Bitumen roof "disintegrates" in rain?


We just bought a townhouse with a flat modified bitumen roof. Soon after our purchase, the HOA had a roofing contractor patch up the roof. I noticed today that the scupper box was overflowing, so I had my husband try to figure out what was clogging it. He couldn’t unclog the downspout, but he removed a bit of the material clogging the gutter, and it was the roofing material. Furthermore, when he would touch the roof, the roofing material would disintegrate like wet sand. Is this normal? What should we do?

I’d appreciate your input. thank you! :slight_smile:

Is this normal? What should we do?

No. It’s not normal. You should have it looked at, in person, by a pro.


What do you mean by “wet sand”?

Can he push his finger into the roofing material?

Or does it feel like sand?

If he can push his finger in. This may just be the kind of material used. Such as coal tar.

If it feels like sand, this may just be an accumilation of debris near the scupper box.

If the roof desinigates when you touch it. Your house would be full of water.

Hi Lefty,

I forwarded my husband your questions, and this is how he replied:
It’s a collection of tiny gravel-like granules, possibly bound together with a certain amount of mud. It’s of the consistency whereby one could make a small sand castle, and there is a lot of it! I’ve seen similar material in dry form laying loose on the roof, but never in quantities like this. It is light gray colored, and looks to be like the material that is covering (and is stuck to) the rest of the roof.

Maybe he means that the stuff that is disintegrating is the roof membrane material?

I will try to post pics later.

Here is a pic of the scupper box and the area of the roof with the “disintegration”:

Here is a pic of the material clogging up the downspout. Do you think we could use a wet/dry vac to get it out?

thanks for your help! :slight_smile:

its probably dirt build up along with granuals.
exspecially if your pokin it back by the scupper.
unclogg your scupper and quit pokin your roof.


All roofs have some loose granules specially when they are brand new this is normal .

The top picture seems to be a small low-spot before the scupper which holds some dirt and this loose granules .

This does not mean your roof is disintegrating .

However debris like this will cause your roof membrane to deteriorate (rot) prematurely.So just try to keep it clean as regular maintenance and you should be fine .

As far as the debris removed from the downspout its gravel so this will make me believe there used to be a gravel roof before on your home and they removed it and installed the torch down , and they forgot to clean out the scuppers .

Again is mainly maintenace work of keeping things clean . Just stick something down the downspout and push that out and run some water in it .

Its mainly dirt and rock .

Just my opinion …

This is very common on any flat roof no alarm .

that is decomposing organic material and loose granules. aka poop, guess you didn’t sniff it.

no worrys clean it twice a year.


The roofers should have cleaned out the downspout.

Your roof is normal. This will gather at the scupper exspecially with a reroof. They could have removed the old roof at the scupper. Then the water would flow out easier and faster. Thus no dirt and gravel buildup.

Nothing to worry about.

Gweedo for the win… :mrgreen: