130
ADU permits issued in Boise in 2024
More than double the 2019–2023 average of 61 permits per year — the largest single-year volume on record for the city's ADU program.
Source: City of Boise ↗
Market Data · 2026 Edition
The 2026 Boise ADU Market Report
Published: May 23, 2026 · Updated annually
Boise issued 130 ADU permits in 2024 — more than double the five-year average of 61. After the December 2023 zoning rewrite, applications jumped nine-fold from roughly 3 per month to 27 per month, opening the largest ADU buildout window in the city's history.
Built in partnership with Iron Crest Remodel, the licensed Idaho contractor (license RCE-6681702) backing the BoiseADU build queue.
The headline figures
Four numbers that define the 2026 Boise ADU market
Permit volume is up. The cap is bigger. The owner-occupancy rule is gone. Rents have held. Together those four facts explain why Boise is the most permissive ADU market in the Mountain West going into 2026.
9×
Permit surge after the Dec 2023 zoning rewrite
Applications climbed from roughly 3 per month in the year before the Modern Zoning Code to about 27 per month within 12 weeks of the effective date.
Source: BoiseDev, April 2024 ↗900
Square-foot maximum ADU size
Raised from 700 sq ft under the December 2023 Modern Zoning Code. The cap is 900 sq ft or 50% of the primary dwelling's living area, whichever is smaller.
Source: BoiseDev / Hawley Troxell ↗$1,479–$1,503
Median 1-bedroom rent in Boise
Two of the three major rent indexes converge inside a $24 band — the reference number for ADU pro-formas underwriting a 1BR turnkey unit.
Source: Apartment List + RentCafe ↗The 2023 zoning rewrite
What the Modern Zoning Code actually changed
Boise's Modern Zoning Code (MZC) passed on June 15, 2023 and took effect December 1, 2023. For accessory dwelling units, three rule changes did the heavy lifting — and together they explain the post-rewrite permit surge.
Maximum ADU size raised from 700 → 900 sq ft
The cap is the lesser of 900 sq ft or 50% of the primary dwelling's living area, with a 2-bedroom maximum. The 200 sq ft of additional envelope is what makes a real 2-bedroom plan (the Kestrel) viable on most Boise lots.
Source ↗Owner-occupancy requirement removed
Before the rewrite, an owner had to live in either the primary home or the ADU. After Dec 1, 2023, an investor can purchase a property with an ADU and rent both units — primary plus ADU — as two separate income streams.
Source ↗Extra off-street parking requirement removed
One off-street parking space had been required for each new ADU. The rewrite eliminated that mandate citywide, opening up narrow lots and corner lots that previously couldn't fit a code-compliant ADU plus the extra stall.
Source ↗City of Boise
"ADUs support the city's vision for thoughtful infill growth and for creating a variety of housing options for our residents."
— Maureen Brewer, Director, Boise Planning & Development Services. City of Boise press release, March 2026.
Permit volume
ADU permits issued in Boise: baseline vs. post-rewrite
The chart compares the 2019–2023 baseline against the two completed years under the Modern Zoning Code and the annualized monthly run rate measured in the first quarter of 2024. The 27-per-month figure is BoiseDev's measured application rate from a 3.5-month window — not a full-year permit count.
Note: 2020, 2021, 2022, and 2023 individual-year counts are not publicly broken out — the city release reports only the 2019–2023 average (61/year). The post-rewrite run-rate bar annualizes BoiseDev's measured 27-per-month application volume from the first quarter of 2024 and is not directly comparable to issued-permit totals.
Pre-approved plan program
Boise's pre-approved ADU plan catalog
On March 17, 2026, the City of Boise released a catalog of eight pre-approved ADU plans designed by Parke Architecture (Eamonn Parke, AIA). Six are downloadable today; two mirrored variants are queued as "Coming Soon." The program targets the ~$10,000 in custom architectural fees that price ADUs out of reach for many infill lots, and is positioned to compress permit cycles from roughly 7–12 weeks to 3–5 weeks for builds that stick to the published set.
| Plan | Type | Size | Status |
|---|---|---|---|
| The Goldfinch | Studio (Type A) | 280 sq ft | Downloadable |
| The Waxwing | Studio (Type B) | 396 sq ft | Downloadable |
| The Kingfisher | 1 Bedroom (Type C) | 491 sq ft | Downloadable |
| The Kestrel | 2 Bedroom (Type D) | 695 sq ft | Downloadable |
| The Sandpiper | Dwelling + Garage (G-1) | 396 sq ft | Downloadable |
| The Osprey | Studio + Garage (G-2) | 376 sq ft | Downloadable |
| The Sandpiper B (mirrored) | Dwelling + Garage (G-1) | 396 sq ft | Coming Soon |
| The Osprey B (mirrored) | Studio + Garage (G-2) | 376 sq ft | Coming Soon |
For full plans, pricing by finish level, and the comparison grid against custom design, see the floor plans hub and the pre-approved program page. Aggregate stats from 6 downloadable plans currently in the BoiseADU catalog mirror the city's set.
Rent market
Boise rent by bedroom count — cross-source view
Two of the three major Boise rent indexes agree within $24 on the 1-bedroom median that underwrites most ADU pro-formas. They disagree most on 3BR — where unit mix and building size skew the averages — but ADUs cap at 2 bedrooms, so the 3BR line is context, not a planning number.
Gap: zip-level breakouts for 83702, 83703, 83704, 83705, 83709, 83712, 83713, 83714, and 83716 are not in this pass — only 83706 returned a clean zip-level series. The next refresh adds the missing nine. Sources: Apartment List, RentCafe, Zillow Rental Manager.
