How Cities Can Use a Free ADU Lot Check to Answer Resident Questions

Planning staff in any jurisdiction with an ADU ordinance hear the same handful of questions, by phone, by email and at the counter:

• Can I build an ADU on my lot?
• How close to the property line can it go?
• How big can it be, and does the size cap depend on my house or my lot?
• Does it need parking? Can it be detached, or over the garage?
• What do I do next, and what should I bring?

None of these is hard for staff to answer, but each one depends on a specific parcel. Answering well means pulling up the parcel, confirming the zone, finding the right code section and walking the resident through the setbacks. Many of these conversations end the same way: "it depends on your site; come back with a site plan." There is also a quieter risk. A resident who hears "probably" over the phone may pay for design before anyone has looked closely at the parcel, and the first time the setbacks are checked is at submittal.

State law has made these questions more common. In California, state ADU law requires local agencies to approve or deny a complete ADU application within 60 days, and to run a program for pre-approved ADU plans; the HCD ADU Handbook explains both. In Colorado, HB24-1152 requires subject jurisdictions to allow one ADU with a single-unit detached home, through an administrative approval process, wherever single-unit detached homes are allowed. As more lots become eligible, more residents want to know whether theirs is one of them.

The lot check at aduinsights.com works for any U.S. address. It uses county lot lines, researched local ADU rules where we have them, and state ADU law in about 20 states. Researched local rules currently cover parts of Colorado and California, for example Grand Junction and Mesa County, many Los Angeles County and Orange County cities, and cities around Sacramento. The data sources page lists where lot checks work and where the data comes from.

For an address, the resident sees:

• Lot lines drawn from county parcel maps over aerial imagery.
• Buildable area, the part of the lot left after the setbacks that apply to an ADU.
• The rules, with sources. Setbacks, size limits and other standards in plain language, each linked to the code section or statute it comes from, with the exact wording and the date it was checked.
• Plans to scale. Sample ADU footprints placed on the lot, showing which ones fit. The resident can move and rotate them and see the distance to each lot line and to the house.
• A 3D view of the house, the ADU and the lot.
• A cost estimate, labeled as an estimate and not a quote, with assumptions the resident can change.
• A site plan and report, stamped "Preliminary · Not for permit · Not a survey" on the sheet.

Residents can run the check and read the results on screen without creating an account. If they want the full report, it is sent by email.

Plain words matter here, because residents will repeat what they read. The lot check is:

• Not a permit and not a permit decision.
• Not a survey. County parcel maps can be off by several feet. A licensed surveyor sets the true lines.
• Not a zoning determination. It applies published rules to public map data. Only your staff can interpret your code for a specific parcel.
• Not an engineered plan. Utilities, drainage, easements and structural questions are confirmed on site.
• Not a binding quote. Costs are estimates for planning only.

Two more limits matter to a city. First, the free tool is not configured for your jurisdiction and has not been reviewed by your staff. Where we have researched your local rules, they are written from your published code with the section cited and the date checked, but your staff have not signed off on them. Second, the free tool is our general homeowner tool. It includes an optional, unticked box a resident can tick if they want an ADU builder to contact them; nothing is shared unless they tick it. A city that wants a fully neutral version, with no builder path at all, is describing a city portal, covered in Turning your adopted ADU code into a resident self-service portal.

Linking to a free tool does not hand any decision to it. Every screen and every report says the results are preliminary and points the resident back to the planning department. Staff can reinforce that with how the link is presented.

Suggested wording for your ADU web page:

Thinking about an ADU? This free online lot check gives a preliminary picture of your lot: lot lines, setbacks and the ADU rules that may apply, with sources. It is not a permit, a survey or a zoning determination, and it is not a city service. Contact the Planning Division to confirm what applies to your property.

A few practices keep the roles clear:

• Treat it as preparation, not an answer. The lot check helps a resident ask a better question. The answer still comes from your office.
• Ask residents to bring what they printed. A preliminary site plan gives a pre-application conversation a starting point, and staff can correct it on the spot.
• Tell us when a rule is wrong. If staff see a rule, setback or source that doesn't match your adopted code, our corrections policy explains how we fix it.
• Be clear about the order of steps. Residents should confirm the rules for their lot with your office before they pay for design. Permit drawings come from a licensed designer or engineer, not from a lot check.
• Keep your own materials first. Link the lot check alongside your handouts, fee schedule and application checklist, not in place of them.

A city does not need a contract or a set-up project to point residents to the free lot check. Practical steps:

1. Add a link on your ADU program page, with the wording above.
2. Give counter and phone staff a one-line script: "You can get a preliminary look at your lot at aduinsights.com before we meet; bring what you find."
3. Mention it in pre-application meeting confirmations, so residents arrive with a lot picture and a list of questions.
4. Review the rules shown for a few addresses you know well, and tell us about anything that doesn't match.
5. Revisit the link whenever your ADU code changes, so your page wording and your handouts stay in step with what residents read.

The American Planning Association's ADU resources and the California HCD ADU page are good companions on the same page, because they explain the policy side that a lot check doesn't.

The free lot check is general by design. A jurisdiction that wants residents to see its own adopted code, its own parcel data, its own approved plans and its own next step can request a portal set up for it. That version is builder-neutral, with no builder names, ads or rankings and no lead capture by default, and it ends every visit with your office. Staff review every rule before launch.

The city portal is offered today as a demo and pilot set-up; it is configured per jurisdiction and reviewed by staff before anything goes live. You can watch the resident portal demo, which uses a fictional city name on a sample lot in Grand Junction, Colorado, with that city's published rules; Grand Junction is not a customer. How an ADU portal helps a planning department save time and improve applications covers what a portal changes for staff, and For Municipalities covers how it works.

To see it on addresses in your area, request a demo tailored to your jurisdiction.