Flat roof....will I be sorry?

Hello all,

My wife and I want to build a new home and the home design is quite contemporary and it features a flat roof design. The plan set calls for a membrane roof design that features about a 2% slope to direct water to the drains, the design does not call for any gutters…just the drains. The roof itself is hidden from street view with a 3" parapet, the parapet allows for the roof to have a max peak of 3" at its center points. The total surface area of roof for the house and garage is about 4100 square feet. The garage too is flat roofed with a 3" parapet.

I spoke to a couple of local area architects regarding the roof and one of the architects told me to go with a monolithic SPF roof instead of membrane and prior to meeting him I’d never heard of SPF. The second architect (a much older fellow) told me to “stay away from monolithic roofing systems”. However, he never would tell me why I should stay away…just kept saying “stay away”. The first architect said that SPF was excellent and well suited to our climate (E. Texas) and as a matter of fact his office which has a flat roof is SPF…he told me it was great and had never leaked. He also said that he could do a lot of the maintenance himself because it was easy to walk the roof look from minor damage and “patch” it with an opaque caulk. He told me that with membrane I would not want to try to do minor maintenance myself.

So now I’m pretty confused and concerned that we are making a bad choice if we build this home. Should I absolutely forget about a flat roof home and find a sloped design we love?

Of course this house would be new wood based construction. The roof design is basically 12" thick and is a combination of 2x12’s and various engineered LVL type beams. The roof design features striking overhangs and the drains run down along the exterior walls and puncture through the overhangs. Structurally the design is well engineered.

Our lot is rural and woody with beautiful mature long needle pine trees and miscellaneous leafy trees (oaks, etc). Will a flat roof whether SPF or membrane be too high maintenance and too expensive as compared to a standard pitched roof home with asphalt shingles?

The architect who is recommending the SPF told me that a well done low slope roof is no more likely to leak than a well done pitched roof with asphalt shingles. He said its the roofing job’s quality and execution that is the deciding factor in whether a roof leaks or not. He said “I can take you around town to plenty of homes with sloped roofs that have severe leaking problems”. He said a proper SPF roof will last me the rest of my life and only need to be recoated every 15 years or so. He also said that SPF has a very, very low failure rate.

Here in my area these conditions apply: Hot! Humid! Windy at times (tornado alley and all), fairly rainy most of the year, sometimes we get fairly large hail storms too.

I would really like to know that I have a relatively low maintenance roof no matter what house design I build.

Are there any expert opinions here that maybe able to help me understand my best choice? The SPF over new wood construction sounds appealing, seems to me that it would be quite wind resistant and provide good added insulation. But I doubt there is a perfect roof solution, every type of roofing material must have its positive and negative aspects. I guess at this point I’m stuck in choosing between membrane or spf.

So I’ve rambled on enough here…what would you roofing pros suggest? SPF, Membrane, Other, or all together different house design with sloped roof? I can answer any other questions you may have and could probably post images too if needed.



i hate to say it but i would have to say to go with a completely new slope design. If you have internal drains and alot of trees around like you have said then your gonna spend alot of time clearling the drains. I wouldnt want to test any type of roof constantly under water from clogged drains. Unless you had a hatch to the roof or you dont have a problem climbing up there constantly. If i had to choose a roof type i would go with a rubber torch down roof. Im not a big fan of the SPF but it is not used as much in my part of the country.the few i have seen though have caused me headaches.If you had a sloped shingle roof to a gutter then you could throw up a gutter guard and clean it semi annually.

Stay clear of the SPF roof. The foam isn’t a bad idea, but the coating put on it to keep it watertight must be redone quite frequently (at great cost). Birds love to peck holes in the coating to get into the foam…that means a leak.

Your best bet, if you are not in the sun belt, would be an EPDM rubber roof. Only consider 60,75,90 mil thickness. The thicker the better. It will give you years and years of performance without maintainance.

You should check and clean the drains every year. Get all the debris off the roof.

A flat residential roof isn’t a bad thing. There are millions of them out there doing a great job.


Thanks for the input! I am in the Sun Belt we have long hot, humid summers.

