Bumps on Ridge Cap

Hey Guys-

This is on a house built in 2005. The shingles were fine but the majority of the ridge caps had bumps like they were overheated. They were more prevalent on south and west sides and they were not on the ridge vent shingles. The house had soffit vents all around and a couple of ridge vents. Is this from a manufacture defect or possibly overheating of the attic space? Thanks.


Shingle Blisters…


Thanks for the link Mark. I did a search on the message boards for blistering and picked up some additional information. Seems like there’s different opinions out there on whether they are a defective product issue or simply just cosmetic.

I think the differing option comes from the fact the manufactures don’t want to admit that they are a defect. It’s seems obvious to myself and many others that they are.

I agree Mark, there is no Manufacturer that will admit a defect when they can pass it as an aesthetic feature.
As an installer, I would call it a defect. If my house is fine and the next door neighbor has the same shingle of the same year and looks like that, it is not only an aesthetic thingy, it is a defect compared to mine.

That particular roof above is an architectural series and looks fine. The ridge caps are typically three-tab shingles or shingle caps by the same Manufacturer but manufactured in a different run and time as the field material. So it is possible to get a defective product separate from the main roof shingles. :slight_smile:

First of all I do not see enough vents.Secondly in my opinion it is material defect.I have been roofing for 15 plus years and agree it is material defect and no no no material provider will clam his materials are defective for I have gone head to head with these guys on more than one occasion.:twisted:

Definitely a shingle defect on the caps as the roof shingles next to the caps show no problems or premature deterioration. Our roofs really do not get “overheated” as they are (or should be) designed to withstand the temps expected at the top surfaces (especially where much hotter down south where surfaces temps can be 150+*F).

Venting barely affects the temperature at the outer surfaces which receive the direct sunlight. One study done by Building Science Corp in Florida showed only 2-3F temp rise in shingle surface temps with unvented attics under them. How can a 2-3F shingle temp rise be the cause of shingle failure for a shingle that may operate in a seasonal temperature regime of freezing to 100+*F??

When is an attic overheated?

It has been claimed by some on this board that they have measured attic temps of over 160F in attics down south…and this is with venting! Up here in temperate Nova Scotia, unvented attics will only get in 110-125F range, yet folks claim these attics are overheated and will severely shorten shingle life!!

Before the addition of insulation in attics, there was little deliberate venting of attics. These houses had asphalt shingles and no manufacturers were claiming the unvented attics were ruining their shingles prematurely.

With the addition of insulation to attics, the spaces above the insulation now became cold and if you had a wet/damp house below with no airsealing at the attic level, warm moist air rising from below would condense on the now cold roof boards. Adding ventilation in most cases** would cure the condensation. So ventilation eventually became part of better building practice and codes. Somehow, shingle manufacturers jumped on the bandwagon claiming the ventilation was also needed to save their shingles from overheating.

Dr. Bill Rose (Phd building scientist at U of Illinois) says that manufacturers are hiding behind the venting requirement to save themselves from lawsuits (and there are many if you do a GOOGLE search) due to poor shingle quality. Remember the price of oil 10 years ago was down to $10/barrel…asphalt was cheap. In one month, January, this year, the price of asphalt went up 20-25%…in a period with the least demand for it!!! We have seen many, many pictures of shingles with premature deterioration on this website . SO, we should be putting the blame where due, the manufacturers, and remember that lack of venting is not the main cause of premature shingle failure!!

** About 2 months ago, I consulted to government here on a house in their low income energy retrofit program. It had a severe attic condensation problem in the first winter (08-09) after being blown with cellulose fiber (walls + ceilings)in summer 08. The owner (an older widow and only occupant) consulted with both a roofer and a local code inspector in summer 09. Both told her she needed more attic venting, which she had installed last year.

During this past winter, which was a mild, warmer winter here (March had 2-3 weeks of May temps), she felt the house was colder…and she had a worse attic condensation problem!!!

What happened???

Can take the form of “bubbling” just under the surface of the colored granules. Typical blisters can range from pea-size up to the size of a quarter, or even larger. Some blistering on shingles can be due to things like improper ventilation, etc., but sometimes may be attributed to a manufacturing defect. The problem with blistering on shingles is that when one of them “pops”, the granular material that was protecting the underlying asphalt is now gone. It has been shown that UV (ultraviolet radiation), will tend to degrade and accelerate the aging process. Shingles that have open blisters in which the asphalt becomes visible, are at greater risk of premature failure.



You must have copied that from a shingle manufacturer’s website!!

“Some blistering on shingles can be due to things** like improper ventilation**, etc., but sometimes may be attributed to a manufacturing defect.”

How can they tell which of the above caused the blistering, especially the “ETC”? Is there a specific test or symptom we should be looking for to tell whether it’s ventilation, etc., or a defect? IMHO, just more of the manufacturers trying to give themselves an out when the product fails…“must be the ventilation; we have a great product even when made with inferior materials or maybe even fillers in place of ashalt because asphalt is TOO EXPENSIVE!!”

