Does Flashing Cement Every *get hard*

Pre Final prep before HVAC guys come back to put the mechanicals back on.

Just curious. It’s been about 2 1/2 weeks since the roof was finished, Where they put flashing cement (vent stacks, roof hatch, etc), while it’s skinned over, it’s still quite soft. Just curious, does this stuff eventually dry and get hard, or does the oils in just evaporate and it’s very mushy ?

I suppose in 4-5 years, it will get hard just due to the sun and elements beating on it ?

If it’s exposed to the sun it will harden and crack eventually, how long depends on which brand and how it’s applied.

If it is good quality plastic cement/tar and sandwiched between something away from the sun it could remain pliable and sticky for 20+ yrs depending on the brand.

Def Exposed to the Sun. I’m no roofer and I just short of googling, but doesn’t urethane like product exist for area’s as such (vent pipes, metal-roof membrane like my roof hatch, etc. AKA, good 2 part urethanes for concrete-sealing has been a game changer for me - Vulkem, Sonneborn, etc. Takes the stretch and doesn’t crack, etc. Granted, what in the roofing world exists that plays well with metal-asphalt the best. Currently has regular 19 on it. Whole it’s still soft, should I scrape it off and put 19 Ultra ???

Roofer put a coat of 169 after he finished our 3 layers roof - (2 layers of smooth 160, and then tri-ply rubber as the base). I just finished putting a coat of 298 on the wall where where HVAC is going back on, as once it’s installed, I will never be able to reach behind this area ever.

Once the HVAC shop is done, and the systems is confirmed working fine, I plan to use up the remainder of the 298 on the rest of the roof.

Yes urethane would be more subtitle for exposure to the elements.

Any specific ~urethane~ sealants that adhere to both the contraction/expansion of the asphalt/metal - recommendations ?

Thread Bump. 2nd coat of alumin 298 is going down next week.
Should I just #19 alone or should I replace it with a better product.

Areas with flashing cement : metal roof hatch, vent stacks, etc.