[quote=“gregvdd”]Hi there,
I am new here.
I am from Montreal Quebec,apologies then for my bad or unclear english.
I have a 1400sq m. flat roof made of tar and gravel.It’s quite old. But had never leaked.
I am planning to change the roof next year, using TPO or EPDM.
I regularly go on my roof to check for any problems.
Last autumn, I 've patched all the flashings have been sealed and painted. I have also had some gravel here and there where needed.
It has been really hot here in the last days,
I have seen some little bubbles, that are at the surface of the roof, they are detached, mixed with the gravel and of the size of little strawberries, sometimes smaller sometimes bigger…
Is that something I have to be worried about ??
I 'll try to take some photos to show you,
thanks
Greg[/quote]
Seriously, if you have a coal-tar pitch roof and it hasn’t been leaking, why are you thinking of replacing it? I was involved in a tear-off of an old CTP roof in Baltimore, Md. years ago, and underneath the roof system we found the society pages from the late 1920’s. That roof was over 50 years old!
As for the bubbles, as others have pointed out it is normal, especially with extreme heat. What is happening is the CTP has become somewhat viscous and the stone aggregate has started to sink into the flood coat of CTP.
Meanwhile, what you can’t see going on is the migration of inter-ply moppings of CTP starting to migrate out from the built-up membrane. The good news is with CTP unlike asphalt, the CTP itself is viewed as the waterproofing agent, whereas with asphalt it is the sandwich created by the build up of plies and asphalt.
So, once again, if it isn’t leaking, I don’t know that I would f*** with the roof unless you are just dying to spend some money or need a write-off. Do you have any photos? How old is “quite old”?