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ROOFING INSPECTION & REPAIR
AMERICAN CEMWOOD ROOFING
BEST ROOFING PRACTICES
BUILT UP ROOFS
CATHEDRAL CEILING VENTILATION
CERTIFICATIONS for ROOFING CONTRACTORS
CHIMNEY FLASHING Mistakes & Leaks
COLD WEATHER ROOF TROUBLE
DECKS, ROOFTOP CONSTRUCTION
EPDM, RUBBER, PVC ROOFING
EXTRACTIVE BLEEDING on SHINGLES
FIRE RETARDANT PLYWOOD
FLASHING on BUILDINGS
FLAT ROOF MOISTURE & CONDENSATION
Green House or Solarium Roof Leaks
HEAT TAPES & CABLES on Roofs for Ice Dams
ICE DAM PREVENTION
MASONITE WOODRUF FIBERBOARD ROOFING
NOISE CONTROL for ROOFS
PLASTIC ROOFING TYPES
PVC, EPDM, RUBBER ROOFING
ROOF ARCHITECTURAL STYLES - PHOTO GUIDE
ROOF CLEANING RECOMMENDATIONS
ROOF COLOR RECOMMENDATIONS
ROOF INSPECTION SAFETY & LIMITS
ROOF LEAK DIAGNOSIS & REPAIR
ROOF NOISE TRANSMISSION
ROOF REPLACEMENT SNAFUs
ROOFING FELT UNDERLAYMENT REQUIREMENTS
ROOFING MATERIALS, Age, Types
SADDLE CONSTRUCTION at CHIMNEYS
SNOW GUARDS & SNOW BRAKES
STANDARDS for ROOFING
STRESS SKIN INSULATED PANELS
TEST LABS - ROOF SHINGLE
TREES & SHRUBS, TRIM OFF BUILDING
TRUSSES, Floor & Roof
UNDERLAYMENT REQUIREMENTS on ROOFS
VENTILATION in BUILDINGS
WALK-ON ROOF SURFACES
WARRANTIES for ROOF SHINGLES
WORKMANSHIP & ROOF DAMAGE
Roofing underlayment - roofing felt requirements: this article series discusses roofing felt: the requirements for use of an underlayment, such as roofing felt, tarpaper, or other underlayment products beneath asphalt shingles and other roofing materials. We also discuss the moisture permeability of roofing underlayments in hot humid climates.
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Our photo (page top) shows felt underlayment in good condition as a worn out roof was being stripped. It looks as if the installer of asphalt roof shingles (still visible at below right but now worn out) may have placed roofing felt on top of a still older wood-shingle roof.
At left is a peel-and-stick mineral surfaced roofing underlayment shown during installation of a metal standing seam roof. Photo courtesy Galow Homes.
Also see these articles about using roofing felt or underlayments:
As stated in Best Practices Guide to Residential Construction:
Our OPINION is that on new asphalt shingle, tile, fiber cement, slate, and many wood roofs, most roofing contractors apply an underlayment membrane of roofing felt ("tar paper"), or fiber-reinforced roofing felt. A special underlayment may be recommended by the manufacturers of specific roofing product and hybrid products.
Our photo (left) shows new felt underlayment in place during an asphalt shingle roof installation in New York.
While the requirement for felt underlayment beneath asphalt roof shingles seems to be a topic of almost timeless argument subject to much arm-waving and little reading of manufacturer's instructions and warranties, various sources recommend or require installation of a felt underlayment over the roof deck before asphalt roof shingles are installed.
Booth & Roberts reported at length on the uses of underlayments on asphalt shingle roofs, citing (quoting):
The authors point out that
NRCA, Building Code, & Manufacturers Recommend or Require Felt Underlayments on Shingle Roofs
Booth & Roberts and other sources also report that underlayment is required or recommended below shingles. [Reference numbers are to references in the cited document.]
Five Best-Practices Reasons for Using Roofing Felt Underlayment
Best Practices Guide to Residential Construction lists five good reasons to install roofing underlayment:
The roof deck should be sound and level before laying the
underlayment. Fifteen-pound or heavier felt underlayment
See ROOFING UNDERLAYMENT BEST PRACTICES for additional details on installing underlayment as leak-resistant flashing, including
Details about the requirements and benefits of roofing underlayments are at these articles:
Underlayment On Standard Slopes where Asphalt Roof Shingles are Installed
As stated in Best Practices Guide to Residential Construction:
Underlayment Application of Asphalt Shingles on Low Slope Roofs
Continuing from from Best Practices Guide to Residential Construction:
Eaves Flashing Recommendations for Asphalt Shingle Roofs
The best defense against ice dams in cold climates is a so-called “cold roof,” consisting of high levels of ceiling insulation separated from the roof surface by a free-flowing vent space (see “Preventing Ice Dams,” page 97 in the printed text Best Practices Guide to Residential Construction).
Adapted/paraphrased with permission from Best Practices Guide to Residential Construction.
Inadequacy of Roofing Felt as a Vapor Barrier for Asphalt Shingles in Hot Humid Climates?
A Building Sciences Corporation report also elaborates the usefulness of placing a vapor barrier on the roof deck below shingles in hot humid climates. BSC points out that: [some paraphrasing -DF]
[OPINION-DF: from exterior roof inspections at all times of day and seasons, we have not observed this time-related morning roof shingle buckling in the Northeastern U.S. nor in Florida, nor the Southwest, though the authors report the phenomenon. It is possible that the authors are not quite correct that daily buckling and relaxing of roof shingles can be ignored on a vented roof as harmless, since certainly the product is expected to remain flat, and flexing daily might reduce its anticipated wear life.]
[OPINION-DF: we argue at ROOF VENTILATION SPECIFICATIONS that un-vented roofs are not a best building method in any climate.]
[QUESTION-DF: we note that the test chamber constructed by BSC was itself in an enclosed, air-conditioned space, and that the underside of the test chamber roof was at least in part exposed to the air conditioning. It seems possible that the reduced humidity and lower temperatures on the "interior-side" of the test roof may have contributed to moisture behaviors that vary from what occurs in the field. Attics and under-roof spaces such as in an un-vented "hot roof" cathedral ceiling are certainly not exposed to cool dry conditioned air. BSC may have addressed this concern but we did not find it in the referenced article.
Frequently Asked Questions (FAQs) about the requirement or codes requiring roof underlayment or felt beneath shingles or other materials
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Technical Reviewers & References
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