Number of ADUs Allowed in Hawthorne
- Maximum size: 1,200 sq ft (detached or attached, or 50% of the size of the main dwelling)
- Side/rear setbacks: 4 feet
- Two story: Yes, for both attached and detached ADUs
- Building separation: 6 feet
- Soils Report: Possibly, especially in areas with grading or on hillsides
- Building Verification Survey: Yes
- Coastal permit (in some areas): N/A
- Stormwater Mitigation: Yes
Number of ADUs Allowed in Hawthorne
Up to one ADU and one JADU can be built on a single-family lot in Hawthorne.
Multifamily property owners in Hawthorne may convert existing uninhabitable space into at least one ADU, and additional ADUs not to exceed a maximum number equal to 25% of the existing units. Ergo:
- From 2 to 7 units, you could convert existing uninhabitable space into one ADU
- From 8 to 11 units up to 2 ADUs
- From 12 to 15 units up to 3 ADUs
- And so on.
No more than two detached ADUs may be constructed on a multifamily lot in Hawthorne.
ADU Hawthorne – Size & Building Constraints
A detatched ADU in Hawthorne can be up to 1,200 square feet.
An attached ADU in Hawthorne can be up to 1,200 square feet, or 50% of the size of the primary dwelling unit, whichever is smaller.
An ADU in Hawthorne may be no more than 16 feet high. If the ADU is built over a garage, it may reach a height of up to 25 feet.
With most ADUs limited in height to 16 feet unless they are a single story above a garage, a two-story ADU will usually not be permitted in Hawthorne due to height restrictions.
No, ADUs cannot be stacked one on top of each other on two stories in Hawthorne.
Two ADUs are only permitted on multifamily property. Hawthorne regulations do not specify the configurations, and two attached ADUs may be permitted on a case-by-case basis.
No, a JADU is defined as an ADU converted from existing space within the main structure of the primary dwelling unit. As such, it cannot be attached to an ADU.
Generally roof decks would be permitted on an ADU, but must meet the height restrictions for the zone. Roof decks cannot encroach into the required setbacks. As a rule of thumb, railings and access staircases above 42″ need to be included in height calculations.
In Hawthorne the ADU must match the architectural design of the proposed or existing structure. This includes using the same exterior material, roof material, color, and architectural details of the main dwelling unit.
ADU Setbacks in Hawthorne
ADUs behind the primary dwelling unit in Hawthorne require a minimum of 4-foot side and rear setbacks.
Hawthorne does not specify specific building separation for ADUs from the primary dwelling unit or other structures. Enough separation must be maintained to comply with fire codes and reduce the risk of fires spreading from one building to another. Separation requirements will be determined in the planning stage.
ADUs are generally not allowed in the front yard in Hawthorne.
ADU Setbacks in Hawthorne
No, the City of Hawthorne encourages online submission of plans to the Hawthorne Planning Department via theHawthrone Citizen Self Service Portal.
Hawthrone may require a soils report for ADU permitting to make sure the soil can support the new structure, especially if the ADU will be located on a hillside, an area with significant grading, or if there are special foundation requirements.
Hawthorne specifies no specific requirements for “green” space or permeable surface on your landscaping when constructing an ADU. However, green space and permeable surface may become an issue in the approval process if the ADU covers a significant portion of the lot.
The plan check requires a review by the Planning Department for zoning, building standards, and safety compliance. The process takes approximately 4-5 weeks.
Parking for Hawthorne ADU
Hawthorne requires one new parking space be added per new ADU. However, if the property is within one mile of a public transit stop and/or if the ADU or JADU in question is being converted from existing space within the main dwelling unit, the ADU is exempt from the requirement of extra parking.
If a parking space must be added, it can be included on the driveway or any setback areas, and it may be configured as tandem parking.
Additional Requirements in Hawthorne
Per Title 24 of the California Energy Code, solar panels of appropriate size and capacity are mandatory on new-construction ADUs. ADUs built from converted existing structures are exempt, as may be ADUs located under significant shading. Smaller ADUs may be subject to reduced or modified solar panel requirements.
An ADU is not required to have a separate water or electrical meter. You can opt for the ADU to share service with the main dwelling unit. However, you can request separate water or electrical meters from the City of Hawthorne.
Hawthorne does not automatically assign a new ADU its own address. However, it may assign the ADU a new address if it is intended for rental or independent occupancy. The ADU will usually get a “½” designation — for example, an ADU located behind 1234 Pine Street would have the address “1234½ Pine Street.”
Low Impact Development (LID) is an approach to land development or redevelopment that seeks to preserve and conserve onsite water quality and natural features, with minimal detrimental effect to local waterways and ecosystems. Hawthorne may require LID fees for larger ADUs.
An ADU may not be used as an Airbnb or short-term rental in Hawthorne.
Per the Costa-Hawkins Act of 1995, Hawthorne does not impose rent control on dwellings constructed after February 1, 1995. This means most new-build ADUs are exempt. However, if the primary dwelling unit is subject to rent control, it might apply to the ADU as well.
While encouraging the use of electric appliances for efficiency and sustainability, Hawthorne does not prohibit gas appliances in new ADUs as long as all relevant installation and safety standards are met.
In Hawthorne you are only required to install sprinklers in a new ADU if the primary dwelling unit has them as well. You may also be required to install them if the ADU is located within a special fire hazard zone.
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