In Montana, a state building permit is required prior to the start of construction for certain types of new buildings, and/or for alterations, additions, and repairs. Building permits must be issued on all required projects before plumbing, mechanical or electrical permits can be issued and before work authorized under these permits can start.
Montana state law exempts the following from the need to obtain state building permits:
Farm and ranch buildings
Mining buildings on mining property
Petroleum refineries and pulp and paper mills (except office and shop buildings)
Residential buildings containing less than five dwelling units (except when serving transient guests)
Private garages and private storage buildings used for the owner’s own use (not part of a commercial enterprise or business)