hail damage or manuf defect?

All opinions appreciated…

These are really small pits or identations, probably no wider than 1/8.
Several areas of the roof had these but not all over.

Second two pictures are closeups




Looks like common hail damage to me. (smaller diameter hail) It’s common to see this on parts of a roof. usually all facing the same direction.

Looks like blistering to me

It’s blistering. Hail damage often embeds granules further into the asphalt. blistering sheds granules cleanly and leaves sharp edges

It’s blistering. Blisters leave a clean excavation with steep sides. Hail generally makes a shallower indentation and imbeds granules. Most blistering takes place in the first few years after installation and then stops. Typically due to poor roof ventilation and possibly a sign of low quality shingles. May cause the roof to fail slightly prematurely but functionally, since shingles are two layers thick plus underlayment it’s more of a cosmetic problem than functional damage.

I agree with Kenton.

Is there proper venting installed in this particular roof cavity? Most shingle manufacturers require ridge and soffit vents to qualify for their warranties.

Here’s a closeup shot of the same condition.

Most shingle manufacturers require ridge and soffit vents as another out for honouring their warranty when a customer tries to get compensation.

There was a short piece in the Q&A section of The Journal of Light Construction about 15-18 years ago by Dr. Bill Rose, Researcher in roofing, ventilation, insulation at the U of Illinois. He noted some interesting results of his research that dispels much of the venting banter heard on the street…and here!!

Many shingle MFG. are now offering limited warranties on non vented roof’s.

IKO for one has a limited ten year warranty in their Iron Clad warranty

Put yourself in their shoes…Would you warranty roofing shingles if you find blistered roofing shingles installed on a roof with gable end venting?

I wouldn’t, so I’d note it in my warranty.

Gee!! I wonder what the shingle manufacturers know that they don’t tell the average guy. For years, roofs were unvented, then had to be vented and now back to no venting…Why would they quite abruptly change course and start offering warranties on unvented roofs?

A lot. There’s a lot of proprietary information that they will not discuss. They are very secretive.

Try finding specifics on the asphalt mix designs used in comp shingles.

Try to find a credible study on UV deterioration rates of comp shingle asphalt exposed by hail hits.

Looks like installers placed a removed shingle that had been nailed before to the roof.
Also might be caused by installers and a tool,pitch fork or something else to remove the old shingles and was placed down on shingles with force.
They placed it wrong’’ Shingle’’ tore it off carefully and placed it on top of another shingle.
Thats my take and yes I have seen it done many times and yes I left those roofers that night.
Look at the shingle closely. Its in new shape to me and to new to have blisters and the granular is in top shape. Even in the rain notches between the teeth of the shingles, the granular is still there and lots of it…
Underneth the hole I see the selfseal is that right Kenton…


The venting requirements have changed over the years due to today’s tighter homes. The older homes were not insulated to today’s standards which made the older homes self ventilated due to missing or inadequate insulation. Air would flow right through the walls and ceilings and the attic would not heat up as much due to the looseness of the house.

Today’s homes are insulted to an R-39 (in my area) which makes the attic cavity tight and very hot in the summer months, which in turn causes the attic cavity to become an oven, which in turn can melt asphalt shingles and cause them to blister.

As homes became tighter, shingle manufacturer’s have revised their installation requirements.

Kenton disregard my last statement if a big area was damaged.
In Quebec there are regulations and any building material that would degrade within the first few years or before the warranter is up would be scrutinized extremely well and taken off the market pretty fast.
I thought it might be only that one or two Pitts.
Was there a big area of that type of pitting on the roof.

which in turn causes the attic cavity to become an oven, *which in turn can melt asphalt shingles and cause them to blister.
Dave, can you post some recent case studies that show this to be true?

All attics become an over in the summer months.
Having adequate venting reduces that problem.
That being said.
All homes are not alike. Even if the residential buildings looks similar and built the same year, it might be different in quality of building materials , building practices and so on.
By having insulation at R39 (a standard) set by your area or zone how does that increase the tempter in the Attic.
If the attic is a enclosed space ( air tight) there are pro’s and con’s if the builder did not at tear to strict rules form the manufacture.

Good point… you can’t really make blanket statements that cover every condition because conditions… building codes, materials and installations… have changed so much over the years that inspectors in different parts of North America can easily read something that might be true for materials installed in one part of North America, but might be completely untrue for their part of North America.

I don’t have case studies, this is my actual experience with inspecting thousands of Massachusetts & New Hampshire roofs with venting issues.

I’ve seen many roofs under 10 years old (with improper venting) that need to be re-roofed immediately. Simply climbing into thousands of hot 140+ degree attics in the summer months can tell you a lot about attic ventilation. Simply put excessive heat to tar and see what happens…It melts.

Dave, I’m not challenging your experience but I do think the melted shingle is a bit extreme. I would love to see some photo’s of these roof’s you inspected.

My point is that when you make a blanket statement about MFG. warranties you may do a disservice to you client.

First of all, I have been roofing, siding and working on building envelopes for 25 years and inspecting for 15. I have never seen a shingle MFG. warranty their shingles on an individual basis. The only time I ever see them honor a claim is when it’s a wide spread problem in the same geological location, similar to what happened to Bird several years ago.

Back to ventilation. I’m not saying not to do it but in today’s world of construction there are many options and we as inspector should know all the science behind ventilation. As Brian said, for years homes where built with no ventilation, later these home’s where retrofitted and no ventilation added. All I’m saying is there is arguments both ways.

For example, the home I have lived in for the last 21 years and has no ventilation. I replaced the roof many years ago and it’s ageing as it should.

Bottom line is I never mention MFG. warranties in any of my reports and as I said in my earlier post most MFG. like IKO for example are offering limited warranty’s for non vented roof’s.

There have been studies that have confirmed that roof deck and shingle temperature do not change significantly because of venting or the lack of it.

Here is a good article on the subject.


I should also add that in all my years doing this kind of work I rarely seen ventilation and insulation installed correctly, hence the reason the shingle MFG. won’t honor the warranty.