ADU Contractor in Boise, Idaho
Idaho registered ADU contractor specializing in backyard cottages, in-law suites, and garage conversions for Boise homeowners
Boise's residential landscape is one of the most diverse in the Treasure Valley — from 1910s Craftsman bungalows in the North End to 1970s ranch homes on the Bench to modern custom builds in Southeast Boise. That diversity means ADU construction in Boise requires a contractor who understands not just how to build, but how to navigate the specific challenges of each neighborhood: aging utility infrastructure in historic areas, strict North End Historic District design review, Boise PDS permit requirements, and R-1 zoning constraints that vary by parcel.
Boise's ADU market has surged as property values have climbed and housing supply has remained tight. A properly designed and permitted ADU on a North End or Southeast Boise property can generate $1,200–$1,800 per month in rental income while adding significant documented value to your home. That return depends entirely on the quality of the build — which is why hiring a licensed, experienced ADU contractor matters so much.
Idaho law requires any contractor performing construction work over $2,000 to hold a valid Registered Contractor Entity (RCE) license. ADU construction involves structural engineering, foundation work, separate utility connections, and permits for every trade. An unlicensed contractor cannot legally pull permits in Boise — and without permits, your ADU is uninsurable, creates title problems when you sell, and may be ordered demolished.
Iron Crest Remodel is a fully registered Boise ADU contractor with deep experience navigating the City of Boise permit process, R-1 zoning requirements, and the unique challenges of building ADUs on both historic and contemporary Boise properties. We handle everything from initial zoning research through final Certificate of Occupancy — so you can focus on the outcome, not the process.
Boise's ADU zoning framework is layered — state law establishes a floor of homeowner rights, and the City of Boise adds its own standards on top. Understanding both is critical before you invest in design or permitting. Here is what governs ADU construction on your Boise property:
Idaho's 2026 ADU Law (Senate Bill 1354)
Under Idaho's 2026 ADU law (Senate Bill 1354, Idaho Code § 67-6541, in force since July 1, 2026), every city over 10,000 residents must allow either one internal or one detached ADU per lot, may not cap an ADU below 1,000 square feet or 75% of the primary home, may not require owner-occupancy, and may require added parking only in limited cases (such as lots within a quarter mile of transit, an employment area, or commercial services). ADU setbacks may be no stricter than those for a single-family home in the same zone, and qualifying projects are approved administratively. Cities have until February 1, 2027 to update their codes, and historic districts are exempt.
Boise R-1 Zone ADU Standards
In Boise's residential zones an ADU has no setback of its own — it meets the dimensional standards of the underlying zoning district (§ 11-03-03.2.B(6)): 5 feet at the interior side and 15 feet at the rear in R-1C, 10 feet and 20 feet in R-1A and R-1B. A detached accessory structure of 121–500 square feet kept under 14 feet in height may use reduced setbacks of 3 feet at the side and 9 feet at the rear (Table 11-04.4). State law separately bars ADU setbacks stricter than those for a single-family home in the same zone. Boise's current Modern Zoning Code (§ 11-03-03.2B) still reads 900 square feet or 70% of the primary structure's total floor area, whichever is smaller, with no more than two bedrooms and one ADU per lot, and no owner-occupancy requirement and only limited parking requirements; the city must raise the cap to at least 1,000 square feet or 75% by February 1, 2027, so confirm the limit in effect with Planning & Development Services. Lot coverage and height limits vary by zone. North End lots average 6,000–9,000 square feet — many are large enough for a detached cottage when sited correctly. Iron Crest performs a full parcel analysis to identify your ADU envelope before finalizing any design.
North End Historic District Requirements
Properties in Boise's North End Historic District face additional design review requirements through the Historic Preservation Commission. New ADU construction must be compatible with neighborhood character in terms of materials, massing, roofline, and siting. Historic districts are exempt from the 2026 state ADU law, so Boise's existing ADU standards and HPC review continue to apply there. This adds review time and design constraints but does not prevent ADU construction on qualifying lots. Iron Crest designs historic-district-compliant ADUs that maximize livability within these guidelines.
Permit Authority
City of Boise Planning and Development Services. ADU permits include building, electrical, plumbing, and mechanical applications. Iron Crest Remodel manages the entire permit process — application, plan review responses, inspection scheduling, and final Certificate of Occupancy.
