ADU Construction in Boise, ID

From detached guest houses to garage conversions — we handle zoning research, design, permitting, and full construction of accessory dwelling units.

Build an ADU that adds usable space, flexibility, and long-term property value.

Licensed general contractor with ADU-specific experience in IdahoIn-depth knowledge of local ADU zoning rules across Boise-area jurisdictionsFull architectural design and engineering includedComplete permitting management from application through certificate of occupancy

ADU Construction Overview

An ADU (Accessory Dwelling Unit) is a self-contained living space on the same lot as an existing home. ADUs have become increasingly popular in the Boise area as housing demand has grown, zoning rules have evolved, and homeowners have recognized the financial and lifestyle benefits of adding a separate living unit to their property. ADU types include detached new construction (a standalone building on the lot), garage conversions (converting an existing garage into living space), attached additions (building a unit that shares a wall with the main home), and basement conversions (converting a finished or unfinished basement into a separate unit with its own entrance). Every ADU project requires careful navigation of local zoning rules, setback requirements, utility connections, parking requirements, and building code compliance. The design must balance livability, code compliance, construction cost, and long-term value. A well-built ADU adds $100,000+ in property value while generating $800-1,500+ per month in rental income in the Boise market.

Who adu builder is for in Boise

Boise homeowners pursue adu construction for a variety of reasons. Here are the most common situations we see:

✓Homeowners who want rental income from a detached or attached unit on their property
✓Families who need a guest house, in-law suite, or multigenerational living space
✓Remote workers or creatives who want a separate studio, office, or workshop space
✓Property investors who want to increase property value and utility with an ADU
✓Homeowners who want housing flexibility — rent now, use for family later, or vice versa

ADU Construction options in Boise

Not every adu builder project is the same. Here are the most common project types we complete in Boise:

Detached ADU (New Construction)

A standalone structure built on your property — typically 400-1,000 square feet with a bedroom, bathroom, kitchen, and living area. This is the most popular ADU type and offers the most design flexibility.

Garage Conversion ADU

Convert an existing attached or detached garage into a living space. Includes insulation, drywall, flooring, plumbing, electrical, HVAC, kitchen, and bathroom installation within the existing structure.

Attached ADU Addition

Build an ADU that shares one or more walls with the main home but has its own entrance, kitchen, bathroom, and living space. Similar to a home addition but designed as an independent unit.

Basement ADU Conversion

Convert an existing basement into a separate dwelling unit with its own entrance, kitchen, bathroom, and living area. Requires egress windows, fire separation, and independent utility metering in most jurisdictions.

ADU Construction and Boise's housing stock

Boise has over a century of residential construction, from 1900s Craftsman homes in the North End to 2020s new construction in West Boise and Southeast Boise. This diversity means remodeling contractors encounter a wide range of structural systems, plumbing types, electrical standards, and finish materials.

Pre-1940 (North End, Downtown)

Craftsman bungalows, Tudor revivals, and foursquare homes with plaster walls, old-growth fir floors, knob-and-tube wiring (in some), galvanized plumbing, and brick or stone foundations. Remodeling these homes requires sensitivity to historic character while updating systems.

1940s–1960s (Bench, Central Boise)

Post-war ranch homes and split-levels with hardwood floors, original tile bathrooms, copper plumbing, and 100-amp electrical panels. These homes often need kitchen and bathroom updates, electrical upgrades, and insulation improvements.

1970s–1990s (West Boise, South Boise)

Subdivision homes with drywall, builder-grade cabinets, laminate countertops, carpet throughout, and basic builder fixtures. Most plumbing is copper or early PEX. These are the most common candidates for kitchen and bathroom remodels.

2000s–present (SE Boise, Harris Ranch, West Boise)

Modern construction with PEX plumbing, 200-amp panels, energy-efficient windows, and open floor plans. Remodeling in these homes typically focuses on upgrading builder-grade finishes rather than updating systems.

Common issues in Boise homes

•Galvanized plumbing in pre-1970 homes causing low water pressure and corrosion
•Insufficient electrical capacity (100-amp panels) for modern kitchen and bathroom demands
•Poor or missing bathroom ventilation leading to moisture and mold issues
•Closed-off floor plans in 1970s-1990s homes that homeowners want opened up
•Cracked or settling foundations in some older Bench and North End homes
•Builder-grade materials reaching end of life in 1990s-2000s subdivision homes

Materials and options for adu builder in Boise

Material selection affects the look, durability, and cost of your adu builder. Here are the most popular options we install in Boise:

Concrete Slab or Stem Wall Foundation

$8,000–$20,000

Most detached ADUs in Idaho use a concrete slab-on-grade or stem wall foundation depending on lot conditions, frost depth, and plumbing requirements. Garage conversions may use the existing slab with modifications.

