Undesired Ripples in EPDM Roofing

25 May 2023
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United States
I was hoping to get some advice on some EPDM roofing I'm installing. When I lay the membrane, I can't seem to get rid of ripples in it. I've tried sweeping the membrane with a stiff push broom, but the ripples still remain. I don't think the ripples are a huge issue, but I'd like to get rid of them is possible to improve appearance, draining, etc. This will be a mechanically attached roof. I'd consider myself a novice in the field of roofing seeing this is my first roof replacement.

I'm installing Firestone RubberGard EPDM on a low slope roof. The roof is about 2K square feet with parapets on three of the four sides. This is a residential property.
A brief rundown of the project: we removed four or five layers or roofing plus a layer of OSB down to the structural deck. We then cleaned the deck and parapets pretty meticulously and installed roofing felt with cap nails. (I learned afterwards that roofing felt isn't meant for flat roofs and that this felt cannot come into contact with the rubber because of its asphalt content.) We then installed OSB over the felt and over the parapets. We gapped them slightly (3-2/16ths on an inch) and filled any gaps larger than that with spray foam and by covering them with duct tape.

We are now in the process of laying the EPDM. Per Firestone recommendations, we are laying one piece across the deck and then cutting separate pieces for each parapet. The portion on the deck is the piece where we're getting undesired ripples. The idea as I understand it is to fasten the "top" of the membrane down with a batten bar and fasteners, then attach the "bottom" by using tape and primer and placing it between the overlap of the two membranes.
One last note: I've considered both a mechanically attached and a fully adhered system, and I've decided to go with mechanically attached in this case. I realize that fully adhering the membrane would probably improve this problem.

I haven't seen any other posts on this issue, so any advice is greatly appreciated.


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I had some issues with the water-based adhesive, was advised the other type was more forgiving with repositioning.

I had to do mine with help.... glue the deck, helper held the rubber up and i used a big broom to bring it down slowly, without many ripples.
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