Financing climate
Idaho ADU financing rates — May 2026 snapshot
Three financing paths cover roughly 90% of Boise ADU builds. Rates below are point-in-time captures and re-verify often — every figure is dated May 24, 2026.
| Product | Rate | Lender | Notes |
|---|---|---|---|
| HELOC (variable) | 6.250% | Idaho Central Credit Union | Lowest publicly listed Idaho HELOC at time of capture. Source ↗ |
| Construction loan | 6.750% / 7.088% APR | Mountain America Credit Union | One of the few Idaho lenders publishing a construction-specific rate. Source ↗ |
| 30-yr fixed cash-out refi | ~7.0–7.2% | Idaho average (Bankrate baseline + cash-out premium) | Bankrate 30-yr refi is 6.69%; cash-out typically prices 25–50 bps higher. Source ↗ |
For the full path comparison, HELOC vs construction loan vs cash-out refi, and the underwriting friction on each, see the financing guide. Multigenerational households comparing an ADU build against Boise assisted living costs ($3,125–$4,488/month per ElderLife Financial) usually find payback at year 4–5.
Methodology
How this report was built
Every numeric claim on this page traces back to a public, primary source — the City of Boise, established local outlets (BoiseDev, KTVB), national rent indexes (Apartment List, RentCafe, Zillow), and Idaho lender rate sheets. Where the underlying data is incomplete, the gap is named, not papered over. The report refreshes annually plus on each material City of Boise data release.
Sources
- ADU permit volume — 2019–2023 average, 2024, 2025City of Boise Planning & Development Services press release (March 2026) ↗
- Post-rewrite monthly application rate (3 → 27/month)BoiseDev (April 2024) sourcing PDS ↗
- Modern Zoning Code text + ADU rule changes (size, owner-occupancy, parking)BoiseDev, Hawley Troxell, Sightline Institute, KTVB cross-confirmation ↗
- Pre-approved plan catalog (8 plans, designer, launch date)City of Boise pre-approved ADU plans hub + ArchPaper ↗
- Boise median rent (Studio / 1BR / 2BR / 3BR)Apartment List (May 2026), RentCafe (April 2026), Zillow Rental Manager (Feb 2026) ↗
- Idaho financing rates (HELOC, construction, mortgage)ICCU, Mountain America Credit Union, Bankrate Idaho ↗
Known data gaps
- Year-by-year 2020/2021/2022/2023 individual permit counts — City of Boise publishes only the 2019–2023 average. Granular years require a public-records request to PDS.
- 9 of 10 target Boise zip codes (83702, 83703, 83704, 83705, 83709, 83712, 83713, 83714, 83716) — only 83706 returned a zip-level rent series in this pass. Next refresh adds the rest.
- Pre-approved plan adoption rate — the city has not yet disclosed how many of the 130 (2024) or 82 (2025) permits used a pre-approved plan vs a custom set.
Update cadence: annually (May refresh) plus on each major City of Boise data release. Last updated 2026-05-23.
Frequently asked
Boise ADU market — frequently asked
How many ADU permits did Boise issue in 2024?
Boise issued 130 ADU permits in 2024, up from a five-year average of 61 between 2019 and 2023. The 2024 figure is the largest single-year volume on record for the city's ADU program and reflects the first full year under the Modern Zoning Code that took effect December 1, 2023. Source: City of Boise Planning & Development Services press release, March 2026.
How big can an ADU be in Boise?
The maximum ADU size in Boise is 900 sq ft or 50% of the primary dwelling's living area, whichever is smaller. ADUs are also capped at two bedrooms. The 900 sq ft figure was raised from 700 sq ft under the Modern Zoning Code that took effect December 1, 2023 — that increase is what made true 2-bedroom plans like the city's Kestrel (695 sq ft) viable.
Is owner-occupancy still required for a Boise ADU?
No. The owner-occupancy requirement was removed under the Modern Zoning Code on December 1, 2023. An investor can now purchase a Boise property with an ADU and rent the primary home as one income stream while renting the ADU as a second. Some third-party blog posts still cite the old rule — they are out of date.
How many pre-approved ADU plans does Boise offer?
The City of Boise's pre-approved ADU plan catalog contains eight plans: the Goldfinch, Waxwing, Kingfisher, Kestrel, Sandpiper, and Osprey, plus two mirrored variants (Sandpiper B and Osprey B) marked Coming Soon. Six are downloadable from the city's website today. All eight were designed by Parke Architecture and released March 17, 2026.
What's the median rent for a 1-bedroom in Boise?
Median 1-bedroom rent in Boise is $1,479 according to Apartment List (May 2026) and $1,503 according to RentCafe/Yardi Matrix (April 2026) — a $24 spread between the two largest national indexes. Zillow Rental Manager pegs the all-bedroom median at $1,523 (February 2026). For ADU pro-formas underwriting a 1BR turnkey unit, $1,479–$1,503 is the safe reference range.
When did Boise's Modern Zoning Code take effect?
Boise's Modern Zoning Code was passed June 15, 2023 and took effect December 1, 2023. For ADUs it raised the maximum size from 700 to 900 sq ft, removed the owner-occupancy requirement, and eliminated the extra off-street parking mandate. Application volume rose roughly nine-fold in the first three months under the new code.
Free Lot Check · 24-Hour Response
The Boise ADU window is open right now.
130 permits in 2024. The cap is 900 sq ft. The owner-occupancy rule is gone. Start with a free lot check — plan fit, lot conditions, and the right financing path for your goals. Or call (208) 297-2036.