Roof Requirements

A building permit (PDF) is required for installing roofing. In order to apply for a building permit you need to either be a licensed state residential contractor or the property owner (PDF). See the Roofing handout (pdf) for more details.

Existing asphalt roofs

New roof coverings shall not be installed without first removing all existing layers of roof coverings if any of the following conditions exist; The existing roof or roof covering is water-soaked or deteriorated to a point where the roof or roof covering is not adequate as a base. The existing roof has two layers or more of any type of roof coverings. Drip cap is required at the eave. The ice and water protection needs to be installed over the top of the drip cap or gutter apron. All rotted or unsound roof sheathing needs to be replaced.


Typically, asphalt shingles will require a minimum of 4 galvanized roofing nails per shingle. Nails shall be of sufficient length to penetrate through the roof sheathing, or a minimum of ¾", whichever is less. Please refer to the manufacturer's installation requirements for exact location and number of fasteners.

Roof pitch

Asphalt roof shingles shall not be used on less than a 2 in 12 pitch. There are special underlayment requirements for roof pitches between 2 in 12 and 4 in 12. Consult manufacturer's installation requirements for specific requirements.


A self adhering polymer modified bitumen sheet shall be installed from the bottom edge of the roof to a height at least 24" past the interior of the exterior wall line. The remainder of the roof shall be covered with a minimum 15 Number asphalt felt, installed shingle fashion, lapped horizontally a minimum of 2" and end joints vertically lapped a minimum of 6".


The total net free ventilating shall not be less than 1 to 150 of the area of the space ventilated except that the total area is permitted to be reduced to 1 to 300, provided at least 50 percent and not more than 80 percent of the required ventilating area is provided by ventilators located in the upper portion of the space to be ventilated at least 3 feet above eave or cornice vents with the balance of the required ventilation provided by eave or cornice vents. If necessary additional roof and soffit vents must be installed to meet the minimum requirements above.

Exhaust Vents

Care should be taken to insure that kitchen and bathroom fan exhaust pipes are connected to the appropriate dampered exhaust roof vent with no openings into the attic that would allow exhaust air back into the attic space. The exhaust vents should be installed on the roof the same as other attic vents and vent pipe flashing.


Flashings are required in the following locations:

  • In Valleys, metal needs to be a minimum of 24" wide, 26 Gage, and corrosion resistant
  • Around all pipe penetrations and vents
  • Around skylights, step flashing required on sides of window
  • Chimneys and kick out flashing where the roof eave does not extend past the side wall

Crickets and Saddles

A cricket or saddle shall be installed on the ridge side of any chimney or penetration more than 30 inches wide as measured perpendicular to the slope. Cricket or saddle coverings shall be sheet metal or of the same material as the roof covering.


An "in progress" inspection is required for the water resistive barrier for siding and ice & water barrier for roofing. The contractor should notify the inspector when this will be ready for inspection. A minimum 24 hour notice is required. The entire building does not need to be exposed as long as the contractor takes pictures of the covered water barriers and has them available at the final inspection. The purpose of the progress inspection is to assure proper installation of the barriers including any flashing details before covering. When roof is completed, please schedule a final inspection with pictures on site to close out the permit.