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-   -   Flat Roof-Modified Bitumen vs. IB PVC (http://www.diychatroom.com/f9/flat-roof-modified-bitumen-vs-ib-pvc-109286/)

ppowers 06-30-2011 03:38 PM

Flat Roof-Modified Bitumen vs. IB PVC
 
We're replacing our flat roof (SF Bay area) and I'm getting bids for Modified Bitumen roofs as well as a couple of bids for PVC Single Ply. I know I MUST have a reputable roofer but the Modified Bitumens (MB) are quiet a bit cheaper BUT they don't sound like they'll last as long. I'm tempted to go with the IB PVC (80 Mill IB PVC Single Ply Roofing Membrane) but it's SO much more expensive except that the manufacturer states a 25-year warranty. The most I can get from the MB roofers is 12 years. Any comments regarding these different materials. Much appreciated.

Pat

AGWhitehouse 07-01-2011 11:13 AM

I have personally specified both types of these roofs and either one works. The main differences are exactly what you stated. One is cheaper and last on 12 years, the other is more expensive and lasts 25 years.

Alternattive differences are things like the final color. PVC roofs usually come in a white that helps to reflect UV and can reduce the summer cooling costs. Though in the winter it does not assist with heating costs. Modified Bitumen is standard in black and does the inverse of the PVC as far as heating and cooling.

The maintenance difference is that the modified bitumen is usually sealed with a torch by melting the rubber rogether. This helps with repairs because you can easily get a torch and patch in. The PVC utilizes chemical adhesives to bond the plyws together. Without these chemicals, self-patching PVC is hard to do.

Bottom line is: How much do you want to spend and for how long? Are you in a climate that would greatly benefit from the white PVC?

ppowers 07-01-2011 11:33 AM

Is PVC worth it??
 
Thanks for your reply. We live in the San Francisco Bay Area of California in a 2-story house. The top floor is quite hot in the summer and I'm thinking the PVC will help. And we don't use air conditioning in these parts...

I guess my main concern is - I don't know tons of people who have the PVC roof and do they really last? Are they reliable?

AGWhitehouse 07-01-2011 11:39 AM

an 80mil, as you said, should last. Remember that it is not the "field" (the wide open area of roof) that is going to fail first. It is the joints and flashing. So if you get a poor quality contractor it may not last the full time without any issues. If you get a quality contractor you stand a much better chance at having little issue. Installation of flashings and ensuringn proper slopes to drains is key on flat roofs. Standing water will greatly reduce the life span of a roofing system.

ppowers 07-01-2011 12:53 PM

Thanks.

One of my bids has been for a "60 mils ultra ply tpo". Are there advantages of either TPO or PVC?

AGWhitehouse 07-01-2011 01:28 PM

TPO is a popular roofing system. I have specified it as well. the thickness at 60mil is a good, tough, and long lasting thickness.

MB, EPDM, TPO, PVC are all good roofing surfaces when installed right. The advantage of TPO and PVC for you is that they come standard with a white finish which will help in reflecting passive heat gains. There are coatings available for MB and EPDM, but they are an added coating and therefore require additional fees above the standard installations.

I would weigh out your budget with the life span of the system and decide which fits you best. If you are thinking of moving soon go with the shorter life span. If you are there for the long haul, go with the longer life span. Also weigh in who the contractors are and there levels of experience. We used to specify at least 5 years of experience with that particular roofing type to ensure they new what they were doing. Also ask for references and model projects. The model project should be either the one they did 5 years ago or, if they've been in business for a long time, a roof that is 75-100% through it's warranty period. That way you will know if they performed the seaming and flashing correctly.

Lastly, both before you select the contractor and before you give them final payment, ensure that the warranty will be reviewed and approved by the manufacturer themselves. The manufacturer will send a field representative who will inspect all aspects of the roof installation prior to signing off on the warranty. If there are any defficiencies they will require them to be remedied before the warranty will be approved.

Thorough Homework and background checks on contractors is the key to a stable platform for your project to be a success both at the present and in the long run.

Best of luck!!

ppowers 07-01-2011 01:33 PM

Thanks so much, you've been SO helpful!

noe 07-02-2011 12:22 PM

Flat roof Modified Bitumen vs PVC
 
Dear PPowers,
I have a flat roof in S. California. I got modified bitumen in 1995. Warranty was for 5 years. I recently had it inspected and it is still in good shape and does not need to be replaced or repaired. I am in extreme conditions... 105 yesterday, and often there is ice on the roof in the ponding areas in the winter. I was told water shouldn't sit for more than a couple of days. Roofer was supposed to fix low spots but never did. Water has sat for days and still no leaks that I know of. This product has lasted much longer than I ever expected.

Noe

Grumpy 07-06-2011 12:04 PM

There really is no comparison. PVC will outlast modified bitumen hands down. First off you must understand the way low slope roofs are "warranted". There are system specs for 10 year roofs, 15 year roofs, 20 year roofs and 30 year roofs. To date I do not think modified bitumen has a 30 year specification. Why is PV better? PVC will weather better and longer. PVC has fewer seams so less chance of failure, since any qualified roofer will tell you a roof will first fail from its' seams and penetrations.