Regarding the EPDM…how does it handle hail? Will the first major hail storm that comes along destroy it the way hail destroys asphalt shingles? Here in E. TX big destructive hail events are not all that rare in the past 3 years we’ve had two, both caused millions of dollars in roof, auto, and other property damage. Will large hail break rupture the EPDM membrane? These large hail crush and destroy asphalt shingles will EPDM perform better in these events? I was under the impression that a foam roof was water proof even without the coating and that the top coat, while water proof too, was really just there to protect the foam from UV light. Thanks for pointing this out to me I was under the impression that the top coat could last for 15 years or so


Thanks for the input! Oh…about the drains in the roof they are not internal they run down the exterior walls of the house like a roof gutter drain does they just don’t hook to a gutter they go straight up through the roof’s overhang. I imagine that they would be removable for cleaning if I so desired. The roof would act as its own gutter meaning that the low points on the roof are just over the outside edge of the house’s exterior walls and the water just follows the drain pipes down.



IB roof or Sarnifil, both are high quality PVC membranes and both should serve you well for many years.
They are white also, so they are more energy efficient.

Or a good 3 ply modified bitumen, torch down.

You will have no problems with your flat roof if it is installed correctly.
IB and Sarnifil have certified installers that do very good work.

The drain issue may pose a problem, but it may not.

Single ply membrane would suit your application perfectly. EPDM is rarely damaged by hail. They make white EPDM now, or you could go the TPO or PVC route also.

Find a certified contractor to do the work, and opt for a factory warranty where the manufacturer inspects the work. This way you are protected.

alot of spf goin on out there.
they do work.
not its biggest fan.
they do work.
yes you rambled.


Axiom, Mayniac, Gweedo,

Sorry 'bout the rambling! But thanks so much for providing some input. I checked out the brands that Axiom suggested and honestly the IB Roofing system looks quite interesting. I’m going to call them this week for more information, etc. I’m not sure I can get an estimate yet since we won’t start to build for about two more months. However, if I can show one of their reps the plan set and get a ballpark estimate I’d be pleased.

I’m thinking that the 80 mil would be my best bet since I’m in hail country. Is this type of material pretty hail resistant?

Thanks again guys!


All roofs have general Maintaining that needs to be done.

All roofs over time may have leak problems, weather is not something we can control. However, we can do preventive maintaining of roof systems.

Hidden gutter and drains can have clogging issues and can be a mess to solve at times, especially in heavily wood areas. Try to look for alternatives. You will thank your self later.

EPDM Roofing is designed for flat roofing, they should hold up to weather like any other roofing product. Some prefer other types.

If you do have a heavy wood lot, keeping the debris off any type roof, or out of gutter systems is a must.
Most people seam to overlook this and end up with problems sooner than what a typical Roofing Job should Last.

Pending the area you are in Typical Roofing lasts 10-15 years.

For Peace of Mind, Look at all your options, pros and cons and you should make the right determination for your needs.


to B.S.

You are on the right track with 80-mil IB.

Cost-wise it will be similar or more than spf, but not by much, especially with a some-what inexpensive Texas labor.

Benefits are great: from Lifetime warranty, to energy efficiency, from longevity to ease of repair.

The architect that likes spf is full of it - how can one suggest a roof solution that is “easy to walk the roof look from minor damage and “patch” it with an opaque caulk”

Sealing the spf roof around rains is a pain, and require the utmost care. With your low wages, roofers tend to spend less time on details.

With IB it is as simple as welding a drain unit to the main membrane and tightening the back-flow gasket.

You will need to clean drains with any flat roof, especially with parapet walls.

If you decide to install a skylight in the future, forget it with spf - you will never seal it properly.

And the whole nonsense with re-coating every 10 years…

If you consider a pitched roof, I recommend an Aluminum metal roof - there are many styles to choose from: Standing seam, wood shakes/shingles, slate, Spanish tile, and on and on…

Stay away from asphalt shingles - in your wooded area they will grow moss which greatly reduces its life.

Also stay away from Epdm in general and white Epdm especially. First, Parapet wall flat roof design just calls for ponding water, and that will void Epdm warranty.

White Epdm usually has a 5 years product warranty. Manufacturers know it will have chalking problems, which will cause seams to come apart.

PS, Epdm comes with “membrane only” warranty unless you buy a ridiculous NDL warranty. I doubt that any Epdm manufacturer even has a residential warranty on material - never mind the seams and labor.

Good luck

I take it you don’t like EPDM? Id put an EPDM roof up against a PVC any day.
And no the major manufactures don’t give residential NDL warranty’s on EPDM, only a material warranty but smaller company’s like mulehide or genflex types probably do offer them.
You can also get a 15 year on white EPDM on commercial work or up to 30 yrs on 90 mil black. And the acrylic paint lasts for many years and stays cleaner/whiter than pvc and tpo.
EPDM and PVC are both proven systems and either if installed properly will service your building fine for many years.

