Asphalt shingle blow-off – how does it happen? And what can you do about it?

If you have an asphalt shingle roof, having the shingles blow off in the wind is one of the ways it can fail.  This post explores what this failure looks like, the possible consequences, some of the causes, and how to ensure this doesn’t happen to you.

Shingle blow-off happens with both new and old roofs.  The more common failures happen near the rakes/gables and below the ridge-line.  There are several causes, some relating to the quality of the installation, and some to the quality of the product.

New roof, shingle blow-off

New roof, shingle blow-off
(Click on image to see it full size)

This image shows a recently installed roof (about 2 years old), which already experienced shingle-blow-off.  While the shingles themselves were installed with a certain degree of care in terms of placement, the nailing pattern shows that the installer did not follow the standard practice, and nailed them too high, which shows either that they didn’t care, or were in a hurry and did place the nails in the right places.  In addition, this particular roof is getting winds directly from the lake without any protection, and the roofers did not attempt to increase the wind resistance of the roof by using any of the techniques for high-wind installation.

Shingle Blowoff_MG_8894_v2

New roof with shingle blow-off
(Click on image to see it full size)

This is a new roof, installed in the fall.  In the spring, the roof is already showing wind damage.  It appears that the fall installation resulted in the tar strips not sealing, and although the roof “looks” well installed, it will continue to fail.  To quote the warranty from one shingle manufacturer (BP) ( http://bpcan.com/CMS/Media/32629_53_en-CA_0_WARRANTY_Shingles_Ltd_EAST.pdf ):

“For the Warranty against wind blow-off to take effect, the self-seal adhesive must be subjected to sufficient heat to activate the bond. When the shingles are installed in environmental conditions that will not produce such temperature or in very windy areas, the shingles should be sealed down with spots of asphalt plastic cement as specified in CSA A123.51-M85.  In addition, contamination of the self-sealing adhesive by dust or foreign matter may prevent the sealing strip from achieving  a full thermal seal. Prior to sealing, shingles are more vulnerable to wind damage.”

 The concern about proper sealing of the tar strip is also seen in the warranty language of IKO (another shingle manufacturer): (http://www.iko.com/publication/iko-manufacturing-warranty/wppa_open/):

(i) the Limited Wind Resistance Warranty will only apply if: (a) the Shingles were installed using roofing nails (not staples) in strict accordance with the instructions on the wrapper and (b) for installations in Canada during the fall, winter or in cool weather, the Shingles have been manually sealed at the time of installation, and for installations at all other times in Canada, and at all times in the U.S., the Shingles have been manually sealed at the time of installation, or have had the opportunity to seal down;

 In short, if the installation of the shingles takes place late in the season, then the roofer needs to take extra precautions to ensure that the shingles do NOT lift prior to the roof having enough heat to melt the tar strips, and therefore effect the seal.

Shingle_Blowoff_IMG_0411_v2

Shingle blow-off despite attempt at “sealing”
(Click on image to see it full size)

 In the above example, the roofer obviously considered the possibility of blow-off and dabbed each shingle with some roofing cement.  However, they did not follow the recommended practice, and the roof still ended up with shingle loss. 

Shingle_Blowoff_IMG_1142_v2

Workmanship as a contributing factor to shingle blow-off
(Click on image to see it full size)

 This example shows the effect of poor workmanship.  The nailing pattern is too high, the shingle alignment is poor, the flashing work is certainly lacking, and there any many signs of a hurried installation.  It can be seen that some repairs were attempted. 

Shingle_Blowoff_MG_8769_v2

Shingle blow-off due to loss of shingle flexibility.
(Click on image to see it full size)

As the asphalt shingles age, they become more brittle.  In some products, there is also shrinkage of the felt and some clawing or curling.  In the above case, the shingles did, for the most part, stay flat, but as can be seen on a number of shingles, started to crack horizontally.  If the tar strip is only partly sealed, then this provides very little resistance to wind forces, with the result that the shingles are susceptible to blow off.

Shingle_Blowoff_IMG_1195_v2

Shingle blow-off can lead to deck damage.
(Click on image to see it full size)

In the above example, we can see that the wind blow-off exposed the deck.  This is another example of the roofer apparently cutting corners by not installing any kind of underlayment under the shingles.  If the wind was strong enough to break off the shingles, it is also strong enough to blow rainwater in between the shingles and onto the roofing deck.  If the roofing deck is not protected by underlayment, then this will result in persistent wetting of the deck.  Depending on the type of decking, this persistent wetting may cause delamination of the plywood, or complete loss of structural integrity in OSB, or contribute to rotting of wood.

