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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 DORMER TYPES - PHOTO GUIDE
ROOF INSPECTION SAFETY & LIMITS
ROOF JOB PROBLEMS, RESOLVING
ROOF LEAK DIAGNOSIS & REPAIR
ROOF NOISE TRANSMISSION
ROOF REPLACEMENT SNAFUs
ROOFING FELT UNDERLAYMENT REQUIREMENTS
ROOFING MATERIALS, Age, Types
ROOFING TILE SHAPES & PROFILES
ROOFING UNDERLAYMENT BEST PRACTICES
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
ZINC METAL ROOFING
Requirements & recommendations for use of underlayment on asphalt shingle roofs & on low slope roofs. This article explains the benefits of and best practices use of roofing felt or other roofing underlayment products beneath asphalt shingles and other roofing materials. We discuss underlayment or felt installation details for standard slope roofs, low slope roofs where shingles will be installed, and low slope roofs in freezing climates.
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Our page top photograph shows 15# roofing felt underlayment being installed in preparation for placing a new roof on an older home in Poughkeepsie, NY. This article includes excerpts or adaptations from BEST ROOFING PRACTICES, adapted from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.
Readers should see our article on roofing underlayment requirements, codes, and specifications found in these articles:
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
Note that building codes or roof product manufacturers also require using roofing felt in many circumstances including to protect the shingle warranty - see ROOFING FELT UNDERLAYMENT REQUIREMENTS for details.
According to Best Practices Guide to Residential Construction:
On roofs with a slope of 4:12 or greater, use a single layer of 15 lb. asphalt-saturated felt, starting at the eaves and lapping upper courses over lower by a minimum of 2 inches.
Vertical joints should lap a minimum of 4 inches and be offset by at least 6 feet in successive rows (see Figure 2-2). On roofs with a slope of 4:12 or greater, use a single layer of minimum No. 15 asphalt-saturated felt, starting at the eaves and lapping upper courses over lower. Run the felt 6 inches over ridges and hips from each direction, and 6 inches up any adjoining walls.
Secure each course along seams and edges with enough corrosion-resistant nails to hold it in place until the roofing is installed. In high-wind areas, apply fasteners a maximum of 36 inches on-center along overlaps.
For best protection against leaks, run felt 6 inches over ridges and hips, from each direction, and 6 inches up any adjoining walls.
Valleys should be lined with a full width of roofing felt (or bituminous membrane) pushed tight into the valley so there is no slack. Side courses of underlayment should run over the valley lining and extend 6 inches past its edge. (see Best Practices Guide to Residential Construction “Valley Flashing” page 59.)
Guide to Eaves Flashing by Roofing Underlayment Installation on Low Slope Roofs in Freezing Climates
Roof Underlayment Requirements for Wood Shingles, Shakes, or Clay Tiles
Frequently Asked Questions (FAQs) about using roofing felt or undelayments
Questions & answers or comments about the requirement for and installation of underlayment on asphalt roof shingles and similar materials. .
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Technical Reviewers & References
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