Planning Your ADU

5 Stages of ADU Planning


There are many ADU plans available. Some homeowners may choose to connect with an architect, but many find there is already a floor plan design that would work perfectly. The links below can help you find a plan that works for you.

Site Plan

You must submit a site plan in order to obtain a building permit. Site plans need to be drawn to scale and include the following information:

Include drainage flow, grade elevations and provide sizes of all structures and setbacks from structures to the property lines.

Indicate size of footings, sill plates, reinforcements, anchor bolts, washers, and slope/grade.

Indicate size of footings, sill plates, reinforcements, anchor bolts, washers, and slope/grade.

Indicate the new areas, door sizes, window sizes, headers, electrical outlets, light switches, light fixtures, FAU registers and plumbing fixtures. (Existing floor plan to be included)

Indicate type of roof, pitch, ridges, rafter spans, valleys, hips, flashings, overhangs, drainage and show all lumber sizes.

Energy Compliance Forms


There are many ways to finance your ADU. Of course, credit scores, existing debt, and your existing equity will impact your options.

You will also be assessed regarding the amount of value your ADU adds to your property value, based on comparable sales in your area.

Consider an Affordable Housing Covenant with City of Claremont


Before you start building a second unit, you will need a building permit and other approvals from the city of Claremont. The city will need detailed plans of your ADU project that must be drawn to scale. The city needs to determine if your project conforms to local zoning regulations, and needs to make sure that the design is safe and up to code.

Helpful Links

Accessory Second Unit Application

Building Permit Worksheet/Application [PDF]

Residential Submittal Checklist [PDF]

Permit Worksheet [PDF]


Select contractor by soliciting bids. Be sure to choose a licensed contractor. ADU construction costs typically range from $60,000 to $100,000. 

Be prepared: there might be some unforeseen complications related to construction, that could cost extra. These common issues include:

  • Building a proper foundation, which can happen with older garages that are built on a concrete slab

  • Reinforcing insufficient framing to give the dwelling stability

  • Extra piping and digging to appropriately connect your new kitchen sink, toilet and/or shower to the sewer system