ADU Construction Services

An ADU (Accessory Dwelling Unit) is a smart way to add flexible living space and long-term value to your property.

Whether you’re planning for multigenerational living, guest accommodations, or rental income, a well-designed ADU should feel comfortable, private, and fully functional.

Our design-build team helps homeowners navigate ADU planning, permitting, and construction by coordinating design, structure, and utilities from the start.

 

ADU Design & Planning

  • As a full-service design-build firm, our designers translate your ADU goals into a clear, buildable plan.

  • We guide you through layout options, finish selections, and budget decisions while designing for livability and long-term performance.

Detached ADUs (Backyard Cottages)

  • Build a standalone ADU that offers privacy and independence with a fully self-contained living space.

  • Detached ADUs are ideal for rental units, guest houses, or creating space without altering your main home’s footprint.

Garage Conversions

  • Convert an existing garage into a finished ADU with a kitchen, bathroom, and comfortable living area.

  • Garage conversions can be an efficient path to adding usable square footage while maximizing your existing structure.

Attached ADUs

  • An attached ADU expands your home while maintaining separation between living spaces.

  • These additions can be designed for family members, long-term guests, or future flexibility as your needs change.

Basement ADUs

  • Transform an underused basement into a functional ADU with thoughtful layout, lighting, and upgraded systems.

  • Basement additions or ADUs often require careful planning for ceiling height, egress, moisture control, and ventilation.

In-Law Suites

  • Create a private, comfortable space for extended family that supports independence while keeping loved ones close.

  • In-law suite ADUs can include a bedroom, bathroom, kitchenette, and accessible design features for aging-in-place.

Rental-Ready ADUs

  • Design an ADU that’s optimized for long-term renters or short-term stays with durable materials and efficient layouts.

  • We help plan storage, laundry, sound separation, and finishes that hold up to daily use and reduce maintenance.

What Goes
Into ADU Construction?

Building an ADU (Accessory Dwelling Unit) requires planning a fully independent living space with its own utilities, access, and code requirements.

A successful ADU project balances livability, privacy, and long-term durability while working within local regulations and the constraints of your existing property.

ADU Feasibility & Site Planning

Every ADU starts with understanding what your property can support, including lot layout, access points, and where the unit can be placed. This step helps determine whether a detached ADU, garage conversion, or basement ADU is the best fit.

Zoning, Permitting & ADU Code Requirements

ADUs must meet local zoning rules and building codes that can affect size, height, setbacks, and parking requirements. Early permitting coordination helps prevent redesigns and keeps the project moving forward.

Utility Connections & System Planning

Because an ADU functions as a separate living space, utilities often need to be extended, upgraded, or separated. This includes electrical capacity, plumbing tie-ins, HVAC strategy, and planning for water heater and laundry needs.

Independent Living Features (Kitchen + Bath)

Most ADUs include a full kitchen and bathroom, which require careful layout planning for plumbing, ventilation, and efficient use of space. Durable finishes and smart storage choices help the ADU live comfortably without feeling cramped.

Privacy, Access & Entry Design

ADU construction needs to consider how the unit will be accessed and how private it will feel from the main home. Thoughtful placement of entrances, windows, and outdoor space can make the ADU feel like a true standalone residence.

Long-Term Performance & Comfort

ADUs should be built for everyday living, with proper insulation, sound control, moisture management, and ventilation. These details improve comfort for occupants and reduce maintenance issues over time—especially in smaller spaces.

Although our project was a relatively small budget project, none the less, completing the project on budget was a highlight of the job Lamont Bros. did for us.
 
Our project was the conversion of a 50+ year old garage to a legal ADU. Other contractors told us it couldn't be done due to the inherent problems of meeting current building codes.
 
Lamont, however, successfully navigated the permit process with the city and obtained the necessary permits.
 
At all times, everybody acted and communicated in a professional and courteous manner, without exception.

– Donald R. | Houzz Review

Here's How The Design-Build Process Works:

1

Our design team creates the space of your dreams.

2

Our build team brings the vision to life.

3

You enjoy your new custom-built space.

 

Lamont Bros. | ADU Construction Project Gallery

ADU Design & Construction Examples

These ADU projects highlight how thoughtful design and careful planning can create comfortable, fully independent living spaces on an existing property.

Each accessory dwelling unit was designed to balance privacy, functionality, and long-term durability while fitting naturally into the homeowner’s site and lifestyle needs.

From layout decisions to finishes and utility coordination, these ADUs reflect the details that make small spaces live well.

See more projects here: ADU Portfolio

Southwest-Inspired Basement Suite
Basement

Southwest-Inspired Basement Suite

Clackamas Crawlspace Conversion
Basement

Clackamas Crawlspace Conversion
Basement Family Room
Basement

Basement Family Room

Woodlawn ADU
ADU

Woodlawn ADU
Beaumont-Wilshire ADU Conversion
ADU

Beaumont-Wilshire ADU Conversion
Basement Apartment
Basement

Basement Apartment

icon_money

How much do ADUs cost?

Go to our cost calculator

ADU Design and Construction FAQs

Can I build an ADU on my property?

In many cases, yes—but it depends on zoning rules, your lot size, setbacks, and where the ADU would be located. We start by confirming feasibility so you know what’s realistically possible before design begins.

 

Should I build a detached ADU or convert an existing space?

Detached ADUs offer the most privacy and flexibility, while garage or basement conversions can reduce structural work by using an existing footprint. The best option depends on your property layout, budget, and how you plan to use the space.

 

Do ADUs require separate utilities?

Not always, but utility planning is a big part of ADU construction. Depending on the project, we may extend existing services or explore options like separate metering for long-term rental use.

 

Can an ADU be used as a rental?

Often, yes. Many homeowners build ADUs specifically for long-term rental income. Local rules can affect rental use, so we help you plan the space with those requirements in mind.

 

How much does it cost to build an ADU?

ADU costs depend on size, site conditions, utility work, and finish selections. We help clarify costs early so you can make informed decisions about scope and priorities before construction starts.