hi Seth,
The quoted pricing seems within the ballpark for NYC. You can always ask for a 10% or even a 15% discount, but the key area of focus should be whether the contractor has the experience installing a particular system such as PVC or TPO, with a proven track record of delivering great product and service, as evidenced by happy homeowners who can attest to it.
We would recommend going with a PVC system as such systems have been proven over several decades. TPO is a different system that has seen its fair share of failures in the past, although the current quality is believed to be on par. We would recommend a proved residential PVC option such as that supplied by IB Roof.
We don’t have any affiliation with the company, but it’s the system we have installed numerous times ourselves and seen its durability and longevity in action; performing with flying colors over the last two decades. They have options ranging from 50 mil to 80 mil in thickness. Find out whether the contractor offers workmanship warranty and whether you can also get warranty from IB Roof.
Improperly welded seams would be some of the biggest issues we have seen with PVC installations. That said, if your crew does the job right, a 50 mil membrane should last 20 to 30 years with no maintenance. So, the quality of installation is the key.
I have a 2-story single family home in Brooklyn, NY that has a flat roof with two overhang areas that are shingled.
We are experiencing leaks in a few places, so I called a roofer to check it out and provide options. Without going on the roof, he was convinced that it needed to be replaced for us to avoid further leaks. Here’s what he offered:
1. Strip all layers of existing roof
2. Install plywood subroof
3. Install “rubberized roof system”
4. Install Timberline GAF shingles over the overhang areas
All for a total price of $17,500.
I was also told that the roof doesn’t need to be white for any reason. After reading all the information on this site I’m beginning to think this is a very high quote for a roof option that’s not the best. I’d love your advice and feedback on this. Thanks!
It sounds like the roofer or the salesman is “ball-parking” this job.
It would be more prudent to get a few estimates, so you can have an actual roofing professional (not the salesman) examine the state of the roof and assess the extent of the leaks including potential damage to roof insulation.
Assuming that you have an EPDM rubber roof on the flat portion of the house, the leaks are probably the result of seams becoming unglued and coming apart due to freeze-and-thaw cycles.
Not sure about the age of the current roof, but if this EPDM rubber flat roof is over 10 years old, then replacement does seem to make sense, as repairs would probably only buy you a couple of years of additional service before a new roof needs to be installed.
If the roof has been leaking for a while, there is also possible damage to the roof deck and insulation, that’s why it’s important to have the roof properly examined before an estimate is given.
The roof deck repair/plywood replacement is only needed if the old plywood/roof deck underneath the insulation has been sufficiently damaged by ongoing leaks.
In most cases, such as when the roof leaks have just started, there is normally no need to replace the plywood or wood boards, unless there is a clear evidence of substantial damage to the roof deck.
That said, following the removal of the old rubber roofing system, new insulation ranging from a half an inch to two inches or greater should be put in place.
If there are areas of the flat roof where there is often standing/ponding water accumulation taking place following the rain or snowstorm, then you should probably consider going with a PVC roofing system rather than EPDM rubber. Hot air welded seams of the PVC roof can withstand the accumulation of water on the flat portion of the roof.
Unlike the EPDM rubber roofing system, the hot air welded seams of a PVC roof are not affected by the freeze and thaw cycles, meaning that any pooling water shouldn’t be as big a concern.
Both systems are available in energy efficient colors such as white, but a PVC roof is much stronger system with better seams than EPDM rubber.
Your quote doesn’t say anything about new roof insulation, roof size, and workmanship warranty details. It would be helpful to have that information to make an informed decision.
Good Luck!
First of all, thank you for this helpful and informative guide!
We are a small business owner with a 4000 s.f. office building in the Midwest – Michigan.
We have a flat asphalt rolled roof with three leaks.
We were told the roof was replaced in 2011 and had a repair in 2012 in two places.
Those same two areas (3 x 4) are leaking again, both are just behind the roof top units.
The roof is comprised of four sections being separated by parapet walls.
There is a neighbor’s tree behind us that we may get small branches from periodically. We’ve had three commercial roofing contractors come out.
All three contractors have suggested three different protocols:
1. One says we only need to repair the damaged areas and we could get another couple years out of the roof.
2. The second suggests entire replacement with EPDM – they don’t do any repairs to roofs, just replacements.
3. The third suggested a roof replacement with a TPO roofing membrane, or a roof repair which would last a year, but they will not warranty the repair.
We don’t intend to retire for another 15 years and look to lease the building or sell it at that time.
We’re not sure which is the best option for us and how to best use our small budget. Might you shed some insight?
We were thinking to buy ourselves some time with the repair for now, especially since we’re in the midst of some interior renovation. The renovation is what revealed the leaks.
The cost of the TPO / EPDM vs. rolled roofing doesn’t seem to substantiate itself. Can you please address this as well?
Thank you again in advance, it is truly appreciated.
Here is our view on each option the contractors have presented:
1.
Perhaps the repair could provide a temporary fix, but there is no guarantee, and it may prove too difficult to successfully identify and repair all the roof areas and points of roof failure / sources of leaks.
At best, even if repairs are successful, you will have to continue repairing and ultimately replace the failing roof section in a couple of years.
Our view is that it’s best to avoid additional repair expenses by replacing the failing section of the roof with a better-performing roofing system such as PVC (IB Roofs or Sarnafil by Sika) or TPO.
2.
In our view, this a much better option than a temporary attempt at repair.
We prefer PVC or TPO over EPDM. PVC membrane seams are hot-air welded, creating a permanent bond. EPDM seams rely on a chemical bond (sort of like glue), which can become the likely point of future roof leaks, when seams become unglued overtime due to multiple freeze and thaw cycles.
3.
Again, we like TPO with its hot air welded seams better than EPDM rubber, which relies on tape based on glue.
Rolled asphalt is the least expensive and least reliable roofing option for low-sloped roofs, hence the difference in price you see.
Our view: If you are not ready to replace the entire 4,000 s.f. of roofing, then replacing one section of the roof at a time is the way to go.
We have a round house, 36 feet in diameter – 1000 sq. ft of roof with a pitch that is between 3/12 and 4/12.
It currently has a bitumen roof that has 1.5″ of foam insulation on top of the decking and then the bitumen roofing (36″ wide) was rolled out over the top with the seams overlapped and welded.
On top of this was spread roofing tar and then about 7 tons of gravel as ballast. The roof is 21 years old and we have experienced a slow leak that has caused damage and so we are trying to decide between repair and replacement.
We live in the mid-Atlantic region outside of Washington, DC. I am reading through the various options and am intrigued by a PVC roof.
Do you think that would be a good option for us or should I be looking at other materials/processes?
Thanks, Krister
Hi Krister,
Our view is that a PVC roofing membrane, whether mechanically attached, or fully-adhered (if you are concerned about hurricane winds) would be a sound choice for a round house and a roof such as yours.
Removing the old roof will be expensive, but the new PVC roof (50 mil to 80 mil in thickness) should prove to be a smart investment when done right.
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.
Hi Harold,
Let me start out by addressing the statement from that other website:
“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.”
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.
Thank you for your response. I guess the adage is still true, “If it sounds too good to be true, it probably is!”
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.
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. 😉
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.
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?
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!
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,
Hi Terry,
For the flat roof deck, you can use a specialty PVC membrane product called Deck Shield by IB Roofs.
For the main roof on the house, you can go with their cool roofing membrane installed over insulation: http://www.ibroof.com/pvc-roofing-membranes/
Good Luck!
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.
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
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.