San Mateo County · California
Atherton ADU guide: local rules, permits & property planning
Atherton’s fee waivers make it especially important to separate Town charges from fire, water and sewer charges. The responsible utility district is part of the budget, even when a Town fee is waived.
Local planning guide · Reviewed October 2, 2026
What matters for an ADU in Atherton
Permitting authority: Town of Atherton — ADUs
Official local guidanceLocal rules and design checks
| Topic | Local guidance |
|---|---|
| JADU scale | The Town describes a JADU as no larger than 500 square feet within the qualifying home. |
| Accessory conversions | For an existing legal accessory building, establish the permitted footprint and applicable safety requirements before proposing a conversion. |
| Utility jurisdiction | The Town points owners to Menlo Fire, Cal Water and the applicable sanitary district for outside requirements. |
Selected local requirements, not a complete zoning determination. Confirm the current rules for your address with the responsible agency.
Fees and budget checks
Atherton says it waives several ADU permit fees, but outside-agency charges remain. Its page identifies Menlo Fire, Cal Water, Fair Oaks Sanitary and West Bay Sanitary, and notes that charges can include initial and recurring amounts.
Atherton fee-waiver and agency guidanceHow to start the permit process
Confirm the ADU or conversion path with Town Planning and Building, then obtain the separate fire and utility requirements for the address. Record which agency charges are covered in each estimate.
Municipal program
Atherton ADU fee-waiver guidance
The Town publishes a local fee-waiver explanation and an outside-agency list. The program does not establish a zero-cost permit package.
View the original sourceAtherton ADU questions
- Does Atherton’s waiver eliminate utility charges?
- No. Request estimates directly from the serving water and sanitary providers and fire agency.
- Is an ADU legalization program already available?
- The reviewed Town page describes work toward an amnesty program. Ask the Town about its current status before relying on it.
Sources for this guide
Local sources reviewed October 2, 2026. Historical examples retain their stated dates. Contact ADU California to confirm project availability; this guide does not establish an office location or property approval.
A useful first review
Separate what is available from what still needs verification.
01
Confirm the property
Start with a complete address and review the available parcel, building, and map context.
02
Identify the unknowns
Keep missing setbacks, easements, utilities, access, hazards, and local requirements visible.
03
Choose the next review
Use the preliminary result to prepare a focused conversation with the required professionals and agencies.
Explore project types
Compare the scope before choosing a solution.
These pages explain the questions each project type introduces. They do not assert that a particular scope is permitted or suitable for your address.
Compare planning footprints
See common ADU sizes before choosing a design.
These model pages are planning references only. They are not a statement that a particular size is allowed or buildable at a Atherton address.
California directory
Explore more city guides.
The next useful action
Put your address at the center of the conversation.
The online review is preliminary and is not a permit decision, survey, engineering opinion, construction document, final price, or guaranteed schedule.