According to TRI’s Concrete and Clay Roof Tile Design Criteria Installation Manual for Moderate Climate Regions Table 1A, where roof slopes range from 2-1/2:12 to 4:12. Standard Slopes: 4:12 to 7:12 -Minimum Code Requirements. One layer of rated ASTM D226-97a TypeII or D4869-02 Type IV asphalt saturated #30 felt is required as a minimum underlayment on all tile roof applications. Fontana VulcaSeal #30 is ICBO ES ER-5434 certified and UL approved. Other underlayments may be used as approved by local building officials. The underlayment shall completely cover the entire wood deck while lapping over hips, ridges and through valleys with a 2″ head lap (horizontal) and 6″ side lap (vertical).
Fontana’s Optional Upgrades
Begin at the low point of the roof; install one layer of VulcaSeal coated membrane ASTM D2626-97b or D4601 to cover the entire wood deck at right angles with a minimum of a 4″ head lap (horizontal) and a 6″ side lap (vertical). Secure membrane with plastic cap nails at head lap 18″ on center, and 24” throughout the field. Over 7:12 pitches, nail the head lap 12″ on center and 18″ throughout the field. Fasteners shall be of sufficient length to hold underlayment securely with a minimum No.12 gauge, 3/8″ diameter head (9.5mm) corrosion-resistant nail that is in compliance with code requirements. Adequate additional fastening should be considered in high wind areas. Hammer tacker staples should never be used under tile.
Fontana’s Low Slope Optional Upgrades
Starting at a lower edge of the roof, cover the entire wood deck with VulcaSeal’s coated underlayment ASTM D4601 or D2626-97b, not a saturated membrane. On all slope installations, a counter batten system should be used; reference TRI’s Installation Manual Appendix A, MC-05 –TRI Guide 2010.pdf Acrobat Reader required.
Staples are not recommended as fasteners.