ADU Construction in Phoenix, AZ
Custom-designed accessory dwelling units built to match your home, maximize your property, and generate rental income.
Custom ADU Builder
Add Living Space, Income & Property Value
An accessory dwelling unit is one of the smartest investments a Phoenix homeowner can make. Whether you need a private retreat for aging parents, a rental property that generates passive income, a dedicated home office, or a detached casita for visiting family, Kelso Custom Builders designs and builds ADUs that feel like a natural extension of your home — not an afterthought.
Since 2008, owner Mark Kelso has personally managed every ADU project we have built across the Phoenix metropolitan area. That means you work directly with the person who understands your vision, navigates the permitting process, and is on-site every day to ensure the quality matches the plan. We never subcontract project management to someone you have never met.
Our design-build approach covers everything under one roof: initial consultation, architectural design, 3D renderings, structural engineering, city permitting, utility coordination, and full construction. There are no gaps between the design team and the build crew because they are the same team.
ADU Types We Build
Every Style of Accessory Dwelling Unit
From compact backyard studios to full-sized detached homes, we build every type of ADU that Arizona zoning allows — and we handle the permitting to prove it.
Detached ADUs
A fully independent structure on your lot with its own entrance, utilities, kitchen, and bathroom. Ideal for long-term rentals, Airbnb income, or multigenerational living where both households want complete privacy.
Attached ADUs
Built onto the side or rear of your existing home, an attached ADU shares a wall but has a separate entrance. This option is often more affordable because it leverages the existing foundation and utilities while still providing full autonomy for occupants.
Backyard Casitas
The quintessential Arizona guest house. A casita is typically 400 to 800 square feet and designed with desert living in mind — covered patios, low-maintenance landscaping integration, and interiors that stay cool without oversized HVAC systems.
Garage Conversions
Convert an existing attached or detached garage into a fully permitted living space. We handle structural modifications, insulation upgrades, plumbing and electrical additions, and finish work to create a comfortable, code-compliant unit.
Arizona ADU Regulations
Navigating Phoenix ADU Rules & Permitting
Arizona made national headlines in 2023 when Governor Hobbs signed legislation requiring all municipalities to allow ADUs on single-family residential lots. The new law streamlined zoning restrictions that had previously made ADU construction difficult in many Phoenix-area cities.
That said, every jurisdiction still has its own setback requirements, lot coverage maximums, height restrictions, and parking stipulations. In Phoenix proper, for example, ADUs must comply with the underlying zoning district's building envelope. In Scottsdale, design review boards may weigh in on exterior materials and colors. Maricopa County unincorporated areas have their own set of guidelines entirely.
Kelso Custom Builders has navigated permitting in virtually every city and town in the greater Phoenix metro. We know which jurisdictions move quickly, which ones require additional engineering documentation, and how to design from day one for approval — not revision after revision. Our permit approval rate speaks for itself, and our clients never pay for redesigns caused by our mistakes.
Built for the Desert
Phoenix summers push temperatures well above 110 degrees Fahrenheit, and our monsoon season brings sudden wind, rain, and dust storms. Every ADU we build is engineered specifically for Maricopa County's climate: high-efficiency HVAC systems sized for extreme heat, radiant barrier roof decking, low-E dual-pane windows, stucco or masonry exteriors that handle thermal cycling, and drainage plans that account for monsoon flow. We do not build cookie-cutter units designed for temperate climates and hope they survive in Arizona — we build for this desert from the ground up.
Rental Income Potential
Turn Your Backyard Into a Revenue Stream
The Phoenix metro area has one of the strongest rental markets in the country. A well-designed ADU can pay for itself within a few years while increasing your property's resale value by 20% to 35%.
Long-Term Rentals
One- and two-bedroom ADUs in the Phoenix metro command $1,200 to $2,200 per month in long-term rent, depending on the area and finishes. That steady income stream helps offset your mortgage, fund retirement, or simply improve monthly cash flow.
Short-Term Rentals
Phoenix's tourism season from October through April makes short-term rentals highly lucrative. A well-furnished, well-located ADU can generate $3,000 to $5,000 per month during peak season through platforms like Airbnb and VRBO.