“Shingles that have open blisters in which the asphalt becomes visible, are at greater risk of premature failure”

IMHO, a shingle that has the amount of blisters as shown in the ridge cap has already failed!! So, they think that extensive blistering is not failure.and shingle failure will be premature only when the blisters burst…has got to be a manufacturer speaking!!!

Nope! just from somebody’s Opinion like mine for what I have seen in the past, that is why I copied it. Forget where it came from.

No doubt in my mind it is a defect, if not, it would happen a lot more in this surrounding area. :slight_smile:

SO…how can we tell if the blistering is “a manufacturing defect” or from “an improperly vented roof”?

Roofing warranties | Print |](http://www.nachi.org/index.php?view=article&catid=51%3Acontractors-corner&id=75%3Aroofing-warranties&tmpl=component&print=1&layout=default&page=&option=com_content&Itemid=44) E-mail Departments - Contractor’s corner “Lifetime” shingles and other common myths


By Doug Kerr
Residential roof warranties can be confusing, and there is some basic information that homeowners need to know – and questions to ask a contractor – before committing to one of the largest renovation expenditures.
Warranties can be complex, as well as misleading. Installing “30-year shingles” on your roof does not necessarily mean your roof will be replaced or even repaired if there is a problem, even if something happens within as little as 10 years.


Once you understand how roofing warranties actually work, you won’t get caught up in a sales pitch about warranties and end up not receiving the coverage you believe you paid for.
There are two parts to the warranty: the materials warranty, which is supplied by the manufacturer, and the labour warranty, which is provided by the installation contractor.
Materials warranty

Most manufacturers only warranty the product, not the installation. This means that if their product does not perform as it is supposed to, and the manufacturer has determined that it was a materials defect and therefore covered by its warranty, it can do one of two things:

  1. Replace the shingles: In this case, the manufacturer will back its truck up to your house and drop off new shingles. It will be up to you to install them. If you have chosen your roofing contractor well, and he is still in business 10 years after your roof was installed and he has given a long labour warranty, you may be able to convince him to come back and install the shingles at no charge to you.
  2. Payout: Some manufacturers’ warranties don’t replace the shingles, but will pay you money instead. This sounds good until you discover that the amount is pro-rated, which means it decreases proportionally over time. The usual procedure is for the manufacturer to pay the full amount for five years and then prorate amounts after that. This means that if your 30-year roof fails in 15 years, the company may pay you 30 per cent of what you originally paid for the shingles. The price it pays out will probably not be adjusted for inflation.
    Even “lifetime warranties” are pro-rated and may not be of much value in 15 to 20 years.
    The last bit of bad news about warranties is that most are “performance-based,” which means the definition is based on whether the shingle stands up and performs the way it is supposed to perform. The majority of manufacturers base their warranties on “water infiltration.” So even if the shingle falls apart, the warranty does not apply. It only applies if there is a manufacturing defect and the roof leaks. This means that if all the granules or other protective coverage washes off your shingles, or if they curl and fade, but no water gets into the home, then you don’t have a valid warranty claim.
    **Labour warranty **

Here are some key questions to ask your roofing contractor.
•Does the contractor automatically give you a labour warranty in writing with the quote?
•How long is the warranty for?
•Does the warranty cover installing new shingles, if there is manufacturing defect?
•Will the contractor come back in eight or 10 years and install new shingles at no cost to you, even if it is the manufacturer’s shingle that breaks down?
If the roofing contractor can’t answer these questions, it’s an indication that he or she probably don’t have a standard warranty policy.
You should, therefore, choose a roofing installation company that provides a labour warranty and choose a company you believe will likely to be in business at least 10 years from now.
Good news

There are excellent roofing contractors and some very good manufacturers’ warranties. Here are some suggestions to help you make the right decision.
•Find out if the manufacturer’s warranty includes installation cost or just the cost of materials.
•Determine if the warranty value is based on the original purchase price or on today’s replacement cost.
•Find out if the materials warranty is performance-based or based only on water infiltration. A performance-based warranty will provide more extensive protection.
Also, keep in mind that if the installers don’t install the roofing materials as per the manufacturer’s specifications, the manufacturer will void the materials warranty. Some sources for reliable roofing contractors include the Better Business Bureau, the Roofing Contractors Association of British Columbia and RenoMark renovators who are members of the Greater Vancouver Home Builders’ Association.
*Doug Kerr is president of Absolute Roof Solutions and president of Kerr Construction Ltd. in Vancouver. He can be reached at *
604-263-0334. www.absoluteroof.ca
From Home Makeover, August 2009

This is IKO’s response to roof shingle blisters.
**[/size][/FONT][FONT=GillSansStd][size=2]As asphalt shingles age, large bubble-like blisters may appear on the surface, some as large as a quarter.
They may be open, exposing the asphalt, or closed. Blisters are more likely to appear when there is
inadequate ventilation, or in areas where tree sap drips onto the shingles. Small “rash” blisters do not
affect the performance of the shingles.


A GREAT article, Marcel! Thanks.

It’s good to see someone telling the TRUTH!

I’d like to see the independent research that produced that statement. None has ever been produced. There is some research by Bill Rose showing side-by-side vented and unvented south-facing cathedral roof cavities with the same shingles installed over them: at 15 or so years, no difference in deterioration was evident!!