General Building & Remodeling · Property Services

ADU (Accessory Dwelling Unit) Construction

An accessory dwelling unit can house family, produce rental income and add lasting value to a property. California law has made ADUs easier to permit, but the project still involves design, utilities, structure and strict inspections. NorTech connects you with a verified licensed general contractor who walks the property, explains the options and bids the full project in writing.

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Choosing the type of ADU that fits your lot

ADUs come in several forms: a detached backyard unit, an attached addition, a garage conversion or a unit built within existing space. Each has different costs, setback rules and utility needs. A contractor looks at lot size, access, existing structures, slopes, trees and where water, sewer and power lines run. Garage conversions are often the fastest and least expensive path, while detached units offer privacy and more design freedom. Ask for a feasibility review before you commit to design drawings.

Plans, permits and the rules that apply

State law limits how much a city can restrict ADUs, but local rules on height, setbacks, parking and design standards still apply. Most projects need architectural plans, structural calculations, energy compliance documents and sometimes a soils report. The contractor or a design partner prepares and submits them, then responds to plan-check comments. Permit timelines vary by city, so build slack into your schedule. A good bid explains who handles each step and what happens if the city asks for changes.

Budget, schedule and what drives cost

Costs depend on size, finishes, site conditions and utility connections, with sewer and electrical service upgrades often being major line items. Allowances for fixtures, flooring and appliances should be clear in the contract, along with a schedule of payments tied to milestones. Typical construction takes several months after permits, and weather and inspections affect timing. Keep a contingency fund for surprises like rock, drainage or older utilities. Ask for a list of recent ADU projects and speak with past clients.

When to book adu (accessory dwelling unit) construction

You want a rental unit or a place for a parent or adult child.

Your garage is underused and could become a living space.

You have space in the yard for a small detached home.

You want to add value and income to your property.

You need a home office or studio with a kitchen and bath.

You are planning for multigenerational living.

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Frequently asked

ADU (Accessory Dwelling Unit) Construction — common questions

Every lot has different access, utilities, slopes and rules. A licensed contractor must see the property and the plans before writing a realistic scope, schedule and price for the project.

Design and permitting often take several months, and construction usually takes four to eight months after that. Garage conversions are quicker and large detached units take longer, depending on weather and inspections.

Not always. Many cities allow shared utilities, while others require separate meters or upgrades to the electrical service. The contractor checks capacity and local rules during the feasibility review.

In most California cities you can, though some have owner-occupancy rules or limits on short-term rentals. Check local ordinances and talk to your contractor about requirements.

A junior ADU is a small unit within the existing house, typically up to 500 square feet, while an ADU can be larger and detached. The rules, kitchen requirements and permit steps differ.

The contractor guarantees its workmanship for 90 days after completion, covering defects in construction and installation. Manufacturer warranties apply to appliances and materials, and longer statutory protections for construction defects may also apply.

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