What is an Accessory Dwelling Unit?
An accessory dwelling unit (ADU), sometimes referred to as a granny flat, in-law unit, second unit, backyard cottage, or backyard dwelling, is a secondary residential unit added to the same property as a primary home. ADUs come in many forms and sizes and always include a kitchen, bathroom facilities, and a sleeping area.
Why build an ADU?
- Passive Income (rental property)
- Increase your property value
- Accommodating guests
- Private office space
- Home gym area
- A home for senior family members
- A home for recent college grad
- On-site temporary dwelling during construction
- Create jobs
- Increase housing production
- Decreasing commuting times for local workers and alleviating traffic
A view towards an ADU project currently on the boards, that houses a living space and roof deck above an existing 3-car garage. This ADU measures 1,199 SF in space, just 1 SF shy of the maximum allowed.
What are the limitations and parameters of new ADUs?
- The minimum floor area is 220 SF
- The maximum floor area is 1,200 SF or up to 50% of existing dwelling if attached.
- Second units in certain areas may require a conditional use permit if the proposed unit is located within a Very High Fire Hazard Severity Zone, or within an area not served by a public sewer system or water system.
- Second units are prohibited on hillsides with a slope greater than 25%
- While local governments may impose standards on ADUs, these standards shall not include minimum lot size requirements. Further, lot coverage requirements cannot preclude the creation of a statewide exemption ADU (800 SF ADU with height limitation of 16 ft. and 4 ft. side and rear yard setbacks. (Although the application of CA Coastal Act of 1976 will supersede Los Angeles Municipal Code)
- Parking for a newly constructed ADU is not required when it is located within one-half mile walking distance of a public transit
- New ADUs may require a fire sprinkler system. If the Primary Residence has fire sprinklers, then the new ADU will require them. Fire sprinklers are not required if the Primary residence does not currently have them.
- Detached ADUs may not be more than 2 stories tall.
- Utility easements may impact buildable area
A overhead view showing how a backyard ADU garage conversion can be visually integrated with the primary residence.
Cost: $350/SF and up
- A newly constructed freestanding rectangular box; consider two-stories, will be relatively lower cost
- A renovation or conversion in place of an older detached garage in poor condition with architectural ambition (i.e. $150K for 350 SF garage conversion) will be relatively higher cost
- Consider additional cost for utility connections, underpinned/enhanced footings, insulation (T24 compliance), etc.
Architectural Design Fees
Below are the standard project phases with typical fee percentage breakdowns. Design fees range from 15 – 20% +/- of the overall construction budget for small projects, engineers fees are additional.
- Schematic Design 25% (estimated portion of overall architectural services, fees)
- Design Development 15%
- Construction Documents 40%
- Bidding/Negotiation 5%
- Construction Administration 15%
Schedule
- Design time: 1 month (prefab., standard plans) to 3+ months (custom “small home”); includes contribution of coordinated input from consultants including structural engineers, civil engineer for LID, drainage, etc., Title 24 analysis, MEP if required.
- Permitting time: Assume 6 months; longer if Coastal Commission, Methane, LID, DWP Encroachment Permit process
- Construction time: 4-6 months for main house interior work only, 6-12 months for attached or free-standing new construction
- Overall project duration: approx. 1 year minimum +
Overhead views of our Venice ADU project that maximizes the allowable square footage
