Asphalt Roof Shingle Wind Damage Causes & Evaluation
     


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Guide to assessing, repairing & preventing wind damage to roofing: this document discusses how to evaluate wind damage to asphalt shingle roofs and tells readers how to identify & explain the most-common failure mechanisms such as improper nailing, failure of shingles to seal. This information is useful when considering how to obtain asphalt roofing shingle failure claims assistance. These defects occur on both organic-mat or fiberglass-mat asphalt roof shingles. Readers are also invited contribute roof failure information to the web author for research purposes. web author for research purposes.

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Causes, Diagnosis, Cure & Prevention of Wind Damage to Roofing

Workmanship and Wind Damage Assessment for Asphalt Shingle Roofs

Wind damaged roof shingles (C) Daniel FriedmanAs stated in Best Practices Guide to Residential Construction:

Most shingles carry a windresistance rating of 60 miles per hour as tested under ASTM 3161 or UL 997, while specialty shingles may be rated to as much as 130 miles per hour. While laboratory tests may not predict actual performance in a storm, a higher rated shingle will likely perform better than a lower rated one.

[Click to enlarge any image]

Shingles rated at over 100 mph are often specialorder items and typically require six rather than the usual four nails per shingle.

Adding two extra nails and extra dabs of plastic roofing cement to a regular shingle can also increase its performance in high-wind conditions (see “Fastening (Nailing) Requirements for Asphalt Shingle Roofs” and “Manual Sealing Requirements for Asphalt Shingle Roofs” ).

A wind-resistance rating is not the same as a warranty. Shingles that carry a wind-resistance warranty generally require that the shingle tabs have been adequately sealed to the adhesive strip and most limit wind coverage to five or ten years from installation.

In cold, cloudy weather or on a steep north-facing slope, manual sealing with roofing cement may be necessary.

Roof Installation Workmanship:

Fasteners/Nailing Problems, Wind Damage appeared to have led wind blow-off of these Atlas shingles, though an investigation of whether or not the shingles had self-sealed was also needed.

Weather: Wind damage can happen to any asphalt shingle roof in severe weather conditions.

However if shingles are not properly nailed, shingles are far more likely to blow off of the roof in even a modest windstorm.

Proper roof shingle nailing is what keeps shingles on the roof in a high wind

Shingle nailing error patterns - FEMA

Roofing product manufacturers are careful to specify where shingle nails should be placed in each shingle and the number of nails required.

In addition to the number of nails, how nails are driven is critial to a shingle's ability to stay on the roof.

Sketch (above/left) of common roof shingle nailing errors is a detail from FEMA's , Asphalt Shingle Roofing for High Wind Regions [2].

How Roof Shingle Nailing Errors Occur

Over-driving nails so that they cut into the shingle or driving nails on an angle so that the edge of the nail cuts into its shingle as well as the next overlapping shingle are examples of common errors.

Below Mr. Skees elaborates on the importance of nailing errors in roof shingle blow-offs. First a little background: How or why does this angled or over-driving of roof shingle nails happen? Roofers depend on speed to make a profit. A roofer moving very fast may use excessive air pressure or nailing gun settings so that s/he can drive nails very rapidly. But improper gun settings over-drive nails, cutting shingles and allowing them to blow off of the roof. And a roofer who reaches out with the nailer (speed again) rather than taking a step is also more likely to drive nails on an angle.

These specifications may vary by shingle type and building location, with more nails specified for high-wind areas such as asphalt shingle roofs applied in coastal areas.


Just How Important is Nailing in Roof Shingle Wind Damage Prevention?

James A. Skees, PE

High Nailing Roof Shingles

When Hurricane Ike turned east after landfall in Texas in September 2008 and tracked up the Ohio River Valley, we had thousands of wind damage claims. I looked at several hundred. All of them I inspected were shingles that were improperly nailed. Most of the missing and torn shingles were nailed above the sealing strips.

Pneumatic Roof Nailer Pressure Settings

Another common nailing issue that leads to unnecessary wind damage is over-driving the nails, most often when pneumatic nailers are used.

Perhaps the most common cause of shingle blow-off in storms is improper or inadequate nailing by the roofing installer.

I don't remember a single wind damage claim where the nails were in the proper location and driven flush with the surface of the shingles. The instructions are usually printed on the packaging, complete with diagrams. In both English and Spanish.

With the compressor set too high, the heads cut through the fabric of the shingle, basically leaving the shingles unattached to the roof.

