Boise, ID Zoning Overlays & Bonuses: Density Bonus Law (2026)
Key Facts
- Governing section
- BCC § 11-04-05.6
- Applies to
- Foothills Planning Area, Hillside Overlay
- Bonus range
- 0.5 to 4.0 units/acre
- Min open space parcel
- 1 acre, 30-ft avg width
- Approval body
- Planning and Zoning Commission
Summary
Boise grants extra dwelling units in the Foothills Planning Area when developers set aside open space, using a sliding formula table.
In return for the preservation of open space, applicants shall be permitted to develop additional dwelling units beyond those permitted in the existing base zoning district(s) pursuant to the formula in Table 11-04.6 .
(b) These provisions do not increase the area of the site that may be developed, but increase the number of units that may be developed within the same buildable area. Additional dwelling units may be added to the density base units without the requirement for additional open space preservation.
(c) The number of additional dwelling units permitted is based upon the ratio of (i) buildable area to be preserved as open space to (ii) the buildable area to be developed.
(d) Additional dwelling units are allowed based on the percentage of built area occupied and open space dedicated as shown in Table 11-04.6 : Density Bonus Formula, provided that the formula is unchanged. If the numbers for the applicant's built area fall in between the numbers provided in the left-hand column, the density bonus will be calculated based on built area shown in the table that is closest to, but higher than, the applicant's built area. For example, if the applicants project has a built area equal to 73 percent of the site area, the density bonus will be based on the factors shown for a project with a built area equal to 75 percent.
(e) The density formula may be adjusted to allow density
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: 2026 S-31: Code current through: Ord. 20-26, passed 6-9-2026).
Full Breakdown
Under BCC § 11-04-05.6, developers in Boise's Foothills Planning Area (and the Hillside Development Overlay) can build more units than base zoning allows if they preserve open space. Table 11-04.6 sets the trade-off: dedicating 25% of the site as open space earns a 0.5 unit/acre bonus, while dedicating 75% earns a 4.0 unit/acre bonus (up to 100 bonus units per 100 acres). The open space must be at least one acre, average 30 feet wide, and have less than 25% slope to qualify, unless the Planning and Zoning Commission classifies it as priority open space (wetlands, riparian areas, wildlife corridors, etc.).
Violations & Fines
Density bonus units require Planning and Zoning Commission review of the open-space set-aside and design standards; developments that don't meet the eligible open-space criteria are capped at base zoning density with no bonus.
Frequently Asked Questions
How much extra density can a Foothills project get in Boise?
What open space counts toward Boise's density bonus?
Sources & Official References
Other rules in Boise
Compare Boise to another location·View the Idaho zoning overlays & bonuses overview
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