Detached ADU · near College of Idaho, Caldwell, ID
A 491 sq ft Kingfisher 1-bedroom on a Caldwell lot a few minutes from the College of Idaho — the largest pre-approved plan that fits the city's 700 sq ft / 1-bedroom cap, built at Essential finish as a durable long-term student rental on Canyon County's lower buy-in.
Sited a detached Kingfisher on a Caldwell residential lot within walking-and-biking range of the College of Idaho
Confirmed the 491 sq ft plan fits under Caldwell's 700 sq ft habitable / one-bedroom cap with margin to spare
Ran the jurisdiction check first — Caldwell city limits, so city water/sewer and city fees, not Canyon County septic/well
Walled-off bedroom plus a separate living room — the layout that holds long-term tenants and the rent ceiling
Separate entrance and separate electrical metering so the unit reads as a real standalone rental
Essential finish throughout — durable LVP, a full kitchen with pantry, a single full bath — spec'd for tenant turnover, not for resale staging
The challenge
Caldwell caps ADUs at 700 sq ft of habitable space with a one-bedroom maximum — stricter than Boise's 900 sq ft rule, and a proposed amendment to 900 sq ft / 2-bedroom was still pending, not adopted, when this build went out. So a two-bedroom plan was off the table. The owner was targeting College of Idaho renters — a tenant pool that wants a real private bedroom but won't pay Boise-level rent, where Caldwell 1BR medians sit around $1,200/month. The unit had to clear the cap, feel like an actual one-bedroom rather than a glorified studio, and pencil at a Caldwell rent.
Our approach
The 491 sq ft Kingfisher is the largest pre-approved plan that fits Caldwell's 700 / 1-bedroom rule, and its walled-off bedroom plus separate living room is exactly what keeps a student or working tenant in place for a full lease instead of one semester. We held the finish at Essential because durability beats showpiece materials in a rental, which kept the build near the bottom of the turnkey range. Being in Canyon County rather than Ada also dropped the buy-in: no ACHD transportation impact fee — roughly $5,803 per dwelling that Meridian and Eagle pay — and lower underlying parcel prices than comparable Boise lots.
The outcome
The build ran a roughly six-month contract-to-keys timeline and came in toward the low end of the turnkey range at Essential finish. Because the project cost tracks Boise per square foot while the parcel and the impact fees cost less in Canyon County, the cap-rate math leans Caldwell's way even with the lower rent. The owner has a true one-bedroom — private bedroom, separate living room, own entrance and meter — pointed at a steady College of Idaho rental pool, and a unit that already fits the rules as they stand today rather than betting on a cap amendment that hasn't passed.
"We wanted something near the college that an actual tenant would stay in, not a studio they'd leave after a year. The Kingfisher fits under Caldwell's size limit, the separate bedroom does the heavy lifting, and the numbers worked on Caldwell rent because the land and fees cost us less out here."
Brett & Hana T.
near College of Idaho, Caldwell
City
Zoning, plans, and local fit for Caldwell ADU builds.
Cost
Real 2026 pricing by plan and finish for this market.
Plan
Boise's pre-approved 491 sq ft one-bedroom — separate bedroom, full kitchen, full living room, ready to permit.
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