Building Safety in Ada County, ID (2026)
5 county-level rules, plus city-specific rules for 1 city in Ada County, Idaho.
Verified from official government sources
Fire Sprinkler Requirements
Ada County deletes the 2018 International Residential Code's automatic fire sprinkler mandate for one- and two-family homes outright, so new detached houses and duplexes built in the unincorporated county need no sprinkler system. Townhouses still fall under the sprinkler rule under Ada County Code 7-2-5 unless the builder instead installs two one-hour fire-rated walls, or a shared two-hour wall, between units.
Fire Sprinkler Rules for Homes in Ada County
Light RestrictionsAda County Code 7-2-5 (2018 IRC R313.1, R313.2)
R313.1 Townhouse automatic fire sprinkler systems. Delete the exception in its entirety and replace with the following: Exception: Automatic residential fire sprinkler systems shall not be required in townhouses where either two (2) one (1)-hour fire-resistance-rated walls or a common two (2)-hour fire-resistance rated wall, as specified in item number 2 of section R302.2.2 is installed between...
Childcare Center Rules
Ada County's building code lets a home-based daycare for 12 or fewer children operate as an ordinary single-family home (Group R-3) instead of triggering a commercial day-care occupancy classification. The same 12-child, five-person threshold covers custodial and medical care given inside a dwelling. Cross the headcount and the building has to meet full International Building Code day-care standards instead.
Ada County Building Code Rules for Home Daycare
Some RestrictionsAda County Code 7-2-4 (IBC section 305.2.3, 308.2.4)
305.2.3 Twelve (12) or fewer children in a dwelling unit. A facility such as the above within a dwelling unit and having twelve (12) or fewer children receiving such day care shall be classified as a Group R-3 occupancy or shall comply with the International Residential Code. ... 308.2.4 Five (5) or fewer persons receiving custodial care. Delete section 308.2.4 and replace with the following: 3...
Carbon Monoxide Detectors
New homes in unincorporated Ada County with an attached garage or any fuel-fired appliance must have an approved carbon monoxide alarm outside each sleeping area under Ada County Code 7-2-5. The same alarm requirement kicks in on existing homes whenever permitted work occurs, and every unit must meet UL 2034 and be installed per the manufacturer's instructions.
Carbon Monoxide Alarm Rules in Ada County
Some RestrictionsAda County Code 7-2-5 (2018 IRC M1203.1-M1203.3)
Add a new section M1203.1 as follows: M1203.1 Carbon monoxide alarms. For new construction, an approved carbon monoxide alarm must be installed outside of each separate sleeping area in the immediate vicinity of the bedrooms in dwelling units within which fuel-fired appliances are installed and in dwelling units that have attached garages. Add a new section M1203.2 as follows: M1203.2 Where req...
Building Permits
Any Ada County property owner who wants to build, enlarge, alter, repair, move, demolish or change the occupancy of a building, or add or change a gas or mechanical system, has to apply for and get a permit from the building official first. Small projects like tool sheds under 200 square feet, 6-foot fences and short retaining walls are exempt.
When Ada County Requires a Building Permit
Some RestrictionsAda County Code 7-2-4 (IBC section 105.1)
105.1 Required. Amend subsection as follows: Any owner or owner's authorized agent who intends to construct, enlarge, alter, repair, move, demolish, or change the occupancy of a building or structure, or to erect, install, enlarge, alter, repair, remove, convert or replace any gas or mechanical system, the installation of which is regulated by this code, or to cause any such work to be done, sh...
Building Inspections
A building permit in unincorporated Ada County stays alive for three years from issuance. If the work isn't finished and the final inspection isn't performed and the project approved for occupancy within that three-year window, the permit expires automatically. Restarting after expiration means pulling a brand-new permit under section 7-2-4 of the county code.
Ada County Final Inspection and Permit Expiration
Some RestrictionsAda County Code 7-2-4 (IBC section 105.5)
105.5 Expiration. Add a second paragraph as follows: If work has not been completed, the final inspection performed and the project approved for occupancy or use within three (3) years from the date of such permit being issued, such permit shall expire by limitation and become null and void. Prior to work recommencing after the permit has expired, a new permit shall be obtained. The cost of the...
Building Safety by City in Ada County
1 cities in Ada County have their own building safety rules. Each link goes to that city's dedicated page with code citations.
All Ada County ordinances
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