Rocked on roof cosmetic or functional

This is the second time I’ve ever seen a flat membrane style roof so I have very limited knowledge and I am recommending for the evaluation based on my lack of knowledge and based on what I see.

My question is are these rocks cosmetic or are they functional in this little portion?

I don’t know but if that is all stones, that is a lot of weight!


What do you see? What type of materials? How are they performing? Does it look old, worn out damaged?

The answers to these questions will give you a basis for a recommendation vs “I don’t know”

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Ballast (rock) has two main purposes with some added benefits on a roof. Two main purposes are:

  1. Protect the underlying material as in a Built Up Roof.
  2. Weigh down the underlying material as in an EPDM membrane that isn’t secured with fasteners.

If the membrane is fastened correctly it may not need the rock but only further evaluation will provide an answer.

This looks like they are attempting to protect the area around the chimney. Seems odd that it is only there. How thick was the layer of Ballast?

Here are a few pictures of what it should look like with ballast covering the entire roof.

From the photo, I don’t think it is ballasted. It appears to be a tar and gravel mix. Ballast would just roll down. Just my two cents.

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Hard to tell from the photo but your probably correct. It looks like a mixture of crap.


I think maybe someone was in the process of working on the roof and moved the stones out of the way and piled them up by the chimney. See the darker area of the membrane in the bottom left corner of the pic? That looks deteriorated to me. If you zoom in, you can see the alligator cracking there. It is either a different age than the rest of the roof or deteriorated quicker there. Possibly ponds water in that area, which increases the rate of deterioration.

You can also see roller marks from where they applied a roof coating of some type over the membrane. (to the right of the darker area at the bottom, 3 roller marks right next to each other.)

The stones are functional like Tony explained and they also help to block UV from damaging the roof.

cnystul1 you definitely should recommend further evaluation by a licensed roofer for this. I would bet that roof is well past it’s life expectancy and has been coated at least one time, maybe more.

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It doesn’t look like a pile of stones. The roof pitches up to the chimney. Kind of like a 6 sided cricket. You can see the flashing around the chimney. :thinking:


Wonder if it was, as you stated a “4 sided cricket” that had a parge coating that has deteriorated and cracked into rubble over the years. :thinking: DK…

NO, It is not a deteriorating parge coating, it looks like white pebbles, maybe to reflect the sun’s rays?

I took a guess as you did, that’s all.

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It was definitely a tar covering over a membrane. The center is definitely rock and pebbles and moss.

It just seemed really odd that the only place with rock was around that chimney. It was also the only place on the entire roof that is visible from the ground so maybe a cosmetic or maybe a functional I couldn’t decide. However you can tell by the roof the rock has moved during past rainstorms

There is the same white material on the chimney flue. Did you check that out? What is the chimney used for? :thinking:

I told the client i was NOT walking on the rocks, there were to many issues with the membrane and I didn’t want to risk a rock damaging it. The flue from where i stood is cement blocks, it was a wood stove, that was converted to gas and now the gas is removed. There were issues with the interior of the flue that were very evident on the interior of the houses such as cracks in the brick that started in the firebox and extended up past the damper in the flue an seemed to be cracked into the small closet behind the fireplace and the whole flue needs further evaluation and repairs.

The whole house was ROUGH!!!

I’m surprised nobody has mentioned the large brown spot in the front left of the picture that’s from pooling water. Supposedly the roof was just looked at and has many years left, neverminded all the random soft spots i foudn just randomly walked during evaluation.

rschmidt4 I definitely recommended the roof be looked at.

I was up on he roof looking at another chimney and stood up and there was the 75 year old female client, so we got to look at the issues first hand.

TOTALLY surprised me!!!

Smart man, Cory!

Hmmm, I think I did:

That’s not what I meant Scott. I know the rocks aren’t 2’ thick there. The roofers just pushed them over there to look at or work on that valley. But it’s definitely not enough material to cover the entire roof so where did the rest of it go?

Never believe anything a roofer that was hired by a seller tells you. I just had one certify a roof that was missing multiple shingles and leaking in 3 places.

Like I said before it has been coated at least once already which is pretty much a guarantee that it is past life expectancy. Coatings are used to cover up membrane roofs in an attempt to extend the life expectancy, and often are just a bandaid job. They are ineffective once you have alligator cracking because the cracking will continue and crack again right through the coating. Once you have that and multiple soft spots (which would have been useful info in the OP Cory) you should recommend further evaluation, or if it was me, I would probably recommend replacement in this case. But I’m also a licensed contractor with lots of roofing experience and can say that.