Laying Rubber Roof On Existing Rubber Roof?

 
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Old 07-14-2011, 04:57 PM   #1
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Laying Rubber Roof On Existing Rubber Roof?


our existing rubber roof was damaged by fallen tree. damage is only on botton edge of roof. theoreticaly i can lay new sheet of rubber over existing rubber after replacing damaged wood. my question is: are there any concerns about the rubber over rubber idea.
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Old 07-14-2011, 05:53 PM   #2
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Re: Laying Rubber Roof On Existing Rubber Roof?


What method of attachment? I presume fully adhered...

Typically, when going over an existing single ply, the bottom membrane should be sliced before doing the layover.

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Old 07-14-2011, 08:02 PM   #3
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Re: Laying Rubber Roof On Existing Rubber Roof?


First off let us qualify what is a "rubber" roof. Around here if someone other than a commecial roofing contractor says "rubber" they are referring to modified bitumen. Modified bitumen actually is not rubber, although it has been affectionally called that since I got into roofing, and presumeably much longer before that.

EPDM is actually rubber. So what kind of roof do you have?


As for EPDM over EPDM no there are no concerns. We are certified by Genflex, sister company to Firestone. Firestone is one of the biggest manufacturers of EPDM roofing. We were hired by Firestone, due to our certification with Genflex, to repair a leaking roof. The specification provided to us stated that we were to fully adhere EPDM over the existing EPDM after washing. Therefore I must assume it's ok if the manufacturer was telling us to do it


Let's assume your roof is modified bitumen. It could be many kinds, but around here a smooth black modified bitumen is very common. There is a specification to use that smooth black modified bitumen as a mid ply instead of a cap sheet, and then install a granulated cap sheet over the smooth. In this case it is a 20 year spec. So again I'd have to say it's OK to do.


But let's think of a situation where it is not ok to install one roof over another roof. In the first situation we were not replacing the entire roof. Althoguh we could have it was not necessary, and that exceeds the scope of this conversation. Local building code, by me in Chicago, dictates that I not install more than 2 roofing layers. Therefore if I were to install a complete roof replacement I would have to tear off if there were already 2 layers. If there are less than 2 layers or I am simply installing a patch, it appears to be totally acceptable based on the information you have provided.
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Old 07-18-2011, 11:28 AM   #4
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Re: Laying Rubber Roof On Existing Rubber Roof?


If its EPDM condensation can and does happen between the two layers, eventually un gluing them selfs. If you just doing a section you most often can cut out the old and put in the new. The problem would be a back water lap. 6" coverstrip over the seam will work for this. If your doing a whole section you can lay a 1/2 coverboard. Either woodfiber or the ISO and start a new.
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Old 07-18-2011, 03:51 PM   #5
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Re: Laying Rubber Roof On Existing Rubber Roof?


Here we go check out page 2 on this PDF... http://www.versico.com/documents/res...hure-10_10.pdf

For a 10 year roof a fully adhered fleecback single ply is acceptable. I suppose the fleece will absorb any condensation A mechanically attached membrane directly over the existing would quality for a 15 year roof.
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Old 07-19-2011, 11:58 AM   #6
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Re: Laying Rubber Roof On Existing Rubber Roof?


Hahah too funny,

The fleece back is because they are using the dash adhesive, other wise known as oly spot. What they dont tell you is that it would be cheaper to lay a coverboard down and fa then it would to use that outrageously expensive adhesive and get a 15year to boot!
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Old 07-20-2011, 07:28 AM   #7
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Re: Laying Rubber Roof On Existing Rubber Roof?


I use the adhesive quite frequently for the insulation. Haven't used it yet to adhere membrane. I find it raises the sale price on average about $20 per square vs using screws and plates. I did it twice last year and so far once this year. There is a very slight increase in production when using it.

What if putting on a coverboard isn't feasable because it's a concrete deck? You'd still need to use adhesive for the cover board, then FA the membrane with BA. So I believe the idea of using a fleeceback would be preferred in a situation where adhering a cover board is redundant.

Yeah if you have a metal deck, and a MA EPDM you can cut into 10'x10', lay a 1/4" EPS (referrably 1/2" or thicker) and fly with another MA EPDM. That'd be a pretty cheap recover.

There are no one size fits all solutions in low slope. I was trying to makea dummy list, errr I mean price list for one of my repair guys who I am grooming into an estimator. Rather than teach him the short cuts, because it would be a tremendous ammount of work to dummy down low slope roofing, I decided to just teach him the long hard way of estimating jobs which will be more accurate each and every time than using a Dummy list. Point is there are no one size fits all solutions, so it's nice to have different bullet types in your arsenol.

Last edited by Grumpy; 07-20-2011 at 07:34 AM.
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Old 07-20-2011, 11:59 AM   #8
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Re: Laying Rubber Roof On Existing Rubber Roof?


Quote:
Originally Posted by Grumpy View Post
I use the adhesive quite frequently for the insulation. Haven't used it yet to adhere membrane. I find it raises the sale price on average about $20 per square vs using screws and plates. I did it twice last year and so far once this year. There is a very slight increase in production when using it.

What if putting on a coverboard isn't feasable because it's a concrete deck? You'd still need to use adhesive for the cover board, then FA the membrane with BA. So I believe the idea of using a fleeceback would be preferred in a situation where adhering a cover board is redundant.

Yeah if you have a metal deck, and a MA EPDM you can cut into 10'x10', lay a 1/4" EPS (referrably 1/2" or thicker) and fly with another MA EPDM. That'd be a pretty cheap recover.

There are no one size fits all solutions in low slope. I was trying to makea dummy list, errr I mean price list for one of my repair guys who I am grooming into an estimator. Rather than teach him the short cuts, because it would be a tremendous ammount of work to dummy down low slope roofing, I decided to just teach him the long hard way of estimating jobs which will be more accurate each and every time than using a Dummy list. Point is there are no one size fits all solutions, so it's nice to have different bullet types in your arsenol.
We generally shy away from using the adhesive but more and more architects are specing it. The one time I used it while running a job we had a section of the roof blow off after a few months. The adhesive had lost its bond with the concrete. There was still 4x4 iso stuck to the EPDM. Kind of amazing really. Now im not sure if we got a bad batch or what but it really soured my personal taste on it. Plus we dont have the big adhesive rig to do the larger jobs. Heck drilling into concrete is no problem our guys are so use to it, its really rather sad. Although they would rather *HOT* the insulation down but some times that isnt an option either.

I could not have put it a better way my self. Low slope is not one size fits all. Your repair man that your grooming will have a leg up since he knows how the systems work, and what wont work. Ive seen alot of estimators who dont know the first thing about what they are "estimating"
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Old 07-27-2011, 11:06 AM   #9
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Re: Laying Rubber Roof On Existing Rubber Roof?


Hi guys. I was wondering what to do if both end sides of the rubber roof was damaged and you are asked to overlap another ply of rubber? Is it advisable to just put the rubber on the damaged rubber? I wish to know more cause I might someday be in this kind of situation. Many thanks to your future replies
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Old 07-28-2011, 06:22 PM   #10
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Re: Laying Rubber Roof On Existing Rubber Roof?


Always more adviseable to tear off the damaged roof when ever the budget allows. If it's mechanically attached it pretty damned simple and cheap to remove old single ply before installing the new.
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Old 08-09-2011, 02:52 PM   #11
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Re: Laying Rubber Roof On Existing Rubber Roof?


If your are just over lapping 4 - 5" and then mechanically fastnening the new piece., no prob, just don't lay one huge piece over the exsiting EPDM, you will trap water and have migration issues.

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