No.

Can you help me on this with the specific code you would refer to in arguing your point?

AHJ seems to want to classify it as merchant occupancy, which will cause major additional expenses
(Handicap bathrooms, fire alarm etc)

My client will have less than 16 hours a month over 2 days to sell to the public, while my professional opinion is that the MAIN occupancy is a warehouse, the AHJ says he is classifying it as Merchant

Erect a tent outside for his "Warehouse Liquidation Sale".

Mike McCann
MMC Engineering
http://mmcengineering.tripod.com

Question..if you had a business occupany that contained a large meeting room that could hold 100 people, would the occupancy for the entire structure be changed to assembly? No. I'm not sure why they are not classifying the space as S-1 with incidental use of M.

FC12:

Yes, unless the Group A-3 was separated from the remainder of the building per the IBC.

I suggest posting this question to the ICC and see what their response is. You could then use this as evidence to the AHJ that the occupancy doesn't change because of a warehouse sale.