# risidual asphalt on walls, with new pvc roof



## Grumpy (Oct 29, 2008)

So my recent hicup with the asphalt and pitch scuff marks on the pvc roof got me thinking abotu compatibility issues with a pvc roof. When we are tearing off a pvc roof, we expend alot of time chiping and scraping the old hot from the masonry walls. We do this so there is as little asphalt as possible in contact with the pvc. It's time consuming as a mother effer! 

According to the manufacturer a separation must be used. I'm thinking fleeceback. What are you guys doing if anything? Are you seeing any premature failures as a result of some residual asphalt on the walls? 

Most of my jobs are not tear off single ply and put back single ply. Most of my jobs are 80+ year old buildings where the original roof was likely pitch, and it's not unusual to have up to 5 layers of pitch, asphalt and mod bit. That's our average job, so I am up against this on a regular basis. If I am going to be pushing PVC, as I intend to start doing, I need to some up with some answers.


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## 1985gt (Dec 21, 2010)

Kind of a rock and a hard place there. I don't see why fleece back wouldn't work, and the cost would probably be offset by the labor involved in scraping off all the old asphalt. Another option that won't work in every application but, Tear off old flashings bump down smooth and cover with plywood or densdeck. 

None of the options will really be cost effective.


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## LCG (May 30, 2011)

Grumpy, I feel your pain!

Fleece Back
Dens Deck
4 or 16oz Poly Seperation Sheet

Hilti hammer drills and scraper blades when necessary.

Ugh... This conversation is taking me back to a job this summer. 110 degrees and gooey tar, EVERYWHERE!


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## shazapple (Dec 3, 2010)

We typically cover masonry with plywood to give the membrane something better to stick to (in my case its a 2-ply modbit), then the top of the ply is cut at a 45 degree to provide a smooth transition and the membrane is held to the wall with a term bar.


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## Grumpy (Oct 29, 2008)

Fleeceback seems like most economical and effecient. I don't like securing directly to wood personally so if I were to do that, I'd install some kind of cover board. According to Versico, when I inquired if fleeceback was ok, this is the reply I got...


"FleeceBACK is a viable option or the substrate can be overlaid with Plywood, OSB, Securock, DDP."


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## Grumpy (Oct 29, 2008)

PVC just keeps getting more and more and more expensive.


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## 1985gt (Dec 21, 2010)

Plywood is not so bad to glue directly to. Try it a few times and get over your fear of it. :laughing:


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## Grumpy (Oct 29, 2008)

I have no fear of doing gluing single ply to wood. The first EPDM job we ever did about 10 years ago was to glue directly to plywood. 

Wood rots though, that's why I try to avoid it in my roofing assemblies when I have alternatives.


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## 1985gt (Dec 21, 2010)

Well if you install a roof that doesn't leak... :whistling: :laughing:


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## blackangus (Aug 27, 2012)

A majority of my commercial roofing is single ply layover/minor tearoffs on 80 year old buildings also.

I was never a big fan of the "up and over" look, especially with TPO, (too bright and ugly) and in my area I have to get creative for owners to justify roofs that cost as much as the building is worth.

I'll use a wide pressure treated nailer at the base of a wall and top, and separate with a synthetic roofing felt (4' rolls work over most parapets) and the doing a cap over the wall with sheet metal acting as counter flashing. Felt acts as a back-up if cap ever leaks and gets down the wall, or through the mortar and under my roof.

Every situation is a little different of course.

How much does the fleece back stuff cost? I'm not familiar.


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## Grumpy (Oct 29, 2008)

1985gt said:


> Well if you install a roof that doesn't leak... :whistling: :laughing:


Every roof will leak, eventually. The only difference between a good roof and a bad roofer is how long it takes before the roof leaks. I also have a concern about years of condensation from the inside collecting at the wood members because thermoplastic membranes act like a vapor barrier.


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## Grumpy (Oct 29, 2008)

Angus, most manufacturers wills ell a polypropylene separator for what you are describing. The fleeceback isn't that much more, less than the cost of a cover board and extra labor to install it. Probably the most feasable choice for this scenario.


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## Chandlers Roofing (Sep 25, 2012)

Grumpy we do a lot of IB Roofing here and when we come up against this, if we're not replacing with new plywood, we use GAF's Tiger Paw synthetic underlayment. Works terrific! Now, we also do a lot of GAF shingles and almost exclusively use Tiger Paw as our underlayment, so we tend to have it in inventory and by it in large quantities.

Hope this helps.

Chandler's Roofing - Los Angeles and Orange County Roofs -Rain Gutters - Solar


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