Having a Brainfreeze on this Roof

What is the proper term fopr this type of roofing. Don’t usually see it on residential I know that. And what about the alligatoring?

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Sorry Dale, the link seems to be bad.



I don’t think that’s what it is Dale. Doesn’t look like poly. Looks like a hot mixture spread out over roof.

Built-Up Roofing?


Ian…that Alligatoring looks like Lightweight Aggregate on the roof surface from here.

Odd they would install it in you’re neck of the woods but it’s common here.

Built-up roof would be my guess.

Shrinkage cracking of the bituminous surface of built-up roofing, or the exposed surface of smooth-surfaced roofing, in which the loss of volatile oils and the oxidation of compounds under solar radiation produces a pattern of deep cracks with the scaly look of an alligator’s hide. It occurs only in unsurfaced bitumen exposed to the weather.


I’m with Marcel on this, it is getting more and more unpopular in my area.

When a light aggregate is added to the top coat, it is also known as “pitch and gravel”.

Yeah, that is what it looks like, without the gravel. What you guys think of the condition?

Looks like it is at the end of its lifespan when it gets the alligatoring effect.
That is usually hot mopped on.
They only last just over 10 years.

Yeah, after looking at it Bob, it does look pretty weathered. Time for a new one, I suppose.


Surface asphalt cracks into large segments. This condition is found on smooth surface asphalt roofs. It is caused by the drying out of the exposed asphalt by the sun. If left unattended, this condition can develop into splits in the roof membrane, which in turn will allow water to enter the roofing system and then the interior of the building.

Modified Bitumen
Asphalt degradation is a growing concern. UV-rays oxidize the surface of the asphalt and produces a chalk-like residue. As plasticizers leach out of the asphalt, a modified bitumen or “mod bit” roof becomes brittle. Cracking and alligatoring inevitably follows, allowing water to penetrate the system causing blisters, and cracks. Seam failure inevitably follows causing leaks.A black modified bitumen roof absorbs a lot of the sun’s heat in the summer. High temperatures and UV-rays accelerate asphalt degradation.

I would have it evaluated by a Licensed Roofing Contractor to see if it has gone beyond salvagable repair and needs to be replaced.
Sometimes the membrane has not cracked due to the alligatoring and can be salvaged by installing a top coat which would extend it’s life to maybe another ten years.


Thanks for the quick help guys.

As a side note I would recommend pricing a tear off and switch to Modified Bituman or EPDM.

Never hurts to get estimates from a good flat roof outfit.

Hey Bob, Do they do a lot of residential roofs in EPDM in your area? Around here it is usuall only found on commercial buildings.

Yeah most flat roofs are modified bitumen.
Lots of tar and gravel left on the older stuff and on commercial too.
Not uncommon to see Rubber However on the newer construction though.
Come to think of it I am seeing more modified bitumen trending recently.
Do they hot mop by you ?or are they into the future with the Good year stuff:)
Please do not say roll roofing:)

Built-up roof with craze cracking of the surface asphalt layer caused by long-term shrinkage.

If Modified Bitumen and BUR without gravel is coated and regularly coated (5 years or so)with a good aluminum coating they will last much longer. Don’t coat immediately but wait a couple weeks to let some of the oils to evaporate. I have seen that ponding water and UV are the enemies of flat roofs. Coating as Marcel said if the membrane is not cracked will prolong its life also.