| Author |
Message |
David Axt, AIA, CCS, CSI
Senior Member
Username: david_axt
Post Number: 1296
Registered: 03-2002
| | Posted on Monday, May 07, 2012 - 01:03 pm: |    |
I am currently evaluating PVC (Sarnafil) and KEE (Fibertite) roofing membranes. The problem is that each membrane manufacturer tests to a different ASTM standard.
Sarnalfil uses ASTM D638 - Standard Test Method for Tensile Properties of Plastics.
Fibertite uses ASTM D751 - Standard Test Methods for Coated Fabrics.
How do I evaluate breaking strength, elongation, tear strength, etc. in an "apples to apples" fashion? |
John Bunzick, CCS, CCCA, LEED AP
Senior Member
Username: bunzick
Post Number: 1391
Registered: 03-2002
| | Posted on Monday, May 07, 2012 - 01:47 pm: | |
You can't, really. However, I will say that I have specified these two products "against" each other on several occasions. That is, the contractor could select whichever of the materials (among manufacturers I listed) they wanted. |
ken hercenberg
Senior Member
Username: khercenberg
Post Number: 219
Registered: 12-2006
| | Posted on Monday, May 07, 2012 - 02:18 pm: | |
I've done the same as John. Both manufacturers seem okay with this. |
David Axt, AIA, CCS, CSI
Senior Member
Username: david_axt
Post Number: 1297
Registered: 03-2002
| | Posted on Monday, May 07, 2012 - 03:49 pm: | |
What membrane thickness did you specify? |
ken hercenberg
Senior Member
Username: khercenberg
Post Number: 220
Registered: 12-2006
| | Posted on Monday, May 07, 2012 - 04:04 pm: | |
I'm partial to minimum 60 mils (15 mm) for most conventional systems and 80 mils (20 mm) for PRMA and green roofs. I like going with Sarnafil's self-adhering membranes, G410 at conventional and either G410 (roofing membrane so it can be left exposed) or G476-20 (waterproofing membrane must be concealed).
Fibertite will tell you that you can specify their 45 and 60 mil membranes instead due to the KEE. That may be true. I prefer to have the Contractor submit that as a substitution request or as a voluntary alternate so the process is fully documented. |
David Axt, AIA, CCS, CSI
Senior Member
Username: david_axt
Post Number: 1298
Registered: 03-2002
| | Posted on Monday, May 07, 2012 - 04:34 pm: | |
The FiberTite rep is saying that their 45 mil membrane is equivalent to Sarnafil's 60 mil membrane. I don't believe it and wish I had equal ASTM testing data to back up my assumption. I believe the FiberTite rep is trying to get an economic advantage over Sarnafil.
I specified FiberTite's 50 mil membrane and the FiberTite rep claims this membrane is equivalent to Sarnafil's 80 mil membrane, not the 60 mil membrane I specified. |
J. Peter Jordan, FCSI, CCS, AIA, LEED AP (Unregistered Guest)
Unregistered guest
| | Posted on Monday, May 07, 2012 - 03:38 pm: | |
The thermoplastic roofing membranes are so difficult to compare, and I am afraid that I really don't understand how some of this stuff relates to overall performance anyway. I have uplift performance requirements (FMG requirements if applicable), a minimum thickness, warranty requirements, and (more and more) emittance requirements. I may have a preference for installation. But I would much rather qualify installers, looking for the ones that qualify for the longest warrantees.
If I have a performance tested system, do I really care about the chemistry of the product? I know this is somewhat heretical, but... |
ken hercenberg
Senior Member
Username: khercenberg
Post Number: 221
Registered: 12-2006
| | Posted on Monday, May 07, 2012 - 06:34 pm: | |
Not at all Peter, but the industry has not found a way to provide us with an 'apples-to-apples' end result so we're left with our experiences and our preferences.
Some of the old BUR systems were marketed based on their tensile strength because that was their weak point. Did a 'good' 3-ply system work as well as a 'fair' 4-ply system? Not in my book but the marketing folks sure pushed the point.
Manufacturers can make their EPDM and TPO systems comply with all kinds of tests but I still don't feel comfortable specifying them unless specifically directed by clients, and even then I'm 'kicking and screaming', well figuratively anyway.
I agree that good relationships with manufacturers and installers can be among the best ways to pick systems, but that's not always feasable.
