Wildland Urban Interface Code FAQ
What are the typical construction requirements associated with WUI?
Roofs and roof edges. CBC 705A.1 / CRC R327.5
A noncombustible (tile or metal) or Class ‘A’ roofing assembly is required in SRA – Very High Fire Hazard Severity Zones. All other areas in Santa Cruz County require a Class ‘B’ minimum roofing assembly, including LRA, SRA-Moderate or SRA-High areas. Where the roof profile allows a space between the roof covering and the roof decking, the spaces shall: be constructed to prevent the intrusion of flames and embers; be fire stopped with approved materials; or have one layer of No. 72 cap sheet installed over the combustible decking. Where provided, valley flashing must be not less than 26-gauge galvanized sheet metal over a 36-inch wide No. 72 ASTM cap sheet.
Exterior Walls/siding. CBC 707A.3 /CRC R327.8
Noncombustible, listed ignition-resistant materials, heavy timber, 5/8″ Type X gypsum sheathing behind exterior covering, exterior portion of 1-hr assembly or log wall construction is allowed. The OSFM website (see link above) lists many types of exterior wall coverings that are approved. Note: Ignition-resistant materials are those tested by a facility recognized by the SFM or ICC-Evaluation Service to have a flame-spread rating not over 25, and comply with accelerated weathering tests.
Eaves and porch ceilings CBC 707A.4, A.6 / CRC 327.7.4. R327.7.6
The exposed roof deck under unenclosed eaves and underside of porch ceilings shall be noncombustible, listed ignition-resistant materials, or 5/8″ Type X gypsum sheathing behind exterior covering. Solid wood rafter tails on the exposed underside of roof eaves having a minimum 2″ nominal dimension may be unprotected.