Wednesday, July 26, 2017
FAILURE OF ASPHALT SHINGLES. IS THE WIND TO BLAME?
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:
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
Web pages: https://sites.google.com/site/metropolitanforensics/
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