IB is a good brand of PVC, there are other good brands as well such as Flex which is my personal prefrence. I'm not sure about the IB warranty but you can save a few bucks by downgrading to the 60 mil PVC without much sacrifice in quality. I will tell you the cost savings is NOT in the materials. I compete against cheap A holes every day who constantly under price jobs. Normally they are selling cheap 10 or 12 year rated modified bitumen roofs and cutting every corner possible. I can do a 15 year TPO for the price of a 15 year modified bitumen. I can do a 20 year TPO or PVC for less than a 20 year modified bitumen.

Also you must understand the roof is more than just the membrane. What is involved? How are they flashing the walls? Is anyone installing insulation? How are they detailing the pipes and penetrations? Are they replacing the gutters too? All these things add up. Are they using a garbage chute to drop the garbage 9over 20' required by OSHA but I see guys tossing tear off over the side walls all the time and it's messy as heck!).

Here is a page on my website which may help you understand more about flat roofing options.

Grumpy 07-06-2011 12:09 PM

Quote:

Originally Posted by noe (Post 678529)
Dear PPowers,
I have a flat roof in S. California. I got modified bitumen in 1995. Warranty was for 5 years. I recently had it inspected and it is still in good shape and does not need to be replaced or repaired. I am in extreme conditions... 105 yesterday, and often there is ice on the roof in the ponding areas in the winter. I was told water shouldn't sit for more than a couple of days. Roofer was supposed to fix low spots but never did. Water has sat for days and still no leaks that I know of. This product has lasted much longer than I ever expected.

Noe

The workmanship warranty was for 5 years not the manufacturer system rating/warranty. There IS a huge difference. I commonly install 20 year rated flat roofs very frequently. That doesn't mean I, the roofer, warrant them for 20 years. Depending on how your modified bitumen roof was installed, it could have been rated for 10 years, 12 years, 15 years or 20 years. This would determine how long it should last .

Who made the determination that it was still in good shape? Not saying it's not possible, but in my area I seldom ever see a modified bitumen roof last longer than 12 years. A customer once said to me "We can put a man on the moon, but we can't make a roof last longer than 10 years?" this was in refrence to his roof which he has replaced in 10 year cycles, simply installing modified over modified over modified. WTF?! My reply to him was simply this... "Putting a man on the moon costs billions of dollars. We CAN make a roof last longer than 10 years, but you don't want to pay for it." I lied, I said he was a customer, but he didn't hire me. He was too cheap.

ppowers 07-06-2011 12:27 PM

Thanks Grumpy! You're making a PVC-believer out of me.

Pat

JT168 12-17-2011 05:54 PM

Who and What did you finally choose?
 
PPowers,
I am in SF and confused by the different suggestions too. My neighbor decided to go back to the tried and true tar and gravel.
The bid I got for an IB roofing system was double the highest bitumen membrane roof.
Help! I want to make my decision soon before the heavy rains.

1985gt 12-19-2011 01:34 PM

Quote:

Originally Posted by JT168 (Post 796172)
PPowers,
I am in SF and confused by the different suggestions too. My neighbor decided to go back to the tried and true tar and gravel.
The bid I got for an IB roofing system was double the highest bitumen membrane roof.
Help! I want to make my decision soon before the heavy rains.


Both roofs are a good system. An alternative to asphalt and gravel would be a asphalt roof with a mineral surface cap sheet. The minerals surface is basically the same as the granules on shingles, so they are offered in a number of colors. We have installed some asphalt and gravel roofs that have far surpassed 30 years, the mineral surface do not seem to last as long but I have seen them go 20+. IB is a good roof also, I personally have never installed that brand but we have done PVC and TPO. Depending on material thickness these roofs can go 20-30 years also. Same as EPDM. The biggest thing to look for is a qualified installer. The worst contractor can install the best roof and it will last 5 years, the best contractor can install the "worst" material and it will last far beyond 5 years.

JT168 12-19-2011 11:07 PM

Thank you
 
Thank you for your prompt reply. My roof measures approx 1800 sq ft. The IB estimate came in at a few dollars away from $19,000. It's a lot of money. I have an estimate for $10,000 for a Modified Bitumen w/ 1 ply of 80 lb glass base sheet. He lead me to believe that the modified bitumen will last about 8 - 10 yrs. I was told torch and nail is no good. I had someone come out and recommended a cold peel and stick roof but he did not email me the estimate and did not respond to my follow up email. That made me nervous. I'm not sure what the granule roof is but the bitumen membrane is supposed to be coated with little granules?
I had a new roof leak... then replaced 8 years later with careful screening after calling the local roofing union for some names...and it leaked within months. The same person I referred to my friend before I suffered a leak... had her roof leak within weeks. I agree that I need to find a good company with good workers. Sometimes it's just bad luck too. My rental property has leaked and destroyed the ceilings 3 times since installation. That is why I am so nervous about picking the right one for my home.
THANK YOU!

Hates my roof 12-20-2011 08:08 AM

Sorry to hear about the leaks so soon on a new roof. 75% of all new roofs will leak within 5 years. Even seemingly well established, factory certified roof contractors that take out large ads and have a long list of glowing references to brag about can EASILY botch a given roof job. Hopefully you are not in a rush to get a new roof so you can plan it out and most importantly find a roofer that is both competent and trustworthy - alot easier said than done. Be prepared to reject lots of contractors and be sure to ask them candid questions like "have you ever had any complaints and how did you handle it." etc.


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