Accessory dwelling unit regulations

Design

Standards and guidelines

Your ADU or JADU plans need to comply with the City’s ADU design standards and guidelines. If you use a pre-approved plan, your ADU will comply.

Access doors

ADUs and JADUs must have exterior access independent from the main house.

If the unit is attached to the main house, it can have interior access. The connecting door needs to be 1-hour rated for fire safety.

The ADU design guidelines use the term entry door to mean any new door used to access the unit. Entry doors have specific requirements. These are not considered entry doors:

  • Existing doors
  • Doors that don’t provide entry to the unit
  • Doors to crawl spaces, cabinets, or niches
  • Doors concealing utilities or water heaters

Solar panels

If your ADU will be detached from the main house, you need to add solar panels if the unit is over 1083 square feet.

Utilities

PG&E requires detached and attached ADUs to have electric and gas service separate from the main house. If the ADU is all-electric, you don’t need a gas meter or supply. Contact PG&E for requirements and fees to install separate utility connections.

You do not need a separate water connection.

Architectural features

Architectural features (such as a bay window, clerestory windows, pergola, chimney) need to match the main house. If the main house does not have the feature, you cannot add it to the ADU.

Prefab designs

You can use a prefabricated or manufactured detached ADU if it meets the City’s development and design standards. The new ADU needs to match the architecture of the main house, including:

  • Roof pitch and form
  • Exterior wall material
  • Exterior ornamentation
  • Window and door design

California’s department of Housing and Community Development has approved some prefab ADUs. Some of these may not be subject to Piedmont Design Standards and Guidelines. Contact us if you’re not sure.

Existing ADUs

If you want to make some modifications to the exterior of an existing ADU, you need to apply for a Change to Approved ADU permit. This is a subtype to an ADU permit in our online permitting system.

Parking

Parking requirements

No on-site parking is required.

Impact on future home additions

If you remove on-site parking to build an ADU.

Garages

Converting an existing garage

You can convert an existing garage into an ADU.

If the existing garage is located within the setback area, you can demolish it and construct an ADU in the same footprint, as it has the same dimensions. If it’s more than 800 square feet, it needs to meet the lot coverage, landscape coverage, and floor area ratio limits for your zone.

If you demolish a garage in conjunction with ADU construction or conversion, you do not need to replace the parking.

A JADU can be located within an attached garage, as it's considered part of the existing single-family dwelling.

Replacing your garage and adding an ADU

If you want to replace your garage and add an ADU, the new construction needs to meet the ADU standards for building height and setbacks. If the ADU is more than 800 square feet, it needs to meet the lot coverage, landscape coverage, and floor area ratio limits for your zone.

The new garage (or living space not included in the ADU) needs to meet the development standards for your property’s zoning. You will need design review approval.

Garage door removal

If you remove a garage door for an ADU conversion, a 3-foot wide landscape strip may be required along the ADU wall where the door was located.

Non-conforming uses

Your house or ADU may be considered non-conforming if:

  • It met the City’s regulations when it was built
  • But does not meet our current regulations

Most homes in Piedmont were built before the City’s current design standards. If your house exceeds current zoning standards, you can still add an ADU.

  • If the ADU is 800 square feet and less, it’s exempt from lot coverage, landscape coverage, and floor area limits.
  • If the ADU is larger than that, it must meet lot coverage, landscape coverage, and floor area ratio limits (unless it is an existing habitable space conversion).

The ADU structure does not need a design review permit, but you will need one if you want to make exterior changes to the main house.

Existing ADU

If you have an existing unit on your property that exceeds the size limits of the current regulations, you can make changes to the exterior as long as:

  • The unit meets the current building code
  • The changes meet our design standards and guidelines
  • You don’t make the unit bigger, move its location, or add more bedrooms
  • You don’t increase the building’s footprint or reduce the yard space

Pool house

If a pool house has the same features as an ADU, you need an ADU permit for it to be used for housing. If you do not have an ADU permit, it cannot be occupied.

This also applies to a cottage, basement, or attic.

Zoning code

Accessory and junior dwelling units need to comply with Piedmont’s zoning regulations, City Code division 17.38.

Building code

Accessory and junior dwelling units need to comply with State and local building code regulations.

Fire safety

Visibility

All ADU addresses must be visible from the street.

Driveways and access

  • Walkways/Driveways leading to the ADU must be permanent, at least 36 inches wide, and well lit.
  • Width of driveway needed for public safety vehicular access should be 12 feet minimum and 16 feet where it curves.
  • Fire sprinklers needed if ADU is more than 150 feet from the access road.

Vegetation and utilities

  • The first 30 feet from the building needs to be clear of dead branches and bushes and firewood.
  • Ensure enough defensible space.
  • Utility (shut offs) clearly marked.

Exterior

If new construction, you need to use WUI rated fire resistive construction material.

Home ignition zone considerations

Simple steps from roof to foundation to make a home safer from embers and radiant heat:

  • Clean roofs and gutters of dead leaves, debris and pine needles that could catch embers.
  • Replace or repair any loose or missing shingles or roof tiles to prevent ember penetration.
  • Reduce embers that could pass through vents in the eaves by installing 1/8 inch metal mesh screening.
  • Clean debris from exterior attic vents and install 1/8 inch metal mesh screening to reduce embers.
  • Repair or replace damaged or loose window screens and any broken windows.
  • Screen or box-in areas below patios and decks with wire mesh to prevent debris and combustible materials from accumulating.
  • Move any flammable material away from wall exteriors-mulch, flammable plants, leaves and needles, firewood piles– anything that can burn. Remove anything stored underneath decks or porches.