Extra eyes on this flat roof

I very rarely see tpo roofs. Didnt even know it had one untill I showed up, the listing said Metal & Composition. Anything pop out at you? Really appreciate it.



These fasteners should not be pressing up and tenting the material in my opinion. I’ve never seen protruding fasteners heads under what appears to be a TPO, EPDM or PVC type material.

Were you able to determine what the material is?


The fasteners are a bit protruding, but does not seem too bad to me. The fasteners probably mean there’s no insulation under there. The TPO material may or may not be Class A fire rated, in case that’s important in your area.

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Hard to tell if its actually TPO or PVC from a photo but, Im leaning towards a tpo. I see cut edge sealant installed at the cut edges of the field membrane so thats usually a tell and a good sign the installer wasn’t completely aloof.

My main concerns are the Black Exhaust vent and Exhaust Flue.

Some initial thoughts:

-Photo #1 - Exhaust Flue: Those fasteners are protruding a bit more than I would like to see, however, i might mark them as “monitor” and not a material defect (unless of course there’s a obvious tear or discoloration in the cover strip material - can you see it pushing through?).

More concerning, the roof flashing at the flue doesn’t turn up vertically. You can see they used a copious amount of sealant to “seal” the joint between the cover strip material at the flue flange and vertical cone. One the sealant fails, water can enter under the cover strip, find a fastener and enter the structure (theoretically speaking of course).

-Photo #3 the Pipe boot flashing (far right) appears to be improperly installed. Water can collect in the inverted area. Depending on your region there can be risk for fungal/pest and/or freeze/thaw damage. I think i see hose clamps and sealant on those 3 pipes. If yes, thats a “proper” detail for most manufacturers. You might note something like “sealant” should be maintained every 2-3 years or as needed in order to maintain a weather tight condition.

–Photo #4 - Black Exhaust Vent (assuming bathroom exhaust) - I don’t even like them on high slope roofs. I would note it as a risk for leakage; especially in a snow region.

-Looks like 6" or less spacing on the perimeter edge fastening, which is generally speaking good for our area I-90 / I-120 wind up lift. Looks like they trapped air or gas at the fasteners. Not great, not terrible. Just monitor.

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Builder’s “inspector” told me it was TPO.

There is spray foam in the attic, if that’s what you’re referring to.

Thank you all! You are a wealth of knowledge and a boon to your community!

Not what I was referring to. With flat roofs it’s possible to do a great job of insulating by placing 2" or more of solid foam sheet above the roof deck, then a layer of gypsum such as DensDeck® to bring up the fire rating, and finally TPO on top.

The continuous sheets of above deck far outperform attic insulation. The DensDeck® gives it the fire rating. And the TPO, if Class A, completes the exterior fire rating.

The roof will have a slightly cushy feel if you walk on it.


Pic 1, furnace exhaust vent appears to be for sloped roof and not a flat roof. Pic 2, wrinkle at the seam center bottom - seam should be physically checked for proper adhesion; air trapped under it may loosen that seam over time with expansion/contraction from heat of sun. Pic 3 bootjack flashing definitely will pond water, should be repaired especially if in freeze zone. Pic 4, I usually see taller gooseneck/cowl type vents on flat roofs but that one may be ok if flange is wide and 360 degrees around its base (and of course if manufacturer specifies for use on flat roofs). Protruding fasteners will need checked periodically to make sure the membrane stays intact.

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Hi William,

TPO and EPDM are sold in Mill Thickness. So for example, you might see 60 MIL EPDM or TPO.

You can Adhere or Mechanically attached either type of membrane. In a mechanically attached membrane assembly the field sheet should be a reinforced membrane (more specific to EPDM as most TPO field sheets are reinforced).

Over the last 10+ years, more TPO Roofing manufacturers have begun to provide “Pressure Sensitive” cover strips for particular warranty terms.

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Interesting Article. I like to think of it this way…

TPO = Plastic
EPDM = Rubber.

Those contractors love selling Silicone Roof Coating Systems…