Roof substructure

Common roof coverings include membrane roofs made of TPO, EPDM or PVC, as well as built-up bituminous roofs, asphalt, composite or wood shingles, slate, metal and concrete tile. A defective mounting structure can damage the substructure, for example the roof insulation. In the worst case the mounting structure can detach from the roof or the roof can collapse. Causes of this failure include weak anchorage of the mounting structure to the roof and not checking that the roof is strong enough for the added PV load plus O&M activities. Adding PV can raise the risk of roof leaks and damage, because there is more foot traffic and there are more attachments to and through the roof membrane. Ballasted racks need a sacrificial slip sheet between the ballast feet and the membrane. Flashings on membrane roofs must use compatible materials specified by the roof manufacturer. Roof O&M means finding and fixing leaks and maintaining the rack attachments. Roofs under warranty need preventive maintenance every year. Steep roofs need a higher level of fall protection under 29 CFR 1926.500. Mounting structure damage that affects the roof, such as cracking, bending or corrosion, is found by visual inspection.

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• sentence 1: support check: partial - Passage lists TPO/EPDM/PVC membranes, built-up bituminous, asphalt, composite, wood shingles, slate, metal and tile, but doesn't say they are the 'common' coverings (concrete tile only as 'tile'/'Concrete tile is common on Spanish colonial homes').
• sentence 6: support check: partial - O&M scope, annual maintenance for warranted roofs, and 29 CFR 1926.500 for steeper slopes are stated, but 'steep' is specific (greater than 3-4:12 pitch) and not just generically steep; core supported. -->