Another discussion of shingle nailing errors and omissions is at Mr. Skees' comments about LADDERING vs STAIR STEPPING SHINGLES

Follow the Manufacturer's Shingle Nailing & Placement Instructions

Commentary: D Friedman

On a wood shingle failure where all of the shingles were improperly offset the roofer was trying to bluff his way through, insisting that his work was absolutely to spec and correct and in accordance with the manufacturer's instructions. A pile of swept-up debris remained in the courtyard (this was a big expensive roof job).

Taking the roofer aside, away from the client (and from unnecessary embarrassment) I reached into the pile and pulled out one of the inserts from the manufacturer that showed the shingle offset pattern they wanted and the nailing pattern - which was totally different from what he had used. The result was cursing and fist shaking and stomping off the job. The client, however, read and recognized the significance of the manufacturer's instructions.

As Skees points out

The shingle nailing instructions are usually printed on the packaging, complete with diagrams. In both English and Spanish.

Reading the instructions doesn't take but a moment, and it would be a great idea.

Components of roof shingle wind damage resistance

Shingle sealant cellophane strip (C) Daniel FriedmanAsphalt shingle wind resistance combines several factors including

  • the effectiveness of the glue strips on the shingle backs which adhere the shingle courses against wind-uplift (see ASPHALT SHINGLE CELLOPHANE STRIP REMOVAL),
  • extra sealant application in some circumstances,
  • roof pitch,
  • roof orientation with respect to prevailing winds, and importantly,
  • proper shingle nailing patterns.

Not only must nails be properly placed and spaced, improper nailing itself, such as driving a nail through the shingle, leaving a nail sticking up to cut a shingle above, or using a roofing stapler improperly leaving cocked staples or shingle-cutting staples will all encourage shingles to fly away with the wind.

If an new roof has the bad luck to encounter a severe wind storm shortly after asphalt shingles have been installed, it is possible that the shingles will blow off of the roof because their self-sealing tabs have simply not had time (or warm enough weather or enough sun) to adhere.

For FEMA advice on wind damage resistant construction of roofing, see "Asphalt Shingle Roofing for High Wind Regions, Home Builders' Guide to Coastal Construction" [PDF], FEMA 499, August 2005, Technical Fact Sheet No. 20.

Roofing Shingle Glue Strip or Glue Tab Adhesion Failure as Contributor to Wind Damage to Asphalt Shingle Roofs

Adhesive spots on an asphalt roof shingle (C) Daniel Friedman

Our photo (left) shows a typical 3-tab asphalt roof shingle (this one is made by GAF™). The shiny black strips form the "glue line" on the shingle. This adhesive is intended to bond to the three tabs of the next shingles nailed atop of this one when the roof is later warmed by sunlight.

On occasions, particularly during high wind conditions such as hurricanes, defective glue strips or adhesive strips on the underside of asphalt shingles may not provide sufficient adhesion, or if the shingles were not properly handled and the glue strip was dirty, an adhesion failure can lead to failure of the shingle tabs to adhere to the nailed-down header of the shingle above. In this case exposure to high winds can cause shingles to tear or blow off of the roof, increasing the degree of water damage inside the building when such winds are accompanied by rain.

In most climates exposure to even a few weeks of normal sunlight will cause the glue tabs on the under-side of asphalt roof shingles to soften and adhere to the surface below.

We discuss the function of asphalt shingle adhesive strips, handling the protective cellophane strip, and shingle uplift wind damage prevention in more detail below.

Extra Sealant Recommended for Shingle Wind-Damage Resistance

Figure 2-7 Shingle Sealing Details (C) Wiley and Sons, S BlissAs detailed at ASPHALT SHINGLE INSTALLATION stated in the printed text: Best Practices Guide to Residential Construction:

In cold climates, the asphalt shingle sealant strip may not set up properly and may require manual sealing.

For three-tab shingles, place two quarter-size spots of plastic roof cement under the lower corners of each tab (as shown in Figure 2-7).

With laminated shingles, place four to six quarter-sized dots, spaced evenly, about one inch above the bottom of the overlapping shingle.

Our page top photo shows the standard sealant strips found on asphalt shingles, in this case a GAF® product we photographed at a Home Depot® store.

Here is what the GAF Materials Corporation, Grand Timberline™ Premium Architectural Shingle Application Instructions say about the glue strips and cellophane. You'll note that we are to leave the cellophane in place, but if site conditions (high wind) require immediate shingle sealing, an extra step, using additional shingle tab adhesive, is permitted.

