Garage fire walls where they are required

I hope someone can help me confirm that the plan checkers in lake havasu city, AZ are not making me add a 2 hr fire wall to my RV garage addition costing approx. $20,000 with out cause. The existing structure is a 2 bay garage with a 15’ ceiling height 1530 sq’ and the addition is planned at 2 bays with a 16’ ceiling height 2160 sq’. What they are telling is that since the combined size exceeds 3000 sq’ a fire wall will have to be built splitting the addition to something less than 3000 sq’. I’m an electrical contractor and am not familar with these codes. Any help would be greatly appreciated.

Assuming your AHJ has adopted the IBC and assuming they have classified the garage as Group U occupancy then they are likely correct. Refer to IBC 406.1 for details.