Just to let you know, Genflex is NO MORE. It was bought out by Firestone 2 years ago, so it no longer offers “residential epdm warranty”.

No epdm manufacturer will warranty seams, unless it is NDL, which costs thousands.

Why in the hell would you put an acrylic coating an a brand new roof??? And no, it collects dust just like PVC, and gets dirty the same. Yet to install it right you need few coats and reinforcing tape around all penetrations, which together with Epdm is more expensive than 80-mil IB. Still IB will outlast both epdm and the coating.

And on a personal note, keep doing your Epdm any day over PVC and screwing your customers out of a great energy efficient product, and giving them a roof that 100% dependent on the glue.

Good luck

I just happened upon this thread while doing some research. Don the site administrator is incorrect about the maintenance of coating on an SPF roof. If you use a polyurea top coat you will not have birds pecking thru it. We regularly walk with crampons on our SPF/Polyurea roofs here in Alaska. The polyurea coat is tougher than any coating any one else has offered on this thread. A majority of roofing contractors applying SPF are stuck in 80’s technology and applying inferior top coats, but the new “polyureas” are being used extensively by those in the know. Do some research and you will find pictures of moose standing in pond liners of polyurea without puncturing the top coat. I regularly take my sample of foam with polyurea on it and beat it as hard as I can on whatever sharp corner is available and challenge anyone in the industry to let me do that to their roofing materials. The top coat of polyurea is a must and is the best.

someone likes spf.

give it time.


It depends mostly on the installation crew.

The poster seems to be correct about PolyUrea coatings, because I know several contractors of other Roofing Forums that install the stuff and others that have never seen it, and have used it, and now swear by its toughness.

One of the people I know is a manufacturer of the product and has done extensive SPF Roofs and PolyUrea coatings and I have been taking in all the information I can.



Thanks for all the info. I appreciate it so much.

I called IB Roof and asked some questions but didn’t really get the answers I needed. I was curious to know if the IB membrane (which is a modified PVC) gets brittle and would be especially susceptible to hail penetration. I’m also trying to get a feel for just how thick 80ML is. I should try to get a sample I guess. From the info posted on the IB website this stuff sounds too good to be true…they’re saying that some school district in PA has been leak free for 28 years!! Is that possible?

About my lot it is quite woody but I’ve done a lot of work to ensure that where the house will sit there will be no trees or limbs overhanging the roof but with the wind the roof will collect leaves and have to be kept clear at least twice a year. But to me it sounds no more difficult than cleaning gutters actually it might be easier if I could get up on the roof and walk around with a leaf blower.

The SPF sounds like a good idea to me but it appears that the top coat is the variable here that needs to be carefully considered. I found that in my area (Longview, TX) there is one SPF vendor who advertises their service. Maybe I should call and get some more info.

My house plan calls for a membrane roof with 3" parapet and the plans show that the slope is built up with some type of sloping foam board. Really it looks like a good plan. The house is to have 8 drains on the roof and the garage is specified to have 4 drains. The total area of all roofing to be covered is 4100 SF the garage is about 650 of that and the heated/cooled area is 2100 the remaining 1350 area is over the patio or the house’s generous overhangs.

Does anyone here know how well the 80 mil IB Roof will hold up to large hail? Will it shatter 10 years down the road when hit with large hail because it’s now brittle? Or does it remain pretty pliable indefinitely? Also is the foam board used to create slope a good thing or does it cause other problems?

Thanks again,


Just to let you know, Genflex is NO MORE. It was bought out by Firestone 2 years ago, so it no longer offers “residential epdm warranty”.

No epdm manufacturer will warranty seams, unless it is NDL, which costs thousands.

Why in the hell would you put an acrylic coating an a brand new roof??? And no, it collects dust just like PVC, and gets dirty the same. Yet to install it right you need few coats and reinforcing tape around all penetrations, which together with Epdm is more expensive than 80-mil IB. Still IB will outlast both epdm and the coating.

And on a personal note, keep doing your Epdm any day over PVC and screwing your customers out of a great energy efficient product, and giving them a roof that 100% dependent on the glue.

