What do you want the ADU to do?
A place for a parent, a rental, and a future home for yourself can lead to different decisions. For a parent, a convenient entrance and bathroom layout may come first. For a rental, privacy, laundry, storage and utility billing may matter more. Write down the use before choosing a floor plan.
Keep the first description short: who will live there, roughly how much space they need, and the features you would miss if they were removed. Separate those from preferences you could change to keep the project affordable.
Choose a direction, not every detail
Think about a detached building, an addition, or converting space you already have. A customized design describes how individualized the plans are; it can be detached, attached or a conversion. A standard plan and a custom design should not be compared as though they include the same design work.
One team or separate design help?
If you want one point of contact, ask an ADU Contractor which design and permit services they actually provide, who performs them, and what you receive before committing to construction. If a specific layout matters most, a separate designer may be a useful first conversation.
Ask whether you can keep and use the drawings if you choose a different builder later. This is a contract question, not something the words “design-build” answer on their own.
A preapproved plan still needs to fit the site. Los Angeles describes a property-specific review for zoning and foundation needs even when a standard plan is used. City of Los Angeles: ADU resources and standard plans
Bring what you already know about the property
Bring the address, photos of the yard or existing garage, and any plans or permit records you have. Point out things you already know: a slope, an old structure to remove, a narrow side yard, or an existing septic system. “I’m not sure” is a useful answer when it tells the team what needs checking.
Ask the Contractor what they can assess during a visit and what needs a separate investigation. Keep a short list of unresolved items and who will check each one. There is no reason to turn a first conversation into a technical test for the homeowner.
See which site conditions can change an ADU quote. Find the right City or County source.
Understand the whole project cost
A construction price may leave out design, permit fees, utility work, appliances you buy yourself, and work around the new building. Before deciding whether you can afford the ADU, ask what sits outside the quoted price and what has not been priced yet.
A $240/sq ft quote and a $300/sq ft quote may describe different work. Ask which floor area is used and whether each includes the same site work, finishes and allowances. A lower rate alone does not tell you what you will spend. See an example of comparing the two quotes.
| Part of the project | What you want to learn |
|---|---|
| Design and approvals | What services and agency fees sit outside construction? |
| Site and utilities | What has been checked, what is assumed, and what remains unknown? |
| The building | What size, finish level, appliances and allowance amounts are included? |
| Your own purchases and reserve | What will you buy directly, and what money remains available if assumptions change? |
For timing, ask for separate expectations for design, approvals, construction and getting the finished ADU ready to use. Ask what must happen before the next part starts. A utility appointment or unresolved design decision can affect a date even when the building work itself is straightforward.
ADU Rental Calculator
Compare rental income with project costs. Use rents from similar homes in your city, then try a lower-rent scenario too.
What you’ll be clear about
- The ADU you have in mind and what matters most to you.
- Which choices you can simplify and which need a professional’s review.
- A starting cost and timing range, including the items still unknown.
- Whether your next conversation should be with a designer or an ADU Contractor offering design help.
Move to the next Step when you can explain the project well enough for that conversation. You do not need approved plans simply to start learning about possible Contractors.
Your ADU idea checklist
Use these prompts when you talk with your project team. Keep technical findings and official approvals with the people qualified to provide them.
Your checkmarks stay on this page until you leave. Download the blank PDF or print your checked copy to keep it.
Questions about this topic
Do I need plans before talking to a Contractor?
No. An early conversation can help define the project and design services you need. Ask whether a price is an initial budget discussion or a bid tied to specific drawings and assumptions.
Read more: How to read ADU bids and pricingLink to this answerWhat if I don’t know my budget yet?
Start by explaining what you want and asking which choices have the largest effect on cost. Request the assumptions behind an early range, then decide whether to simplify the project or investigate further.
Read more: ADU site conditions that can change a quoteLink to this answerSources and review notes
Official references checked on . Inline links identify the source for specific statements.
Prepared for PrepareToBuild.info as an editorial draft, assisted by AI. Not yet reviewed by a licensed construction or legal professional. Practical examples are illustrative, not actual quotes, legal terms or completed projects. Confirm requirements with the responsible agency and get qualified advice about your property, contract or finances.