Getting it permitted

Who to hire for your ADU, and how to check them

Checked against state laws and official agency sources · Last reviewed October 9, 2026

Who does what

• Architect: plans and designs buildings. In California, "any person who uses the title of architect, or advertises to provide architectural services in California, must be licensed by CAB," the California Architects Board.
• Engineer: In California, civil engineers "may design any building except hospitals and public schools," and structural engineers have "no limitations."
• Designer (not licensed): In California, an unlicensed person may design "single-family dwellings of wood frame construction not more than two stories and a basement in height," plus garages and similar structures that go with them. They "may not design any component that changes or affects the safety of any building, including but not limited to structural or seismic components."
• General contractor: builds the project. CSLB says "contractors generally pull the permits" (see below).
• Permit expediter: a paid helper who deals with the city on your permit (see below).

CAB suggests asking your local building department whether your project needs "a licensed architect or engineer to prepare and submit plans." The answer can depend on "snow loads, winds, earthquake activity, tidal action, flood hazard zones, and soil conditions." Rules outside California differ, so ask your city. [1][3]

Contractors must be licensed or registered

Each state has its own rule:

• California: The Contractors State License Board (CSLB) licenses contractors. CSLB says your contract should include "the contractor's license number."
• Washington: "Every contractor shall register with the department" of Labor & Industries.
• Oregon: A contractor "must have a current license issued by the Construction Contractors Board."
• Arizona: It is unlawful to act as a contractor "without having a contractor's license in good standing," unless exempt.
• Montana: Since January 1, 2026, construction contractors "are required to be licensed with the Montana Department of Labor & Industry." The license replaced the old registration system.
• Massachusetts: "No contractor or subcontractor shall undertake, offer to undertake, or agree to perform residential contracting services unless registered." This covers work on an existing owner-occupied home with one to four units, and "structures which are adjacent."
• Colorado: Check with your city. Denver, for example, issues its own contractor licenses and "does not accept or reciprocate contractor licenses and/or certificates from other counties or states." Electrical and plumbing licenses come from the state's Department of Regulatory Agencies (DORA).
• Texas: The state's licensing agency (TDLR) licenses electricians and air conditioning contractors. Plumbers are licensed by the Texas State Board of Plumbing Examiners. Ask your city what it requires of builders.

[2][3][4][5][6][7][8][9][10][11][12][13]

Check the license before you sign

Use your state's free lookup tool:

• California: CSLB license check for contractors. Use the California Architects Board to check that an architect is licensed.
• Washington: L&I Verify a Contractor. L&I says to check that the contractor has an active license, "is bonded and insured," and has no notable lawsuits or license violations.
• Oregon: CCB license search. The CCB warns, "Anyone can pretend to be a contractor. Check licenses."
• Arizona: Registrar of Contractors contractor search, linked from the Registrar of Contractors website. You can also call the Registrar at 1-877-692-9762.
• Montana: Licensee Lookup System. The state notes that "some disciplinary actions may not be immediately posted."
• Massachusetts: Ask for the contractor's state registration. Contracts must include a notice "that all contractors and subcontractors must be registered."
• Colorado: Denver Contractor Licensing for Denver jobs, or (720) 865-2770. Check electricians and plumbers at the Colorado Division of Professions and Occupations ("Verify a License").
• Texas: TDLR license search for electricians and AC contractors. Check plumbers with the TSBPE public license search.

[1][2][7][10][11][12][13][14][15][16][17][18]

Prefab and factory-built ADUs

A factory-built home can be an ADU. California's housing department says "by definition, an ADU includes manufactured homes." Freddie Mac says low- and moderate-income borrowers "can use CHOICERenovation to add a factory-built ADU to their property."

A prefab unit still needs local approval. In California, "no building or structure may be erected, constructed, enlarged, altered, repaired, moved, improved, removed, converted or demolished unless a separate permit for each building or structure has first been obtained from the building official." Ask the prefab company what it handles (design, permits, foundation, utility hookups) and who does the rest. See our prefab ADU guide. [19][20][21]

Permit expediters, and free help from your city

A permit expediter is someone you pay to deal with the city on your permit. In San Francisco, paid permit helpers are called "permit consultants": people paid for "any contact with the Department of Building Inspection, the Entertainment Commission, the Planning Department or the Department of Public Works to help a permit applicant obtain a permit." There, they must register and file quarterly reports with the Ethics Commission. Licensed architects or engineers of record, and a contractor responsible for all the construction, are not counted as permit consultants.

Before you pay for help, check what your city offers:

• Portland: free 15-minute appointments to "learn about building codes, zoning rules, and permit requirements before you apply," online, by phone or in person. See our Portland page.
• Seattle: SDCI's online services include live chat for "attached and detached dwelling unit construction questions." See our Seattle page.
• California pre-approved plans: Cities must post "preapproved ADU plans" on their websites. A detached ADU using one must be approved or denied within 30 days.
• California state help: HCD's ADU team takes technical assistance requests through its ADU portal ("Contact the ADU Team") once you have an application in.

For the steps, see the ADU permit process. [19][22][23][24]

Contracts, payments and who pulls the permit

Get it in writing. Washington's L&I says to "get a written contract, and make sure you understand the terms," to get at least three written bids, and to "consider requesting a performance bond for larger projects."

California contracts. CSLB says your contract should list the contractor's license number and "who will be responsible for obtaining local building permits and associated fees (contractors generally pull the permits)." It should also list warranties, a payment schedule and realistic timelines. The legal down payment "is $1,000 or 10% of the contract price, whichever is less," unless the contractor has a blanket performance and payment bond on file with CSLB. CSLB also advises: "don't pay for work prior to completion."

Massachusetts contracts. Residential contracting deals over $1,000 "shall be in writing." A deposit "shall not exceed the greater of one-third of the total contract price or the actual cost of any materials or equipment of a special order or custom made nature." The contractor must tell you about all needed permits and that "it shall be the obligation of the contractor to obtain said permits." Homeowners "who secure their own permits will be excluded from the guaranty fund."

Pulling the permit yourself. CSLB says that as an owner-builder you take on "legal obligations and risks" and the job responsibilities of running your own construction. It warns: "Be wary of 'consultants' or unlicensed individuals who will try to talk you into becoming an owner-builder as a way to save money."

Insurance. CSLB says commercial general liability insurance "is recommended but not required." It suggests you "find out if your homeowner policy will cover liability and damages if the contractor is not covered." [3][14][18][25]

Questions people ask