Its unfortunate your so misinformed about EPDM but insist on spouting off the wrong information. Genflex is Genflex It dosent matter who owns them and it was an example.
No it stays cleaner. No reinforcing tape its not a BUR. If you spray it its only one coat. Im not sure what glue your speaking of but EPDM can be installed mechanically and the seams are taped and are stronger than the sheet itself. If you’d like I could give you a EPDM seminar so you wouldn’t look so silly when your trying to bash it.
If PVC is so great where is trocal or hpg or cooly. Why did firestone quit selling it. Why did I tear off millions of squares of it in the last 20 years? Maybe because its full of plasticizers which leach out over time and is toxic to make or install. And yes EPDM manufactures charge for there warranty’s. Does IB give theres away or is it added into the jacked up price of the material.
I try not to bash other systems and keep thing general they all have there place but to say IB is the the best thing ever come on dude get real its PVC. Nothing new.[/quote]

To BS,

The 28 years old school is actually in Oregon. I have a sample from that roof, after it was removed and had a new IB roof installed last year.

It is a 50-mil and it’s pretty elastic to the touch. I did not try welding to it since i only have one and IB only made about 300-500 hundred of those samples, which are now gone, and i can’t get another one. IB says they welded the new material to that old one and it was just fine.

Here is the image from the front page of our site:


About the hail i don’t know 100% since we do not get hail in New England, but my assumption is that it will not be a problem. 80-mil IB is VERY durable and does not cure so you should be just fine. I mean there is plenty of IB installations in Texas, so you should contact a couple of IB installers in your area, they will show you the product.

You can find a good summary of IB roof here - http://www.coolflatroof.com/ib-roof.php

To Borna:

Man, i’m not misinformed - I do my research. And to me Epdm is not about material warranty (some of it comes with 40 years!) but about seams and energy-efficiency. It sucks in both departments.

If you like Epdm - great. Stick to it. I like IB. I won’t change your opinion, you won’t change mine.

About Cooley - they are located in Pawtucket, RI - 20 minutes from our office :slight_smile: And one of my friends has a furniture warehouse across the street from them.

Cooley was installed on many (if not all) new Target stores built 1-5 years ago (and before i guess).
BTW, they switch from TPO to PVC on and off and change (that is what i was told when i visited them 2 years ago).

Cooley also sells their sheet to Johns Manville (a Berkshire Hathaway company) in is sold as private label by JM.
Don’t know about others.

BTW, there are many Epdm / BUR / TPO / Others, that went under. So your point is irrelevant.

And also, you did not rip a million sq ft. of IB. IB technology is originally from Europe - it was not developed in the US, like most US-produced PVC roofs. I’m sure you know that both TPO and PVC come from Europe, but stuff sold in US is a local blend of chemicals developed in US not so long ago and for the most part is still in development stages (TPO).

Firestone dropped PVC? If they did so ( i’m not sure) it’s most likely pure business - there is more profits in TPO (very cheap raw materials and alot of fillers) and it is easier to sell since it’s cheaper than PVC and almost the same as Epdm.

Coating - there are many ways to install it and many manufacturers. But you still need a reinforcement mesh for any transition like skylights/HVAC/walls etc.

Oh, about the strength of Epdm - man come on - take a piece of it slice the edge of it with a knife and it tears easier than paper where is the strength?

Anyway, enough arguing. Like i said , i like IB and will stick to it.

Good luck

Your right we could go on forever and I dont doubt Ib may be a good membrane.
My point was that epdm has many options. The reinforced sheets are just as strong as other single plys due to scrim.
What would pvc be without its scrim?
Non reinforced epdm will stretch 300 times its size before tearing so it works good on the roof. If you cut pvc it leaks to doesnt it?
Your not supposed to cut your roof with a knife.
Since the introduction of taped seams for epdm failures are almost nonexistent. Even in ponding water.
Acrylic coatings for epdm are tried and true and require no fabric what so ever.
Yes its an extra step but for hot regions it does boost the reflectiveness up to par with the plastics.
In northern regions the cost effectiveness of a white vs black insulated system is minimal if anything.
Firestone also got there pvc from cooly until dropping it a few years ago. I believe manville is having nothing but issues with it now. Everybody’s plastic roof formulations are different some good some not so.
Sorry I guess I couldn’t just let it go. I may have issues.

2ply SBS is my fave for flat roofs. nail a base sheet in the seams, seal them, then torch a cap sheet. quick and easy, never leak unless you forget the mastic around the stacks and vents. epdm is nice, but easy to puncture and repairs are pretty iffy.