Choosing an ADU plan is exciting. It can make a future backyard home, rental unit, guest suite, or family space feel real. But before you apply for a permit, you need to verify more than the floor plan.
A pre-approved ADU plan can save time during early research, but it is not a substitute for local confirmation. Your property still has to meet site-specific requirements, and your city or county may require additional documents.
Use this checklist before you commit to a plan. For a better starting point, search local plan listings through ADU Plan Finder, which organizes public ADU plan records by location and links back to official sources when available.
1. Verify the correct jurisdiction
Confirm whether your property is inside city limits or in an unincorporated county area. This affects which ADU rules, plan catalogs, and permit processes apply.
Do not rely only on a mailing address. Use a parcel lookup tool or contact the local planning department if needed.
2. Verify local plan acceptance
A plan may be attractive, but is it accepted in your city or county? Look for accepted-location details, not just a design name.
Use local pages on ADU Plan Finder to compare plan listings by city and county, then confirm with the official source.
3. Verify the official source
A reliable plan record should connect to a public source whenever possible. That source may be a city page, county page, official PDF, plan catalog, provider-linked record, or public program page.
Open the source. Check whether it is current. Look for update dates, program notes, and restrictions.
4. Verify the plan status
Plans may be listed as pre-approved, accepted, standard plan, pending review, or another status. These labels can vary by program.
Do not assume every label means the same thing. Ask the local building department what the status means in your jurisdiction.
5. Verify size and bedroom count
Square footage and bedroom count affect budget, use, privacy, rent potential, and construction complexity. A larger unit may offer more flexibility but can create more site constraints.
Compare plan size to your property, not just your wish list.
6. Verify bathroom and kitchen information
Some sources publish detailed bathroom and kitchen information. Others do not. If a field is missing, do not guess.
Ask the provider or official source whether the plan includes a full kitchen, bathroom layout, storage, laundry, accessibility features, or appliance assumptions.
7. Verify ADU type
Detached ADUs, attached ADUs, garage conversions, and other configurations can have different review needs. A detached backyard cottage may require new utility connections and foundation work. A garage conversion may raise issues around structure, fire separation, parking, or existing conditions.
Make sure the plan type matches your property and goal.
8. Verify site-specific requirements
A pre-approved plan still needs to fit your parcel. Check setbacks, height, lot coverage, easements, trees, drainage, slope, fire access, utility location, and existing structures.
A site plan or professional feasibility review may be needed before you know whether a plan is practical.
9. Verify utility and infrastructure requirements
Water, sewer, electrical, gas, and stormwater requirements can affect cost. Some ADUs may require panel upgrades, trenching, new sewer connections, or utility coordination.
Ask early. Utility surprises can change the project budget.
10. Verify provider terms
If a plan is connected to an architect, designer, prefab company, or builder, ask what is included.
Important questions include:
- Are construction documents included?
- Are structural calculations included?
- Are revisions included?
- Is engineering included?
- Can the plan be modified?
- Who responds to plan check comments?
- Are there licensing restrictions?
Provider terms can be just as important as the design itself.
11. Verify fees and permit costs
Plan cost is only one part of the budget. You may also face permit fees, plan review fees, school fees, utility fees, mapping fees, or provider charges.
When a directory lists fee context, use it as a starting point. Then verify current fees with the city, county, utility, or provider.
12. Verify the information date
Public records can change. A plan that was accepted last year may have updated requirements today. A provider may revise offerings. A city may update its program.
Check when the information was last reviewed and always confirm before making a financial commitment.
Use a directory, then verify directly
The safest ADU research process combines organized online comparison with direct confirmation.
Start with ADU Plan Finder to search pre-approved ADU plans and ADU floor plans by city. Review plan details, provider records, accepted locations, and official source links. Then confirm the current status with the local building department or provider.
This checklist will not replace professional advice, but it can help you ask better questions and avoid common mistakes before you apply for a permit.
Originally published via ADU Plan Finder — a free directory of pre-approved ADU floor plans for US homeowners.
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