Best for: Detached ADU new construction

Standard Wood Framing

$12–$22 per sq ft framed

2x4 or 2x6 wood framing for walls, with trusses for the roof. ADU framing follows the same building codes as primary residences, including insulation requirements, fire separation, and structural standards.

Best for: All ADU types

Mini-Split HVAC System

$3,500–$7,000 installed

The most common heating and cooling solution for ADUs. A ductless mini-split provides efficient heating and cooling with a small exterior compressor and one or two interior wall units. No ductwork required.

Best for: Detached ADUs and garage conversions

Compact Kitchen Package

$5,000–$15,000 complete

ADU kitchens need to be efficient. A compact kitchen typically includes a 24-inch range, apartment-size refrigerator, single-bowl sink, and upper and lower cabinets — all designed to maximize function in a smaller footprint.

Best for: Studio and one-bedroom ADUs

Matching or Complementary Siding

$5–$15 per sq ft installed

The ADU exterior should complement the main home. Options include matching the existing siding exactly, using a contrasting but compatible material, or using a modern material like board-and-batten or metal panel for a contemporary look.

Best for: Seamless property aesthetic

Our adu builder process in Boise

Here is how a typical adu builder project works from first contact to final walkthrough:

Zoning and Feasibility Research

We research your property's zoning designation, lot size, setback requirements, maximum ADU size allowed, parking requirements, and any HOA restrictions. Not every lot qualifies for an ADU, so this step is critical before investing in design.

Concept Design and Budget Planning

Based on feasibility findings, we develop a concept design including floor plan, placement on the lot, utility connection points, and exterior style. You receive a preliminary budget range to confirm the project is viable.

Architectural Plans and Engineering

Detailed architectural plans are prepared including floor plans, elevations, structural engineering, mechanical systems, and site plan. These plans must meet local building codes and will be submitted for permit review.

Permitting and Utility Coordination

We submit plans for permit review, coordinate utility connections (water, sewer, electrical, gas), and manage any required inspections or reviews. ADU permitting can take 4-8 weeks depending on the jurisdiction.

Site Preparation and Foundation

Excavation, grading, utility trenching, and foundation work. For detached ADUs, this typically means a new concrete foundation. Garage conversions may require foundation modifications.

Construction (Framing through Finish)

Complete construction including framing, roofing, siding, windows, insulation, drywall, flooring, kitchen, bathroom, HVAC, electrical, plumbing, and all finish work. The ADU is built to the same code standards as a primary residence.

Final Inspection and Certificate of Occupancy

All required inspections are passed, the certificate of occupancy is issued, and the ADU is ready for use. We provide a complete walkthrough and all warranty documentation.

ADU Construction timeline in Boise

Here is what to expect for project duration when planning a adu builder in Boise:

Phase	Duration	Details
Zoning Research and Feasibility	1–2 weeks	Confirm the property qualifies for an ADU under current zoning, identify setback and size constraints, and determine utility connection feasibility.
Design and Engineering	4–8 weeks	Architectural plans, structural engineering, site plan, and mechanical design. ADU designs must meet full building code requirements.
Permitting	4–8 weeks	Plan review, permit issuance, and any required revisions. ADU permitting timelines vary by jurisdiction in the Treasure Valley.
Site Work and Foundation	2–4 weeks	Excavation, utility trenching, foundation pour, and curing. Weather-dependent in Idaho, especially during winter months.
Framing, Roofing, and Mechanical	4–8 weeks	Framing, roof installation, windows, exterior sheathing, electrical, plumbing, HVAC, and insulation. All rough-in inspections are completed.
Interior Finish and Final Inspection	4–6 weeks	Drywall, paint, flooring, kitchen, bathroom, fixtures, and all finish details. Final inspections and certificate of occupancy.

ADU Construction cost factors in Boise

Typical range: $80,000 – $300,000+

Most projects: $120,000–$200,000

The final cost of your adu builder in Boise depends on several factors. Here are the biggest cost drivers:

ADU Type (Detached vs. Conversion)

high impact

A detached new-construction ADU costs significantly more than a garage conversion because it requires a new foundation, full framing, roofing, and all-new utility connections. Garage conversions leverage the existing structure.

Size (Square Footage)

high impact

ADUs range from 300 sq ft studios to 1,000+ sq ft two-bedroom units. Larger units cost more but provide more rental income potential and livability.

Utility Connections

high impact

Connecting water, sewer, electrical, and gas to the ADU site involves trenching, new service lines, and potentially utility upgrades. Distance from the main house to the ADU affects cost.

Kitchen and Bathroom Complexity

medium impact

Every ADU needs at least a bathroom and kitchen. The finish level — basic vs. mid-range vs. premium — significantly affects the mechanical and finish costs.