Decking with no underlayment_IMG_0062_v2

Deck damage due to lack of working underlayment.
(Click on image to see it full size)

This image from inside an attic, shows what happens when there is no underlayment (or poorly installed underlayment).  Water has been seeping into the deck, causing:

  • Delamination of the plywood (as can be seen by the cracking of the wood veneer),
  • Rusting of nails (every nail is rusty)
  • Entry of water into the attic interior, which increased humidity in the attic and supports growth of mold (see the dark marks on both the underside of the wood, and in the insulation,
  • Loss of decking integrity (as can be seen at the movement of the wood at the H-clips).
Damaged Decking_MG_5446_v2

Deck damage due to missing underlayment.
(Click on image to see it full size)

In the above case, the plywood decking lost enough integrity to require complete redecking.  Fortunately, the mold inside the attic was minimal (due to decent ventilation that ended up drying the moisture as it seeped in), so additional measures of removing the insulation were NOT needed.  The cause of the problem was the failure of the roofer to install appropriate underlayment, and to take into account the slope of the roof and the way the roof system worked.

 How do you avoid this kind of damage?

There are two solutions:

  1. Choose installers who take the time to do it right, who are aware of the weaknesses of each type of material they work with, and who provide the proper second (and third) line(s) of defense in anticipation of strong weather events.
  2. Choose products and installation methods that have a proven track record of preventing the kinds of damage seen in these photos.

Elsewhere on this blog (in the articles section), I’ve posted an article on how to get a good quote for your roof.  What is relevant to this section is the degree of care the prospective roofer pays to understanding your actual situation, and to ensure that the resulting quotation addresses all of the needs.  It should be clear that in most of the above cases, work was done in a hurried manner, without consideration of how failure could occur, and without providing for adequate countermeasures to these modes of failure.

The most effective way to avoid having to worry about blow-off, is to use products and installation methods that CAN withstand wind damage, and associated issues such as damage by wind-driven rain.  These products and installation techniques are more expensive than what one would pay for conventional asphalt shingles, but they look expensive only when ignoring the true durability and the true cost of repairing damage caused by poor choices.

If you are tired of worrying whether your roof will protect your home from the next wind storm, give me a call to explore the options that you need to consider.

(c) 2014 Paul Grizenko

Update (January, 2017):  This article has had thousands of views.  If you have some specific questions on any aspect of the discussion above, please use the comment form (next to the post title) to post the question or comment.  All comments are moderated, and will appear after review and approval.

 

What is condensation?

If you listen to some people, you’d think that “condensation” is the satanic miasma that descends upon the undeserving, punishing them for sins committed in prior lives (or capriciously,  for no reason whatsoever).  In the field of roofing, roofers will look upon an afflicted home and suggest various remedies, many of which are no better than burning chicken entrails under a full moon, or uttering incantations banishing the spirits from the crevices in which they took refuge.  It is also quite common for all kinds of building mischief to be blamed on “Condensation” hence informing the suitably-impressed home-owner that they are in the presence of a superior intelligence.

Fiddle-sticks.

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You have OSB as your roof sheathing. Do you cheer or panic?

That depends on what grade the OSB panels are, and whether the right panels were installed.  OSB (which stands for Oriented Strand Board) is a variant of plywood, and is an engineered product, meaning that each type of OSB panel has defined end-use and method of application.  Information on the types of panels and their uses can be found here:  http://www.apawood.org/level_c.cfm?content=pub_osb_libmain

The panels are manufactured in two grades: Exterior and Exposure 1. “Exterior panels have bonds capable of withstanding long-term exposure to weather.”   The Exterior 1 grade “is intended to resist the effects of moisture due to constructions delays or conditions of similar severity”.  Which means that if the OSB panels have been installed as roof sheathing, then a few days exposure to the weather is permissible before the tar paper or other underlayment is installed.

If the roof panels  are Exterior grade, then you have nothing to worry about.  Most of the panels installed as roof sheathing, however,  are Exposure 1 grade,  which means they CANNOT be exposed to long-term moisture.  That is fine, as long as the roof doesn’t leak, or condensation doesn’t happen.  Leaks, when they do happen, generally start gradually, and it may be several years before a leak is detected.  By that time, the OSB has been exposed “long-term” to weather (which in this context, means water), and therefore the glue holding the wood chips (strands)  together starts to dissolve.  This leads to the weakening of the panel, as well as causing it to swell and buckle with absorbed moisture.  Persistent condensation will do the same.

In short, if you have Exterior grade OSB, you can change your roof when it’s due – the panels should not be affected.  If you have Exposure 1 grade, then you should carry out a regular program of attic inspection to ensure that no water is getting in.  Otherwise, the cost to reroof may have to include the cost to redeck the roof, and do whatever mold remediation that is necessary.

OSB damaged by persistent leakage, being removed.  Note the dark stains in the insulation.  It too will be removed.

OSB damaged by persistent leakage, being removed. Note the dark stains in the insulation. It too will be removed.

From another installation / repair, we had very localized leakage, but it ended up ruining that piece of OSB.

Damaged OSB.  Leakage was localized but still need to be redone.

Damaged OSB. Leakage was localized but still need to be redone.

If you’re not sure of what you have, or if you know you have OSB but aren’t use what state it is in, give us a call.  We’ll do an inspection and tell you our opinion.

(c) 2013 Paul Grizenko