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″ headlap (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″ headlap (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 guage, 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, reference TRI’s Installation Manual Appendix A, MC-05.

Additional Recommendations

Flat profiled roof tiles with a continuous projecting anchor lug, should be installed with a coated underlayment ASTM D4601 or D2626-97b on any pitch. VulcaSeal products should only be installed in fair weather when the membrane, air, and roof temperatures are at 40ºF (5ºC) or higher. These application procedures are presented only as a guideline and are not intended to cover all situations encountered during installation. If special design conditions occur, contractors must comply with local governing code requirements. City and County ordinances could supersede manufacturer’s recommendation and may require a more stringent installation procedure.


The attic space ventilation calculation must be 1/300 ratio of the space being ventilated. A balanced ventilation system maybe necessary to acquire the minimum NFVA (net free vent area) with fifty percent of the exhaust ventilators located in the upper portion of the roof, while the balance of intake ventilators should be located at the eave or at least 3″ above the eave line. Where ceilings are applied directly to the underside of the rafters (cathedral type), cross ventilation for each rafter must be provided.
The Net Free Ventilated Area shall not be less than 1/150 of the area ventilated when there’s no vapor barrier in place.

Exposure Guidelines

VulcaSeal underlayments are not to be left permanently exposed to sunlight. Fontana’s roofing membranes have been developed as a secondary moisture-barrier and are designed to be covered with the final roofing product as soon as possible to prevent the first stage of degradation. The Chart describes Fontana’s Recommended Maximum Exposure periods. Permeability/absorption rates are available upon request.
Staples are not recommended as fasteners.