Site Conditions and Access

medium impact

Sloped lots, limited access for equipment, rocky soil, or mature trees in the building area can increase site preparation and foundation costs.

Permitting and Impact Fees

medium impact

ADU permit fees, impact fees, and utility connection fees vary by jurisdiction. Some Boise-area jurisdictions have reduced or waived impact fees for ADUs to encourage construction.

Common problems solved by adu builder in Boise

Problem: Need rental income but do not want to move

Solution: A detached ADU on your property generates $800-1,500+ monthly rental income while you continue living in your primary home.

Problem: Aging parents need close but independent living space

Solution: An ADU with a separate entrance provides privacy and independence while keeping family close. Accessibility features can be built in from the start.

Problem: Existing garage is unused and taking up valuable space

Solution: A garage conversion ADU transforms underutilized space into a functional living unit at a lower cost than new construction.

Problem: Need a dedicated workspace separate from the main home

Solution: A detached ADU configured as a studio or office provides the separation remote workers need, with the commute of a backyard walk.

Problem: Want to maximize property value and investment potential

Solution: A well-built ADU adds $100,000+ to property value and generates ongoing rental income — one of the highest-ROI improvements a homeowner can make.

How Boise's climate affects adu builder

Boise has a semi-arid, four-season climate with hot, dry summers (90-105°F), cold winters (15-35°F), and low annual precipitation. This climate directly affects material choices, construction scheduling, and long-term durability of remodeling work.

Temperature Extremes (15°F to 105°F range)

Exterior materials must handle dramatic temperature swings. Windows need strong thermal performance. Interior comfort depends on insulation quality and HVAC sizing.

Low Humidity and Dry Air

Wood materials can dry, shrink, and crack. Hardwood floors may develop gaps in winter. Bathroom ventilation is still critical because bathrooms create localized high-humidity environments.

Freeze-Thaw Cycles

Exterior tile, concrete, and masonry must handle freezing and thawing without cracking. Foundation work has specific frost-depth requirements in the Boise area.

UV Exposure (300+ sunny days)

Exterior paint, siding, and stain fade faster under constant UV. South-facing and west-facing surfaces require UV-resistant materials and more frequent maintenance.

Construction Season

Foundation and exterior work is best scheduled March through November. Interior remodeling can happen year-round. Winter concrete pours require special cold-weather precautions.

ADU Construction across Boise neighborhoods

North End

Boise's most historic and walkable neighborhood, with tree-lined streets, Craftsman bungalows, Tudor revivals, and mid-century homes dating from 1900 to 1960. The North End Historic District adds design review requirements for exterior work.

Common projects in North End:

•Kitchen remodels in older homes with small, closed-off layouts
•Bathroom updates in homes with original 1920s-1950s plumbing
•ADU construction in larger lots for rental income
•Home additions for growing families who love the neighborhood

Southeast Boise / Harris Ranch

A mix of established 1970s-1990s homes and newer master-planned developments like Harris Ranch. Homes range from mid-century ranch-style to modern custom builds with foothills views.

Common projects in Southeast Boise / Harris Ranch:

•Full kitchen renovations upgrading builder-grade finishes
•Primary suite additions in older ranch homes
•Deck and patio construction for outdoor living
•Whole-home remodels bringing 1970s-1980s homes to modern standards

Boise Bench

An elevated neighborhood south of downtown with a mix of post-war homes from the 1940s-1970s and newer infill construction. Known for its views and access to the Greenbelt.

Common projects in Boise Bench:

•Bathroom remodels updating 1950s-1970s fixtures and tile
•Kitchen updates in compact post-war floor plans
•Basement remodels adding usable living space
•Energy efficiency upgrades in older homes with poor insulation

West Boise

A large area with subdivisions spanning from the 1980s through the 2010s. Many homes are builder-grade with standard finishes that homeowners upgrade as the homes age.

Common projects in West Boise:

•Kitchen and bathroom remodels replacing builder-grade finishes
•Open-concept conversions in 1990s closed-layout homes
•Flooring replacement throughout the home
•Exterior painting and siding updates

Permits for adu builder in Boise

Permit authority: City of Boise Planning and Development Services

Online portal: https://pds.cityofboise.org

✓Residential remodeling permits are required for plumbing, electrical, structural, and mechanical changes
✓The North End Historic District requires design review for exterior modifications
✓ADU permits follow specific zoning criteria — lot size, setbacks, parking, and owner-occupancy rules apply
✓Online permit portal allows digital submission and tracking
✓Inspections can be scheduled online with 24-hour advance notice
✓Typical permit processing is 1-2 weeks for standard residential remodels

