EPDM Questions

big builder

Hello Everyone,

I am wondering whether I sould tackle an EPDM job on the cottage we are working on.

It is a recovering of an existing EPDM roof. I propose to go right over top of the old membrane with a new one. The existing was covered with a wood deck so it is in pretty good shape.

I am confindent in my skills and abilites to take on new areas of construction.

This being said, I have never done one before.

My questions are this: Can anyone see why it is a bad idea to go over the old roof?

We have cleaned and pressure washed the existing roof, should I now use a chemical cleaner specific for this type of roof?



Thank you for all you advice.

Renegade

Double vapor barrier, big no-no.

You must remove the old, or at least the bulk of the field.

big builder

I agree two vapour barriers are not good.

How is this the case here? I propose to glue another single ply membrane over the existing membrane to essentially make it one roof two layers thick.

The actual vapour barrier, insualtion, sheeting etc will remain from the original roof.

MALCO.New.York

If a 100% complete and total bond with no gaps is achieved, I can see this being feasible. But..........

Lack of a COMPLETE bond could lend itself to air pockets that would expand and contract at a different rate, compromising that particular area.

The other factor is the actual densities of the two different membranes and their inherent expansion/contraction rates. Could spell disaster.

__________________
Something to One may be Nothing to another!

Ultimate Wisdom---------
http://www.youtube.com/watch?v=OW-cnizLDEE

roofpro350

I would recommend that you remove the EPDM, normally we atleast slice the membane every 10 feet and remove the base flashing. Because this is a fully adhered system that would not be an option. You will experience condensation problems if the adhesion between the two membrane fails or is not 100% adhered to eack other. I would cut the membrane and install a roof seperator (insulation) and then install the new membrane. Only if this is the second roof installed. Good Luck

Renegade

I see, you are talking about adhering the new rubber directly to the old. That won't work either, for the reasons stated above. Nothing wrong with re-using the old insulation. Often we've been able to peel the old rubber off with no major damage. You don't absolutely have to remove every stitch of rubber, you just don't want it intact. If that is possible, then just screw down 1/2" 1-sided recovery board and install new rubber. That is very do-able.

Sounds like increasing the height may be an issue for you though. Like we say, "Always something, never nothing" eh?

RooferJim

well there was a case where we glued a new EPDM roof with bonding sdheasive right over the old membrane on a low budget job. Of course we used black glue on the laps. It still looks good 15 years latter. go thin and broom it in good.

big builder

Thanks everyone.

I really appreciate everyones input.

I see that the dynamics are more complicated then I originally thought.

Since last we spoke I call Firestone to talk to their technical people about it.

They indicated that is is possible to do, but you can't use the bonding adhesive since it doesn't work on rubber to rubber. One would have to use splice adhesive for rubber to rubber.

We then discussed a loose lay of the rubber. Since the sleepers are every 16" then they said it was OK since it shouldn't move around too much.

I wanted to leave the original roof their for the extra measure of protection. This deck involves many different parapets, roof vents ( copper) pryamid skylights, copper dripedges etc.

Since the rubber is glued right to alot of the copper it would be a major chore to remove.............and we are talking large quantities of copper here.

I see your point of the expansion and contraction. Would a loose lay help in this situation? Or would it be worse.

Raising the deck height is a bit of a problem, although I could probally fix that when we redo the staricases.

I have to admit , the research is half the fun of learning new skills.

Thanks again for all your efforts

RooferJim

Bonding adheasive does work. Like I said in some cases it can make a good roof and has regardless of what the white collar reps will tell you. bear in mind they always want to sell you more expensive materials.

RoofGod

It doesn't sound like they tried to sell him anything. They suggested loose lay which means no glue at all. If you slice the old epdm every 5' then you can adhere it or loose lay it either way will be ok. And splice adhesive is better but bonding will work to.

big builder

You are correct Roofgod. Firestone was very good, they simply spelled out what would be the product to use given the criteria I laid out.

WHy is it so important to slice the old roof befor adhering the new roof?

My dream of having double protection is slipping away......

Will the fact that the roof will be totally covered with decking help with the expansion and contraction rates? Without the sun on it the temperatures will be significatly less.

I assume using the 60 mil is the way to go?

RoofGod

Slicing the old membrane helps with condensation and more than that with the exp/cont. I have glued directly over without cutting the old and it works but you may have issues later on. I suppose a little condensation between the sheets wont hurt anything and if the deck is sitting on it its not going anywhere. If you clean it good and use splice adhesive I don't think any of these things will be an issue. And yes 60 is better than 45 and 90 is better than 60 when it comes to puncture resistance.

MALCO.New.York

Negates the "Double Vapor Barrier" effect.

__________________
Something to One may be Nothing to another!

Ultimate Wisdom---------
http://www.youtube.com/watch?v=OW-cnizLDEE

BULLHART

Be sure to use a good base tie in detail.

I work for Firestone Technical, and I assure you that they weren't trying to sell anything.

big builder

You mean the RPF strips?

BULLHART

Yep

RooferJim

well Firestone used to have a product that was just for sales hype called S-40 fasterner sealant if my memory serves me correct. Its been quite a few years since we did warranty work so they may not have it anymore. It was this nutty idea that a dab of there speacial caulking would prevent a screw from backing out . Firestone was not alone though Carlisle had a product called inseam sealant wich was a crazy caulking you would put in the laps over the black glue, dont know what the hell that was supposed to do. This was back when the only one that had seam tape was Genflex "they invented it". There where also a lot of crazy systems and details that came and went. like Plate bonded, Carlisle's Mars system, Goodyears grid system to name a few. they used to have us use all uncured on all the walls. boy that was expensive, and a lot of it cracked.

RoofGod

S-40 was not to prevent fastener back out it was to stop the head from wearing through the membrane. In seam sealant was to prevent condensation from entering the rear of the seam and degrading the seam adhesive.
And I don't believe genflex invented anything. They buy there stuff from someone else and are the Guinea pigs for new products.

RooferJim

Roofgod I would make a gentlemens bet to differ. Genflex started with seam tape in the late 1980s before anyone, and it was there thing. Genflex also was the first to put tpo on the market. Like I said I will bet you a lobster dinner. but if you win, you still have to drive to cape cod but I know my roofing and im right .

RoofGod

I believe your right Genflex was the first to market seam tape I'm not sure they invented the stuff though. Dow/Stevens claim to have invented the first reinforced tpo sheets in the late 80's. Genflex claims to have entered the tpo market in 1996.
We can call it a push. Lobster sounded good though.