WIND RESISTANCE/HAND SEALING: These shingles have a special thermal sealant that firmly bonds the shingles together after application when exposed to sun and warm temperatures.

Shingles installed in fall or winter may not seal until the following Spring. If shingles are damaged by winds before sealing or are not exposed to adequate surface temperatures, or if the self sealant gets dirty, the shingles may never seal. Failure to seal under these circumstances results from the nature of self-sealing shingles and is not a manufacturing defect.

To insure immediate sealing, apply 4 quarter-sized dabs of shingle tab adhesive on the back of the shingle 1" (25mm) and 13" (330mm) in from each side and 1" (25mm) up from bottom of the shingle. Press shingle firmly into the adhesive. For maximum wind resistance along rakes, cement shingles to underlayment and each other in a 4" (102mm) width of asphalt plastic roof cement.

NOTE: Excess tab adhesive can cause blistering of the shingle. [The company is referring to the use of additional roof shingle adhesive, not the factory-applied glue strip. Also see BLISTERS on ASPHALT SHINGLES -- InspectAPedia]. The film strips on the back of each shingle are to prevent sticking together of the shingles while in the bundle and to keep dirt and debris out of the adhesive material so that after installation the adhesive will work. Their removal is NOT required during application.

Should the Cellophane Strip on the Back of Asphalt Shingles be Pulled Off?

Cellophane strip on a shingle back (C) Daniel FriedmanThe success with which asphalt shingles bond together as the glue strip is heated by sun exposure is a factor in protecting roof shingles from wind-damage and blow-off. But the debate about whether or not a protective cellophane strip found atop this glue strip on new asphalt shingles has gone on too long. Do we remove the cellophane or leave it in place?

A detailed article about this question is at ASPHALT SHINGLE CELLOPHANE STRIP REMOVAL. Excerpts are just below.

Our photo (left) shows the cellophane strip found on the back or "down"
side of a typical asphalt roof shingle. This one is a GAF™ product.

No: In answer to a common reader question, not normally: according to roofing manufacturers, it is not required to remove the cellophane strip on the back of roof shingles before they are nailed. Below we quote from a major manufacturer's instructions.

Yes: as we discuss in more detail at ASPHALT SHINGLE CELLOPHANE STRIP REMOVAL, experts familiar with wind damaged roofs (in coastal areas exposed to hurricanes and in other high-wind areas) previously recommended both the removal of the cellophane strip and the installation of double-sticky-sided roofing adhesive mastic tape or roof cement under shingle tabs at the time of asphalt roof shingle installation.

As Cramer reported in 2009 (see "More on the "yes" answer" just below, currently asphalt shingles sold in high wind areas adhere and cannot be pulled apart by wind (nor hand).

Certainly if you wait to remove the cellophane strip until the moment that the shingle is about to be nailed, taking it off will do no harm, and it may speed the adhesion between shingles that is intended to resist wind blow-off of roof shingles. We suspect that few professional roofers will add to their roofing time and cost by taking a step that is not recommended by the product manufacturer. causing also extra foot traffic wear.

Other Examples of Wind Damaged Shingle Roofs

Wind damaged roof shingles (C) Daniel Friedman Wind damaged roof shingles (C) Daniel Friedman

The photographs here include examples of improperly or inadequately-nailed shingles which blew off in modest windstorms of far less than hurricane strength. In the first photograph below, our correspondent has laid-out shingles retrieved after the storm, showing the location and pattern of nail holes in each shingle - clear evidence of just how they were nailed. Our ridge cap shingle loss (above left) is plainly due to wind damage and is discussed in detail at RIDGE & HIP CAP SHINGLES. The shingles falling off of the barn roof (above right) appear due to a combination of wind damage and possibly inadequate nailing.


  • Workmanship: Fasteners/Nailing Problems
    lead to holes or wind blow-off. Roofing manufacturers provide recommendations for the type of shingle fastener (nails are recommended), the type of roofing nail, and the length of roofing nail required.

    Yes, it is proper for roofing nails to penetrate through the roof decking so that the tips of the nails are visible inside. This is particularly important where 1/2" roofing plywood or OSB decking are used (as opposed to thicker roof decking materials).

    Here is a representative example comment on roofing nails from the GAF Materials Corporation Grand Timberline™ Premium Architectural Shingle Application Instructions:


    FASTENERS: Use of nails is recommended. Use only zinc coated steel or aluminum, 10-12 gauge, barbed, deformed or smooth shank roofing nails with heads 3/8" (10mm) to 7/16" (12mm) in diameter. Fasteners should be long enough to penetrate at least 3/4" (19mm) into wood decks or just through the plywood decks. Fasteners must be driven flush with the surface of the shingle. Over driving will damage the shingle. Raised fasteners will interfere with the sealing of the shingles.

