Although fire limits define geographic boundaries, it is not a zoning code issue but rather a building code issue because it stipulates required construction types and fire resistance. "Fire limits" is a Chicago-specific term in the updated Chicago Building Code and is a modification of what the IBC calls a "fire district", found in Appendix D.
The IBC uses fire districts (fire limits) as a way for cities to designate a “densely developed portion of a city where limiting the potential spread of fire is a key consideration.” The fire limits are established to increase the fire resistance of downtown Chicago by generally prohibiting the use of less fire-resistive construction types.
In the current Chicago building code, buildings of Type II and Type IV construction are not allowed, with some exceptions (Chicago Municipal Code 13-116). Wood and other combustible veneers are not permitted on buildings within the fire limits, either. There are also restrictions on how much projections can extend from the building.
The updated CBC states that only buildings erected of construction types IA, IB, IIA, IIIA, or IV, are allowed (D102.1). Note that construction types are different between current and updated versions of the Chicago Building Code.
The updated CBC becomes an optional standard on December 1, 2019, and mandatory on August 1, 2020.
However, there are some carried-over exceptions from the current CBC to the updated CBC permitting some buildings and structures, including temporary tents, construction project trailers, detached private garages, fences, and sheds, among others, to be erected of other construction types (D105.1).
Existing buildings can increase in area (either outward, upward, or internally) if the existing and modifications are built with one of the allowed construction types (D103.1).
Like in many situations in building and zoning codes, there are exceptions. Read the full details of fire limits in the current CBC in Chapters 13-116, and in the updated CBC at 14B-36-3604 Appendix D.
The new fire limit boundaries include much of the West Loop and Near South Side. Both of these areas have seen an increase in development. Due to the nature of the type and size of buildings being built in these areas – new residential, office, and mixed-use buildings – it is likely that a majority of proposed new construction would already comply with the requirements of the expanded fire limits. Therefore the increased fire limits will not materially or monetarily have much effect on new, ground up construction.
The expanded fire limits may have a big impact on the adaptive reuse of existing buildings if the existing stock of buildings is not one of the allowed construction types.
Ask MAPS to conduct an existing building conditions assessment of construction types.