FAILURE OF ASPHALT SHINGLES. IS
THE WIND TO BLAME?
Asphalt shingles are the most popular choice in
North America for water-shedding roofs. They are relatively inexpensive, easily
applied and durable in all weather conditions. There are two basic types: organic
and fiberglass. Both of these types are available in a variety of styles such
as tab and laminate. Most asphalt
shingles manufactured today have a fiberglass core.
The
majority of the people attribute the cause of damage to asphalt shingles to the
wind force. However, we find that the majority
of roof shingle failures are caused by factors other than the wind.
Many
factors are affecting wind damage to asphalt shingles. They include,
but are not limited to, the age of the shingle, installation errors (high
nailing, poor sealing, etc.), handling/storage errors, premature aging of the
shingle, the design of the shingle, and the quality control of the shingle when
manufactured (sealant failure, etc.).
FEMA’s post-storm assessments during the past fifteen
years have shown asphalt shingle roof systems with six years or more of service
were more than 50 percent likely to incur some form of wind damage than their
newer counterparts. We have also seen
shingles rapidly deteriorating in roofs that are not well ventilated such as
gross gable roofs and cathedral ceiling roofs.
The water condensation in these poorly ventilated roofs led to major
water damage issues that were attributed to the leaking roof and damaged
shingles. Our investigations found otherwise.
Regarding the errors during shingle installation,
the leading cause of shingle damage, we have observed shingle fastening errors,
incorrect fastener placement, poor attachment at the eaves, and so on.
Here is the installation instruction from a leading
asphalt shingle manufacturer:
Fastening
Instructions
Place
fasteners 5/8" above the tab cut-out and below the sealant strip. Fastening into the sealant strip interferes
with sealing and contributes to blow-offs
Use four fasteners in normal wind areas.
Despite these instructions, during
our inspections we found that many times the fastener is placed directly
through the sealant strip as is illustrated in the attached photo. This will interfere with the proper adhesion
of the top shingle tab to the adhesive strip below. Many times we observe high-nailing the
shingles which prevents the seal strips from coming into contact with the
overlying shingle tab, thus preventing it from sealing. It can also interfere with the complete sealing,
resulting in a partial seal. Other times
we observe over-driven or under driven nails.
Many times, the lack of adhesion is evidenced at the edges of the tab,
as this is where the incorrectly-placed fastener interference is the greatest.
Sometimes we find a limited number of shingles on a
roof did not seal because the cellophane strips have attached to the seal
strips instead of staying on the underside of the shingles in the package. That way, the solar heat could not activate
the sealing strip. It is not unusual to
find 15-20 shingles that failed to seal on an average size roof.
Forensic Investigation of
Property Damage Claims
Metropolitan Consulting, Engineering &
Forensics understands your need to complete a claim investigation accurately
and efficiently as possible. Whether it
is accident reconstruction, damage due to environmental forces such as wind,
water, hail, snow, tornado, etc.; fire origin and cause investigation or any
other claim, the engineers at Metropolitan understand both you and your client
want to resolve the claim. The analysis
you receive from Metropolitan will be accurate, complete, timely and cost-effective,
giving you the information needed in the claim adjustment and analysis.
Our services have extended beyond the forensic
analysis phase into the remediation and repair phase of many large loss
claims. Upon the completion of the cause
and origin (C&O) investigation, Metropolitan can provide our clients with
complete working drawings and specifications needed to repair or rebuilt
damaged buildings or other structures.
Metropolitan Consulting & Engineering’ staff possesses many-many
years of experience in rehabilitation design, construction management, and
project oversight to ensure the loss is restored in a timely and cost-effective
manner without sacrificing quality.
Building code knowledge allows us to identify possible code upgrades as
needed. Metropolitan understands
constructability and realizes making an insured whole goes beyond forensic
investigation and design. We pride ourselves in providing practical solutions
contractors can understand and follow.
Metropolitan Engineering, Consulting & Forensics (MECF)
Providing
Competent, Expert and Objective Investigative Engineering and Consulting
Services
P.O. Box 520
Tenafly, NJ 07670-0520
Tel.: (973) 897-8162
Fax: (973) 810-0440
E-mail:
metroforensics@gmail.com
Web pages:
https://sites.google.com/site/metropolitanforensics/
https://sites.google.com/site/metropolitanenvironmental/
https://sites.google.com/site/metroforensics3/
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Metropolitan
appreciates your business.
Feel free to recommend our services to your friends and colleagues.