Boise ADU costs reflect both the type of unit and the specific demands of the neighborhood. North End properties with older utility infrastructure and potential historic district requirements carry higher construction costs than newer Southeast Boise or Bench properties. Here are the typical cost ranges for each ADU type in Boise:
Detached Backyard Cottage
$190,000 – $320,000+
Full foundation, framing, roofing, utility connections, and interior finish. Most popular on North End and Southeast Boise lots. Historic district properties may be at the higher end of this range.
Attached In-Law Suite Addition
$130,000 – $210,000
Addition to the existing home with private entrance, full kitchen, bath, and living area. Shares some utility connections with the primary dwelling, which reduces infrastructure costs.
Garage Conversion ADU
$85,000 – $150,000
Most cost-effective option. Converts existing garage — including many North End alley-accessed garages — to fully permitted living space with insulation, HVAC, plumbing, and finish work.
All cost ranges include design, permitting, construction, and utility connection fees. Iron Crest provides a detailed line-item estimate with a fixed-price scope and no vague allowances. You know exactly what you are paying for before you sign anything, and any owner-requested changes or unforeseen conditions requiring additional work are documented and approved before additional work proceeds.
Iron Crest Remodel follows a structured, transparent process on every Boise ADU project. Here is exactly what happens from your first call to the day you hand your new tenant the keys:
Property Assessment and Feasibility
We visit your Boise property to evaluate lot dimensions, setbacks, utility access points, soil conditions, and existing structures. We confirm ADU feasibility under current Boise R-1 zoning and identify whether your property is in the North End Historic District. This consultation is free with no obligation.
Design and Engineering
We develop full architectural plans and coordinate structural engineering for your ADU. For North End Historic District properties, we design for compatibility with the neighborhood's character — appropriate materials, proportions, and rooflines that will pass design review while delivering a highly livable and rentable unit.
Permitting and Historic Review
We submit the complete permit package to City of Boise PDS, including building, electrical, plumbing, and mechanical applications. If your property is in the Historic District, we coordinate the design review submission concurrently. We respond to all plan review comments and track every permit through to approval.
Site Work and Foundation
For detached cottages, we manage all excavation, grading, and foundation work. Utility trenches for water, sewer, and electrical are installed in coordination with the foundation schedule. In older Boise neighborhoods, we carefully evaluate existing sewer lateral and electrical service capacity before construction begins.
Framing, Systems, and Finish Work
Framing, windows, insulation, electrical, plumbing, HVAC, drywall, flooring, cabinetry, countertops, fixtures, and exterior finish are all managed by Iron Crest's own crews under a single dedicated project manager. Roofing is coordinated with a licensed roofing contractor as part of the overall project. Every trade inspection is scheduled and passed before the next phase begins.
Final Inspection and Certificate of Occupancy
We schedule the final City of Boise inspection, address all punch-list items, and obtain your Certificate of Occupancy — the document that legally authorizes your ADU to be occupied and rented. We walk through the completed ADU with you before considering the project closed.
When you hire Iron Crest Remodel as your Boise ADU contractor, you are working with a fully registered, insured, and locally experienced builder. Here is exactly what backs every ADU project we deliver:
Iron Crest does not operate as a lead-generation service that sells your project to the lowest bidder. We pair an in-house project manager on every Boise ADU we build. From the day we break ground to the day you receive your Certificate of Occupancy, the same team is accountable for your project.
The following government agencies, industry organizations, and official resources provide additional information relevant to your remodeling project.
See Your Remodel Before You Build.
Upload a few photos of your kitchen, bathroom, flooring, or exterior and get AI-generated concept visuals tailored to your space, style, and materials — free, no obligation, in about five minutes. Then request a real estimate from our Idaho registered Boise team.
Free concept preview · No credit card · Licensed Idaho contractor
How do I hire a licensed ADU contractor in Boise, Idaho?
Any Idaho contractor performing work over $2,000 must carry a valid Registered Contractor Entity (RCE) license issued by the Idaho Division of Occupational and Professional Licenses. ADU construction in Boise involves structural work, plumbing, electrical, and mechanical systems — all requiring licensed professionals and city-issued permits. You can verify a contractor's RCE status on the DOPL website. Iron Crest Remodel is fully registered (RCE #6681702), insured, and has built ADUs throughout Boise's diverse neighborhoods from the North End to Southeast Boise.
How much does an ADU cost to build in Boise, Idaho?