Property Value Boost
Beyond rental income, a permitted ADU adds real, appraised square footage to your property. In a market where lot sizes are fixed and new construction is expensive, additional livable space is one of the most reliable ways to build long-term equity.
Our Process
From Concept to Keys in 6–7 Months
We manage every phase so you have one point of contact, one timeline, and zero confusion about what happens next.
Free Consultation
We visit your property, discuss your goals, review the lot for setbacks and utility access, and talk budget. You will leave this meeting knowing whether an ADU is feasible and roughly what it will cost.
Design & Engineering
Our design team creates floor plans, elevations, and 3D renderings so you can see exactly what your ADU will look like before a single shovel hits the ground. We finalize materials, finishes, and structural engineering.
Permitting
We submit the full permit package to your city or county, respond to plan review comments, and keep the process moving. Most Phoenix-area jurisdictions issue ADU permits within 4 to 6 weeks.
Construction
Mark Kelso is on-site every day during construction. We coordinate all trades, schedule inspections, and keep you updated with regular progress reports. Typical ADU construction takes 4 to 5 months from groundbreaking.
Final Walkthrough & Handoff
We walk through the finished unit with you, address any punch-list items, and hand over the keys along with all warranty documentation, permits, and inspection records.
Common Questions
ADU Construction FAQ
ADU construction in the Phoenix metro typically ranges from $150 to $350 per square foot depending on the size, finishes, site conditions, and whether utilities need to be extended. A basic 400-square-foot studio unit starts around $80,000, while a fully appointed 1,200-square-foot two-bedroom unit with high-end finishes can reach $300,000 or more. We provide detailed, transparent estimates before any work begins so there are never surprises.
From design to move-in, most ADU projects take between 6 and 7 months. This includes roughly 4 to 6 weeks for design and permitting, followed by 4 to 5 months of on-site construction. Timelines can vary based on project complexity, permitting backlogs at the local jurisdiction, and material lead times. We give you a detailed schedule at the start and communicate proactively if anything changes.
Yes. Arizona state law permits homeowners to rent ADUs as long-term rentals statewide. Short-term rental rules vary by municipality — Phoenix, Scottsdale, and most Maricopa County cities allow short-term rentals with proper registration and tax collection. We help clients understand the specific regulations for their area during the planning phase so you can make informed decisions about how you will use the unit.
Yes, ADU construction requires building permits from your local jurisdiction. Arizona's 2023 ADU-friendly legislation streamlined the process statewide, but requirements still differ between cities. Kelso Custom Builders handles all permitting as part of our design-build service, including site plans, structural engineering, and city submissions. You never have to stand in line at city hall.
Absolutely. We specialize in designing ADUs that complement the architectural style, roofline, materials, and color palette of the existing home. Whether your primary residence is a Spanish Colonial, desert contemporary, ranch-style, or Santa Fe adobe, we create a cohesive look so the ADU feels like it was always part of the property rather than a tacked-on addition.
Studies consistently show that a well-built ADU can increase property value by 20% to 35%, depending on the local market and the quality of the build. In the Phoenix metro area, where housing demand remains strong and rental yields are attractive, ADUs offer both immediate rental income and long-term equity growth. It is one of the highest-ROI improvements a homeowner can make.
Client Testimonials
What Our Clients Say
"Great communication, great guy, gets job done in very very timely fashion."
"Very responsive and thorough. Patiently educates homeowner. Creative suggestions."
"Great guy, very easy to work with and understands what you are trying to accomplish."
Start Your ADU Project Today
Whether you are exploring your options or ready to break ground, Kelso Custom Builders is here to help. We offer free, no-obligation consultations where Mark will visit your property, discuss your goals, and provide an honest assessment of what is possible on your lot.
With 17+ years of experience, AZ ROC License #318269, and a portfolio of completed ADUs across the Phoenix metro, you can trust that your project is in the right hands from day one.
Call us directly at (602) 361-2310 or fill out the form and we will get back to you within one business day.