Any of these systems would be a fine choice. Any reason you couldn't use 1/8" or 1/4" tapered insulation to give it some slope? It will add some cost but will help with drainage.
What did you plan on installing the membrane on before?
EPDM as mentioned before is probably the most DIY friendly, but as with any low slope membrane if not installed correctly things can get bad, and bad real fast. And when they go bad they get real expensive.
WW......
Thanks for the reply. Yes, I will be attempting to do this work myself. While I have done a couple of little DIY-esc roof repairs previously, I have no experience with membrane-type roofing such as EPDM/PVC/TPO. That being the case, perhaps ease of installation should play a significant role in my selection of material?
Incidentally, I live in San Diego County. This may also be a factor; I am being told that EPDM is not very popular in my neck of the woods due to local environmental restrictions on selling the VOC-based adhesives which often accompany EPDM.....?
DO your self and pocket book a favor, do a whole lot of video watching and look at the manufactures details before even starting. This may be one of the things that would be best to have a professional do. I'll get in to that later.
They make water based and solvent based Low VOC adhesives for this reason. Or you can mechanically attach any of the systems. I'm not a huge fan of mechanically attached membranes except one system with TPO/PVC. But it's not DIY friendly, at least the equipment to do them are not.
what are the dimensions of the roof? I feel one big advantage of an EPDM over a Modified Bitumen is the ability to greatly reduce seams. But I don't know how big a piece on guy can handle. I have never worked with EPDM but have done a fair amount of SBS. That stuff is pretty easy for one guy in part because the rolls are only 40" wide. But it also means more seams.
An experienced guy can put down a lot of EPDM in a short amount of time. It's lighter then SBS by more then half. but of course no one is laying down 39.75" wide rolls of EPDM either, the costs would become way to high with all the seam tape. And EPDM is not as durable is SBS.
Thanks....I guess I need to do a little more investigation as to the implications of EPDM under the allowed materials / adhesives / solvents in California.
Low VOC/Water Based adhesives, down side is they are about 2X as expensive as standard Bonding adhesive.
The roof is about 28' length x 14.5' in width.
This size could be done in one piece, it would be fairly heavy at around 180 Lbs, depending on access I may split it down the middle. Is this addition a walk out deck by chance?
Have any pictures?
So going in to why some times its better to have a professional do stuff like this is for a couple of reasons.
1. With single ply membranes there is little to no redundancy. By that I mean if the top layer has an issue, that's it, it will leak, where as a Mod bit it may not. Inside and outside corners can be difficult to do. If you happen to mess up the install, it will either need to be patched or completely redone, and that gets expensive.
2. The cost can get pretty expensive, say you have 50' of edge metal you need to strip in, the 6" coverstrip comes in rolls of 100'. What will you do with the extras left over, all of the materials have some kind of shelf life. Where hiring someone you may not have to eat that extra cost. When I break down a job I go down to 1/2 or 1/4 a roll on things like tapes.
There is lots of things to consider while I'm all for DIY projects, some just make sense to have someone else do.
Post a few pictures or drawing of what you are dealing with, some roofs are easier then others.