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Fire Sprinkler Requirements for Additions to Existing, Non-Sprinklered Dwellings

TECHNICAL BULLETIN
RESD-3-1
March 2025

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IN THIS BULLETIN:

The purpose of this Technical Bulletin is to establish the City of San Diego’s interpretation for requiring fire sprinkler systems in additions and alterations to existing one- and two-family dwellings and townhouses that do not have an existing fire sprinkler system installed. For the purpose of this Technical Bulletin, dwelling units are defined in the California Residential Code (CRC) and the floor area of the unit must include all habitable spaces and all non-habitable spaces such as garages and storage areas. All new dwelling units are required by CRC Section R313 to be provided with fire sprinkler protection unless exempted in Section II below.

Sprinkler Protection For Existing Dwelling Units

Installation of a fire sprinkler system in existing dwelling units shall be required for the following cases:

  1. New Dwelling Unit 

    When a new dwelling unit (detached or attached) is added on the same lot with an existing dwelling unit, fire sprinkler protection must be provided for the new dwelling unit.

  2. Existing Dwelling Unit Additions

    When the floor area of an existing dwelling unit is increased, a fire sprinkler system shall be installed throughout the entire dwelling (existing areas and new addition areas) when both of the conditions occur:

    1. The total floor area of the dwelling (existing plus the new addition) is greater than 3,600 sq. ft. and
    2. The floor area of the addition exceeds 50% of the floor area of the existing dwelling.

Exceptions to Sprinkler Protection

Installation of a fire sprinkler system shall not be required for the following cases:

  1. Existing Dwelling Unit Alterations

    When an existing dwelling unit is altered to create two separate dwelling units with no change in the building’s total floor area, sprinklers are not required.

  2. New Guest Quarters

    New guest quarters, as defined in LDC Section §141.0307, are not considered new dwelling units. Therefore, a guest quarter added to an existing dwelling unit, either attached or detached does not require sprinkler protection.

  3. Accessory Dwelling Units/Junior Accessory Dwelling Units

    See Information Bulletin 400 and Technical Bulletin RESD-3-4 for sprinkler requirements for Accessory Dwelling Units and Junior Accessory Dwelling Units.

References