In the clay & concrete tile installation manual (ICC ES ESR-2015; http://www.monierlifetile.com/technicaltools/pdf/TRI-ModerateClimate-InstallationManual0806.pdf), on page 8 regarding reroofs it states that when reroofing a wood shake/shingle roof with clay or concrete tiles, solid decking is required in accordance with new construction.
I'm a little confused by this because both solid and spaced sheathing is allowed for concrete/clay tiles and for wood shakes/shingles in the 2006 IRC & IBC. Why would it say that solid decking is required when replacing only wood shakes/shinges? Why wouldn't it be required when replacing other types of roofing materials? And why would it be required at all when spaced sheathing is allowed by code?
I'm a little confused by this because both solid and spaced sheathing is allowed for concrete/clay tiles and for wood shakes/shingles in the 2006 IRC & IBC. Why would it say that solid decking is required when replacing only wood shakes/shinges? Why wouldn't it be required when replacing other types of roofing materials? And why would it be required at all when spaced sheathing is allowed by code?