Prevailing setbacks apply to areas with developed lots (where some homes burned down, and with some homes still standing) of varying front yard setbacks.  See Information Bulletin P/ZC 2023-015 on how to calculate prevailing setbacks.  

For blocks on the same side of a street where there are no developed lots (homes completely burned down), prevailing setback does not apply and the front yard shall be per the zoning code according to the lot's zone.   

For blocks on the same side of a street where some homes were damaged or destroyed and others were not, prevailing setback standards will apply.