ADU Construction in Nampa, 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
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.
Nampa 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
Not every adu builder project is the same. Here are the most common project types we complete in Nampa:
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.
Nampa has the most diverse housing stock in Canyon County, spanning from early 1900s farmhouses and bungalows to brand-new subdivision homes. This diversity means every project has unique structural and system considerations.
Pre-1950 (Downtown, older neighborhoods)
Bungalows, farmhouses, and early-century homes with plaster walls, hardwood floors, and older plumbing and electrical systems. These homes need system upgrades alongside cosmetic updates.
1960s–1980s (Northwest Nampa, established neighborhoods)
Ranch homes and split-levels with original tile, carpet, and basic finishes. Plumbing is copper or early PEX. Electrical may need panel upgrades for modern kitchen and bathroom demands.
1990s–2010s (South Nampa, newer subdivisions)
Builder-grade subdivision homes with standard finishes. Similar to Meridian's housing stock — ready for finish upgrades as the homes age.
2015–present
New construction with modern systems and open floor plans. Homeowners upgrade finishes 3-5 years after purchase.
Common issues in Nampa homes
- •Older plumbing systems (galvanized pipe, cast iron drains) in pre-1970 homes
- •Insufficient electrical panels in older homes
- •Foundation settling in some older downtown-area homes
- •Builder-grade finishes wearing out in 2000s-era homes
- •Small, closed-off kitchens in older floor plans
- •Inadequate insulation in pre-1990 construction
Material selection affects the look, durability, and cost of your adu builder. Here are the most popular options we install in Nampa:
Concrete Slab or Stem Wall Foundation
$8,000–$20,000Most 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 framed2x4 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 installedThe 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 completeADU 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 installedThe 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
Here is how a typical adu builder project works from first contact to final walkthrough:
1
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.
2
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.
3
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.
4
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.
5
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.
6
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.
7
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.
Here is what to expect for project duration when planning a adu builder in Nampa:
| 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. |
Typical range: $80,000 – $300,000+
Most projects: $120,000–$200,000
The final cost of your adu builder in Nampa depends on several factors. Here are the biggest cost drivers:
ADU Type (Detached vs. Conversion)
high impactA 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 impactADUs 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 impactConnecting 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 impactEvery 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 impactSloped 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 impactADU 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.
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.
Nampa shares the Treasure Valley's semi-arid climate. Canyon County locations may be slightly warmer in summer and experience more wind than Ada County locations closer to the foothills.
Summer Heat
Nampa tends to run 2-3°F warmer than central Boise in summer. HVAC sizing and window quality matter for comfort and energy costs.
Agricultural Dust
Proximity to active farmland means more dust exposure for exterior surfaces. Durable, cleanable exterior finishes are preferred.
Freeze-Thaw
Same frost-depth and freeze-thaw considerations as Boise for foundations, exterior tile, and plumbing in exterior walls.
South Nampa
Newer subdivisions built from 2005 to present. Similar to South Meridian — builder-grade homes that homeowners customize and upgrade over time.
Common projects in South Nampa:
- •Kitchen upgrades replacing builder-grade finishes
- •Bathroom remodels with tub-to-shower conversions
- •Flooring replacement throughout
- •Deck and patio construction
Northwest Nampa
A mix of established neighborhoods with homes from the 1970s-2000s. Some areas are seeing significant investment and revitalization.
Common projects in Northwest Nampa:
- •Full kitchen renovations in 1970s-1990s homes
- •Bathroom remodels addressing outdated fixtures and tile
- •Home additions for growing families
- •Whole-home updates bringing older homes to current standards
Downtown Nampa
The historic downtown core with older homes, some dating to the early 1900s. A revitalizing area with a mix of renovation and new construction.
Common projects in Downtown Nampa:
- •Historic home renovations preserving character while updating systems
- •Kitchen remodels in homes with small, outdated layouts
- •Bathroom remodels replacing original plumbing and fixtures
- •ADU construction for rental income in the revitalizing downtown area
Permit authority: City of Nampa Building Department
Online portal: https://www.cityofnampa.us/building
- ✓Permits required for plumbing, electrical, structural, and mechanical changes
- ✓Permit fees are generally lower than Ada County jurisdictions
- ✓Standard residential permit processing is typically 1-2 weeks
- ✓ADU construction is subject to zoning review
- ✓Online permit application available
- ●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
Here are the design trends we see most often in Nampa adu builder projects:
- →Value-driven upgrades that balance quality with budget
- →Modern farmhouse aesthetics popular in newer homes
- →White and gray kitchen palettes replacing oak and Tuscan styles
- →Walk-in showers replacing tub/shower combos
- →LVP flooring throughout main living areas
- →Energy efficiency upgrades — windows, insulation, HVAC
- →Practical storage solutions in kitchens and bathrooms
Nampa offers some of the most affordable housing in the Treasure Valley, making it attractive for first-time homeowners and investors. Lower purchase prices mean remodeling can represent a larger percentage of home value — making strategic upgrades especially impactful for equity building. The market is strong for updated homes; buyers pay a premium for move-in-ready properties with modern kitchens and bathrooms.
✓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
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.
Are value-focused remodels common in Nampa?
Yes. Many Nampa homeowners prioritize practical upgrades that improve daily function and property value without overbuilding for the market. We help homeowners find the right balance between upgrade quality and budget to maximize both enjoyment and investment return.
Do older Nampa homes need special remodeling considerations?
Yes. Homes built before 1970 may have galvanized plumbing, insufficient electrical capacity, and older insulation that should be addressed during a remodel. We evaluate existing systems during the design phase and include necessary upgrades in the scope and budget.
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