Many types of roofing permit the application of a coating for a variety of reasons, such as increasing solar reflectivity, resisting biological growth, improving impact resistance, or increasing roof life. However, ARMA strongly advises against the application of any type of field-applied coating over installed asphalt shingles.
There are many types and formulations of roof coatings, so it is always important to consult the shingle manufacturer before proceeding with any type of coating. Many asphalt shingle manufacturers specifically do not recommend field coating of their shingles. Additionally, state or local building codes may prohibit this practice, as the field-applied coatings may negatively impact the performance characteristics (including the fire classification, algae resistance, impact resistance, etc.) of the roof assembly.
Some of the problems reported after asphalt shingle roofs have been field coated include shrinking of the coating, which may result in unsightly curling and/or cupping of the shingles or loosening of the granule surfacing of the asphalt shingles. In addition, non-permeable roof coatings may create a vapor-retarding layer by sealing the voids around and between the shingles. If this occurs, it may contribute to moisture accumulation within the roofing system.
It has been suggested by some that the use of field-applied coatings over existing asphalt shingles will produce overriding benefits to the homeowner, such as longer roof life, energy-use reduction, or remediation of small roof leaks. There is limited available documentation showing the extent to which the field coating of asphalt shingles provides any of these benefits, but the risks and concerns mentioned above remain very real. Further, many coatings need regular maintenance reapplications to provide a consistent appearance.
In summary, the application of a coating may be detrimental to asphalt shingles. Be sure to:
- Check with the asphalt shingle manufacturer before determining a specific roof
- Check with the local building and zoning department and, if appropriate, your homeowner’s association to determine whether this application is
DISCLAIMER OF LIABILITY: This document was prepared by the Asphalt Roofing Manufacturers Association and is disseminated for informational purposes only. Nothing contained herein is intended to revoke or change the requirements or specifications of the individual roofing material manufacturers or local, state and federal building officials that have jurisdiction in your area. Any question, or inquiry, as to the requirements or specifications of a manufacturer, should be directed to the roofing manufacturer concerned. THE USER IS RESPONSIBLE FOR ASSURING COMPLIANCE WITH ALL APPLICABLE LAWS AND REGULATIONS.
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