To clarify the requirements of Chapter 15, Section 1510, 2010 CBC as it applies to certain roofing materials, the following policy should apply. Minimum roof covering of any occupancy shall be Class B or better (City ordinance Sec 14.03.160).
Remove all existing roofing and have sheathing inspected.
Re-roof per Chapter 15, Section 1510, 2010 CBC and City Ordinance Sec 14.03.160
Any roof with ponding shall be pitched to drain, before re-roofing.
Asphalt shingles may be applied on slopes of 2 feet per 12 feet or greater or as per listing. Solid sheathing is required. Double felt laid shingle fashion is required for slopes less than 4 and 12.
Asphalt shingles may be applied over wood shingle roofs. An inspection by a Building Inspector is required to confirm the wood shingles are in a condition to act as solid underlayment.
Asphalt shingles may not be installed over wood shakes or spaced sheathing.
No roofs shall be installed over more than one existing roof.
Exception: Manufacturers installation requirements apply and existing roof framing must be designed to carry total load. (Need structural analysis by California Certified Structural or Civil Engineer) and approval of the Building Official.
WOOD SHINGLES AND SHAKES
All wood roofs shall be Class "B" or better. Installer shall show Inspector a listing by an approved testing agency (i.e. U.L.) slip showing Class "B" or higher rated material was delivered to job site. On-site inspection of material being installed may be substituted. Buildings other than residential may require higher classification. (See Chapter 15, 2010 CBC and City Ordinance 14.03.160)
All roofs laid over an existing roof require metal edging. Three-way metal may be used for Class "C". For a Class "B" roof, only three-way metal shall be accepted.
MANUFACTURED ROOFING MATERIALS
Metal, concrete, clay and other manufactured roofing products shall be listed by ICC. Permittee to provide City with an ICC-ES listed number. (www.icc.es.org)
All tile roofs weighing 6lbs or greater per square shall be engineered by a California Certified Structural or Civil Engineer with details of installation. Engineer must wet stamp and wet sign calculations/details.
Re-roofing requiring structural calculations and/or modifications must have a framing inspection before the sheathing material is applied.
Kirke Warren, C.B.O.