    Experts discussing measures to reduce asphalt roof shingle blow-off in coastal or other high-wind areas recommend against using roofing staples to install shingles.


  • Workmanship: Fasteners/Nailing Problems
    lead to holes or wind blow-off.

    Notice that not only has one shingle already fallen or been blown off of the roof, but its neighbors are sliding down.

    Diagnosis from a photograph is questionable but there appears to be a nailing problem here.








  • Workmanship: Installation Pattern Problems:Laddering
    [Photo: Carl Gerosa, New Rochelle, NY.]


    Details are at LADDERING vs STAIR STEPPING SHINGLES






  • Workmanship, condition of roof deck, roof flashing, roofing felt underlayment: Flashing and underlayment problems: Here is a representative example comment on the use of roofing felt underlayment and roof decking condition, from the GAF Materials Corporation Grand Timberline™ Premium Architectural Shingle Application Instructions:

    UNDERLAYMENT: Underlayment beneath shingles has many benefits, including preventing wind driven rain from reaching the interior of the building and preventing sap in some wood decking from reacting with asphalt shingles. Underlayment is also required by many code bodies. Where an underlayment is to be installed, use a breather-type underlayment such as GAF Shingle-Mate® underlayment.

    ROOF DECKS: Wood decks must be well-seasoned, supported, and tightly-constructed with maximum 6" (152mm) wide lumber, having adequate nail-holding capacity and a smooth surface. Plywood decking as recommended by The Engineered Wood Association is acceptable. Where a Class A rating is required over decks less than 15/32" thick, an underlayment is required. Do not fasten shingles directly to insulation or insulated deck unless authorized in writing by GAF. Roof decks and existing surfacing material must be dry prior to application of shingles.

  • Workmanship: Improper materials/roof-slope problems - installing shingles on low-slope roofs, for example.
  • Holes and nail-pops in shingle roofs, mechanically damaged roof shingles.
  • Choice of roofing, shingle type, underlayment, and roof decking materials: In a 2005 article Paul Fisette cited Mitrani who, more than a decade earlier, concluded that in areas of coastal high winds and storms, OSB was an inferior roof decking product to plywood. Opinion among Florida consultants currently is that OSB is fine and performs as well as plywood. -- Cramer (personal communication 4/1/09).

In discussing wind damage to roofing with your insurance adjuster or roofing contractor, be sure to review the details of original and replacement shingle installation as this can give evidence about the underlying cause of roof failure as well as informing you of how to avoid roof shingle blow-off in the future.

For FEMA advice on wind damage resistant construction of roofing, see "Asphalt Shingle Roofing for High Wind Regions, Home Builders' Guide to Coastal Construction", FEMA 499, August 2005, Technical Fact Sheet No. 20.

For clay or concrete tile roofs, see CLAY TILE WIND & SEISMIC CONNECTORS where we describe special connectors used for roofing tiles in high wind, hurricane, and seismic areas. Standard clay tile roof connectors are discussed at CLAY TILE ROOF CONNECTIONS.

 

 

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Frequently Asked Questions (FAQs) about wind damage to shingle roofs: cause, prevention, repair

Question: what's the best repair for shingles loosened but not torn off by a windstorm

We live in Texas and recently had high winds.  We lost some shingles and the rest were flapping in the wind, meaning the seals were broken.    Will these seals "heal" with the heat we have in Texas, or do they need to be replaced? 
- M.T. 4/17/2013  

Reply: check for visible damage, cracks, extreme bends, re-glue good shingles with flashing cement, remove and replace cracked or damaged shingle areas

MT:

In general if the shingle did a lot of flapping I'm afraid it may be cracked, worn, such that the tab may break off - an on-roof inspection would be needed to decide. I'm a little worried that a shingle tab may have been weakened without showing a visible crack, but I figure especially in a warm climate like yours an asphalt shingle tab can tolerate some pretty good bending without becoming cracked. That's not true in colder areas of the country.

I would not rely on the previously-sealed shingles to re-seal themselves properly once they've been lifted by a windstorm. The fact that the shingles were flapping and have broken seals makes me suspect they may not seal reliably again - after all they failed the first time and so are weaker than before.

IF the shingles appear undamaged but not sealed, you should be able to improve their sealing with a dab or two of roof cement beneath each tab.

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