Design considerations for adu builder

●Lot placement — ADU location affects privacy, natural light, utility run distances, and neighbor sight lines
●Ceiling height — code minimums apply, but taller ceilings (9 ft) make a small ADU feel significantly larger
●Storage planning — ADUs need creative storage: wall-mounted shelving, loft storage, and built-in solutions
●Outdoor space — a small patio, porch, or deck at the ADU entrance adds livability and curb appeal
●Parking — most jurisdictions require at least one off-street parking space for an ADU
●Rental readiness — if the ADU may be rented, plan for durable finishes, separate utility metering, and tenant-friendly design

ADU Construction design trends in Boise

Here are the design trends we see most often in Boise adu builder projects:

→Modern farmhouse and transitional styles blending clean lines with warm textures
→Open-concept kitchen conversions removing walls between kitchen and living areas
→Walk-in showers replacing bathtubs in primary bathrooms
→Matte black and brushed gold fixture finishes replacing brushed nickel
→Large-format tile (12x24+) in bathrooms for a modern, minimal-grout look
→Quartz countertops overtaking granite as the primary kitchen surface
→LVP (luxury vinyl plank) replacing carpet throughout main living areas
→Smart home integration — lighting, thermostats, and security systems

Boise remodeling market context

Boise's housing market has appreciated significantly over the past decade, with median home values rising from approximately $180,000 in 2015 to over $450,000 in recent years. This appreciation makes remodeling an increasingly attractive investment — homeowners can invest $30,000-80,000 in a kitchen or bathroom remodel and see it reflected in their property value. The competitive market also means that updated, well-maintained homes sell faster and for higher prices than comparable homes with outdated finishes.

Why choose Iron Crest Remodel in Boise

✓Licensed general contractor with ADU-specific experience in Idaho

✓In-depth knowledge of local ADU zoning rules across Boise-area jurisdictions

✓Full architectural design and engineering included

✓Complete permitting management from application through certificate of occupancy

✓All trades licensed and insured — foundation, framing, electrical, plumbing, HVAC

✓Post-construction warranty on workmanship and installation

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ADU Construction in Boise — frequently asked questions

Do ADUs require permits and planning approval?

Yes. ADU projects require building permits, plan review, and multiple inspections. In most Boise-area jurisdictions, ADUs also require zoning compliance review to confirm lot size, setbacks, and parking requirements are met. We handle the entire permitting process.

How much does it cost to build an ADU in the Boise area?

A detached new-construction ADU typically costs $120,000-200,000+ in the Boise area, depending on size, finish level, and site conditions. A garage conversion is typically $80,000-150,000. Costs include design, engineering, permitting, construction, and utility connections.

How long does it take to build an ADU?

From start of design to move-in, a typical ADU project takes 6 to 12 months. This includes design (4-8 weeks), permitting (4-8 weeks), and construction (3-5 months). Garage conversions are faster; detached new construction takes longer.

Can I rent out my ADU?

In most Boise-area jurisdictions, yes. ADUs can be rented as long-term rentals. Short-term rental rules (Airbnb, VRBO) vary by city and may have additional restrictions. Check local regulations before planning a short-term rental strategy.

How much rental income can an ADU generate in Boise?

A well-built one-bedroom ADU in the Boise area can generate $800-1,500+ per month in rental income, depending on location, size, finish level, and market conditions. This income can offset or exceed the monthly cost of financing the ADU construction.

What is the maximum size for an ADU?

Maximum ADU size varies by jurisdiction. In Boise, detached ADUs can be up to 1,000 square feet or 10% of the lot area, whichever is less. Other cities in the Treasure Valley have different size limits. We confirm the specific rules for your property during the feasibility phase.

Do I need to live on the property to have an ADU?

Owner-occupancy requirements vary by jurisdiction. Some cities require the property owner to live in either the primary home or the ADU. Others have relaxed or eliminated owner-occupancy requirements. We confirm the rules for your specific location.

Will an ADU increase my property value?

Yes. A permitted, well-constructed ADU typically adds $100,000-200,000+ to property value in the Boise area — often more than the construction cost. ADUs also make a property more attractive to buyers who value rental income potential or multigenerational living flexibility.

Do you work on older homes in Boise?

Yes. We have extensive experience remodeling homes from every era of Boise construction — from 1900s Craftsman homes in the North End to 1970s ranch homes on the Bench to 2000s builder-grade homes in West Boise. Each era presents different structural, plumbing, and electrical considerations that we plan for during the design phase.

Are permits required for remodeling in Boise?

Yes, most remodeling projects that involve plumbing, electrical, structural, or mechanical changes require permits from the City of Boise Planning and Development Services. We handle the entire permit process including application, submission, and inspection coordination.

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