ADU construction costs in Boise typically range from $90,000 to $320,000+ depending on type, size, location, and finish level. Garage conversions are the most affordable option at $85,000–$150,000. Attached in-law suite additions run $130,000–$210,000. Detached backyard cottages — the most popular choice in Boise's North End and Southeast neighborhoods — typically range from $190,000–$320,000+. Historic North End properties may add 10–20% to costs due to utility infrastructure age and potential historic district review requirements. Iron Crest provides a detailed, line-item estimate before any work begins.
Does Boise allow ADUs on R-1 zoned lots?
Yes. Boise's R-1 (single-family residential) zones permit ADUs on qualifying lots under both City of Boise zoning ordinances and Idaho's 2026 ADU law (Senate Bill 1354). Boise's current Modern Zoning Code allows one ADU per lot — attached, detached, or as a garage conversion — capped at 900 square feet or 70% of the primary structure with no more than two bedrooms, and does not require owner-occupancy or added parking (outside the Harris Ranch Specific Plan, which still requires owner-occupancy and one added parking space until Boise conforms to state law). By February 1, 2027 the city must raise that cap to the state floor of 1,000 square feet or 75% of the primary home and allow either one internal or one detached ADU per lot, so confirm the limit in effect with Planning & Development Services. North End lots, which tend to be 6,000–9,000 sq ft, are frequently large enough for a detached backyard cottage. Iron Crest conducts a full parcel zoning analysis before any design begins.
What are the permit requirements for ADU construction in Boise?
Boise ADU projects require permits through City of Boise Planning and Development Services (PDS). You will need a building permit plus separate sub-permits for electrical, plumbing, and mechanical work. Plans must be drawn to Idaho Building Code standards, and a full plan review is required before any permit is issued. The North End Historic District may require an additional design review for any exterior modifications visible from the street. Iron Crest manages every permit application, responds to plan review comments, and coordinates all inspections — you do not have to navigate this process on your own.
Are there historic district restrictions for ADUs in Boise's North End?
Yes. Properties within Boise's North End Historic District face additional design review requirements for exterior modifications, including new ADU construction. The Historic Preservation Commission evaluates proposed ADUs for compatibility with neighborhood character — materials, roofline, window proportions, and siting all factor into the review. Iron Crest has experience designing ADUs that satisfy historic district standards while still maximizing livability and rental appeal. We build the design review package into our permitting process so there are no surprises.
What types of ADUs work best on Boise North End lots?
Boise's North End lots — typically 6,000–9,500 square feet — are well-suited for detached backyard cottages and alley-loaded garage conversions with ADUs above. Many North End properties have existing detached garages accessed from the alley, making a garage conversion or garage-with-ADU-above project a practical and historic-district-friendly choice. Attached in-law suites work on properties with sufficient rear or side yard. Iron Crest evaluates your specific North End parcel to identify which ADU type maximizes your yield while meeting all setback and lot coverage requirements.
How much rental income can I earn from a Boise ADU?
Boise ADU rental income typically ranges from $1,200–$1,800 per month for a well-constructed, properly permitted one-bedroom unit, and $1,600–$2,200 per month for a two-bedroom unit. North End and Southeast Boise ADUs command the highest rents due to walkability, proximity to downtown, and BSU. At $1,500/month, a Boise ADU generates $18,000/year in gross income — a strong return on the construction investment. Short-term rental income can be higher but is subject to Boise's short-term rental regulations. Iron Crest builds ADUs with rental-optimized layouts and durable finishes designed to attract quality long-term tenants.
How long does ADU construction take in Boise?
ADU projects in Boise typically take 5–9 months from initial consultation to Certificate of Occupancy. The timeline includes 4–8 weeks for design and engineering, 4–8 weeks for City of Boise permit review (allow extra time for historic district properties), and 3–6 months for construction depending on ADU type. Detached cottages take longer than garage conversions due to foundation and utility work. Boise's PDS permit timelines have improved with online tracking, but complex or historic district projects can extend the review phase. Iron Crest provides a realistic timeline during your consultation and communicates proactively throughout every phase.
Costs and permit requirements differ by jurisdiction across the Treasure Valley. These guides cover Boise specifically.
Talk to a real project manager
Have Questions? Call Now for a Free In-Home Consultation.
Mon–Fri 7 AM–6 PM · Idaho registered & insured · No obligation
Russ Shloma — Project Manager
Russ Shloma — Project Manager
Hire a trusted ADU contractor in Boise
Get a free, no-obligation estimate for your Boise ADU project. Registered, insured, and backed by our 3-year workmanship warranty.
Get Your Free Estimate