Originally Posted by Pjw73nh
Thanks. My outer surface is white. I don't know where I can see the underside of the white. Any suggestions where to look? I also know when I wash it, I get a fair amount of "whitish" color in the water that rinses off. Oxidation maybe?
Go to your bathroom roof vent, pull the 4 screws holding the plastic garnish ring and you'll see the roof membrane cut diagonally (so they could install the vent). It will be stapled to the vent framing. Pull one of the flaps and look at the back. If the flap is white on top/black on bottom, it's EPDM. If it's white all the way through or if it's white with a "flannel/fuzzy backing" it's TPO....
While you're at it, if you're curious about what the roof decking is, you can also see the thickness/material used for the roof decking by pulling that flap "all the way up. The "top layer" that you'll see is the "roof decking".. Typically, it'll be either 1/4" or 3/8" OSB. If it's 3/8", it's considered "walkable" if it's 1/4", it's considered "not walkable" although many people still walk on them "carefully" or when using blocks of Styrofoam or sheets of plywood with carpet to prevent cutting the TPO membrane. The plywood/Styrofoam will spread your body weight over a larger area to prevent "crashing through" ..
I'd suggest, if you go far enough to check the decking thickness, also use a good flashlight and do some "peeking and snooping" in any holes you might see. That will give you some "generalized ideas" on things like insulation thickness, type of air conditioning ductwork, where electrical runs are located, type of roof rafters, and loads of other "frightful things"....