Blistering in a new modified bitumen (torch down) roof


#1

Hello All,

In need of a little advice… just spent $13k on a new flat roof (it is a 2 ply modified bitumen smooth (torch down) with aluminum coating) and am concerned about blistering on a 2 month old roof. In some areas the blisters are 3-4 inches wide and 1/4 inch high. The original roofer said not to be concerned… A different roofer just inspected it and said it wasn’t adhered correctly and that blistering “can shorten the service life of a roof, by increasing the membrane’s vulnerability to physical and chemical degradation”.

What does this group say? I have pics:

Thanks in Advance!!


#2

Need pics please.
Ive never seen blisters as you have described on a torch down roof
Mop down? Yes.

Sometimes the material gets too hot in a spot and it looks like a blister.
We cover it with a tar that is appropriate and embed granules.
If that is the case, you dont have anything to worry about.
That is not the spot that will leak in the future when the material starts to breakdown and fail.


#3

Thanks roof_lover! I just uploaded a pic… what do you think?


#4

Is that an STA that’s been coated?


#5

The only info I’ve been given is that it is a 2 ply modified bitumen smooth (torch down) with an aluminum coating. Does that help?


#6

That’s what I thought. I haven’t done torch applied since the 90’s, but I do remember those STA modifieds. This looks like the modified was heated too much and delaminated from the mat. Then it was stepped on with boots to try and push it down. Just asking, what was the reason for doing the coating? Vs. Doing a modified with granules.


#7

We still do torch down modified on a weekly basis, and it defently should not look like that. Was the old roof torn off? It could either be air bubbles that got trapped while they were torching, or if there is another layor of old roofing underneath trapped moisture bewtween the roofs. It shouldn’t leak, but imo a sign for concern or other possible workmanship issues.


#8

I hate to talk down about my fellow roofing laboring brother.
But i am going to have to here.
Ok, those are not blisters Where the surface actually burst
They are wrinkles where it didnt adhere.
A small amount here or there is ok.
Although i scold the technician every time i see one.
It is the seams that are of the utmost importance.
That being said, i really dont expect anyone to get it as perfect as me.
The goal is no wrinkles and a bleed-out at every seam.
But it is not a disaster if that is not accomplished.
All that said, i would retrain the roofer.

So in a nut shell I wouldnt hold back his money
But i wouldnt reccomend his flat roofing either.

Wrong shoes worn,
Must be a flat tread, not one with lugs.
He might even be a little too heavy.
He didnt step back enough from the roll while heating.
Smooth modified does show every imperfection in installation though.
Granulated hides a lot and you can fix it easy.


#9

Too much bleed out on the seams and no bleed out on the laps.

The metal doesn’t appear to be stripped in either.


#10

Yep, didnt strip it in.(sandwich the metal)
Also i think he just used ice and water shield underlayment.
That is why he tells the homeowner “2 ply”
I do that also but i dont tell people it is 2 ply.
Im not positive But he might have Used a brand of underlayment that is not mixing well with the modified.
And Axiom is right about the “laps”.
I call them “side seams”
The “three foot seam”
Not the “33 ft seam”
It is the one that needs the most attention.
And as you can see on the pic, Zero bleed out there.


#11

I’d wager will would find more with more pictures.