David, I'd try to find a way to require Fibertite to prove that they're equal to your liking. They have told me that they can't bid based on thickness because their product costs more than Sarnafil. I've told them that I'm already using a plastic sheet about the thickness of a quarter (60 mils). I'm not about to 'change down' to a dime (45 mils). |
Alan Mays, AIA
Senior Member
Username: amays
Post Number: 76
Registered: 02-2003
| | Posted on Monday, May 07, 2012 - 06:52 pm: | |
Ken, I am partial to a Mod Bit roof. BUR is becoming a rarity these days. Siplast and Soprema have performed well as much as others. I have done PVC, EPDM, TPO, etc in the single plys. I will have to say all have performed well. The thing with BUR is the labor. I used to be the same way about the single ply as you are. I would kick and scream about it. The thing that changed my mind was a BURSI class I took and it was stated by a Mansville rep, that he has to realize that he has to compete with single ply, as there are 50+ year old EPDM roofs that have performed without a problem. |
ken hercenberg
Senior Member
Username: khercenberg
Post Number: 222
Registered: 12-2006
| | Posted on Monday, May 07, 2012 - 07:34 pm: | |
Sure, but there are also 50 day old roofs that are failing as we speak. Which do you think are prevalent? No offense meant, but you also have to consider the source. At least non-EPDM roofs can be tested using electric field mapping which, BTW, I recommend on all roofs where practical.
I too prefer mod bit and hot-rubberized asphalt systems but try to get owners to realize their value; heck try to get architects to understand that these may be worth fighting for. In many cases you can save money by using them if designed properly, but that's another discussion. BUR is, IMHO, almost gone from the industry. If the 'green' movement has its way, mod bit and hot rubber will soon be gone as well. So will PVC and KEE. That will leave us with little of value at this point from my point of view.
The lunatics have taken over the asylum. Maybe I should get a room. |
J. Peter Jordan, FCSI, CCS, AIA, LEED AP (Unregistered Guest)
Unregistered guest
| | Posted on Monday, May 07, 2012 - 08:48 pm: | |
Mediocre products installed by good roofers will usually outperform great products installed by crappy roofers. |
Paul Gerber
Senior Member
Username: paulgerber
Post Number: 102
Registered: 04-2010
| | Posted on Monday, May 07, 2012 - 10:49 pm: | |
Ken, I think you need to check your "Christian" units to metric conversion LOL... 16mm =5/8" and 19mm=3/4"!!!! Those membranes would be gypsum board and plywood thicknesses!!
60mil = 0.060" * 25.4mm/in = 1.524mm
80mil = 0.080 * 25.4mm/in = 2.032mm
Conversions compliments of your favourite "token Canadian" spec writer
Ride it like you stole it!!! |
Paul Gerber
Senior Member
Username: paulgerber
Post Number: 104
Registered: 04-2010
| | Posted on Monday, May 07, 2012 - 11:14 pm: | |
Alan, I'm with you on mod bit vs BUR!! IKO, Firestone and Bakor also have good mod bit membranes. The modified formulations hold up much better than the traditional asphalt formulations and are much more forgiving in our more extreme climate. About the only time we will spec BUR is if the client is very...ummmm...frugal and insists on it from a cost standpoint. That said we usually document our reasons for mod bit over BUR (always pays to CYA).
With respect to PVC vs KEE, I am not able to give any coconcrete advice as 95% of our projects have mod bit. I have only spec'd 1-PVC roof and 1 or 2 EPDM roofs (and one was for a small canopy on a pre-eng building) in the last 5 years. I did just finish a job with a PRMA EPDM system! It took me back a couple decades when I first graduated and IRMA systems were popular!
Ride it like you stole it!!! |
ken hercenberg
Senior Member
Username: khercenberg
Post Number: 224
Registered: 12-2006
| | Posted on Tuesday, May 08, 2012 - 09:59 am: | |
woops, left out my decimals. Got too caught up with the Sarnafil product numbers (20 for 2.0; 15 for 1.5). Thanks for catching that Paul.
With a 2-ply mod bit system you probably do have a good 7 mm thickness or so. The hot-rubber systems are 210 mils or a little over 5 mm. The nature of the bituminous systems are that they allow for some amount of self-healing action. The big benefit of mod bit and hot-rubberized asphalt (another way of saying that it's modified) is just that, the modifiers prevent water from reacting with the asphalt, the reason you can't have ponding water on BUR. It's why I don't use asphalt to mop-down mod bit, only modified mopping bitumen.
I need a beer. |
Ellis C. Whitby, PE, CSI, AIA, LEEDŽ AP
Senior Member
Username: ecwhitby
Post Number: 145
Registered: 03-2003
| | Posted on Tuesday, May 08, 2012 - 10:54 am: | |
Only one beer? |
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