What You Should Know Before Converting a Garage in California

Have you ever wondered if your underused garage could serve a better purpose than storing clutter? Whether you’re after rental income, need space for an adult child or an aging parent, or want to add resale value to your home, Accessory Dwelling Units (ADUs) make efficient use of wasted garage space. If you live in California, there has never been a better time to convert your garage into a living space. Previously stringent permitting procedures and burdensome code requirements have been lifted by Senate Bill 1069 (SB-1069), and most single-family homes in the State now qualify for such a conversion.

Despite an easier approval process and fewer limitations, converting a garage into a living space still presents a challenge to the average homeowner. State and local ordinances govern the six factors that must be considered before applying for a new permit. They are as follows: floor area, setbacks, replacement parking, new foundations, space conditioning, and life safety.

1. Floor Area & Setbacks

Whereas new ADUs must be constructed a certain distance away from the property line, there are no setback limitations on existing garages undergoing a conversion. The floor area of an attached ADU can reach up to 50% of the existing living area, or a maximum of 1,200 ft², while detached ADUs are limited to 1,200 ft².

2. Parking

Prior to SB-1069, off-street parking had to be provided for spaces lost to the conversion. The new bill made away with this requirement, given that the converted unit meets any of the following criteria:

  • It is within a half-mile radius from a public transit system
  • It is located in an architecturally and historically significant district
  • On-street parking permits are required but not offered to the occupant of the new unit
  • A car share vehicle can be found within one block of the new unit

For units failing to meet all the above criteria, replacement parking spaces will have to be accommodated on the property.

3. Foundations & Flooring

Foundation and flooring requirements will vary from project to project. That being said, here are a few common ones to consider:

  • New infill at the existing garage door opening
  • A stem wall for water separation
  • R-19 insulation for raised wooden floors
  • R-7 slab perimeter insulation in Climate Zone 1

An engineering professional will be able to advise on the most practical and economical approach to foundations and flooring.

4. Space Conditioning

Perhaps the greatest challenge of a garage conversion is the conditioning of previously unoccupied space. Converted garages must comply with Building Energy Efficiency Standards for wall assemblies, roofs, ceilings, floors, glazing, and mechanical systems.

The existing walls of a converted garage must have cavity insulation of R-15 for 2 x 4 framing, and R-19 for 2 x 6 framing. New walls that replace garage doors must conform to the same, provided they are on one plane with the existing walls.

The roof of an ADU less than 700 ft² in floor area must have insulation with a thermal resistance of R-22. Units larger than 700 ft² have several compliant options, with requirements varying by Climate Zone. For example, in Los Angeles and in the Bay Area, ceiling insulation of R-30 and a radiant barrier are required, whereas, in Inyo County, ceiling insulation of R-38 is sufficient.

All glazing in a converted garage must meet standards for resistance to heat caused by sunlight (Solar Heat Gain Coefficient), as well as the rate of heat loss (U-Factor). Constraints to the amount of glazing are determined by the floor area of the conversion. Please refer to the table below for a summary of fenestration requirements for an ADU.

It should be noted that Climate Zones 1, 3 and 5 are exempt rom the west-facing limitation and Solar Heat Gain Coefficient requirement.

5. Mechanical Systems

Conditioning systems will probably be installed to service the newly converted garage. Here are a few things to consider:

  • Return air shall not be shared with other dwelling units.
  • The HVAC system must meet the requirements that apply to new buildings.
  • Conversions larger than 1,000 ft² require whole-building airflow.
  • If an existing dwelling does not have a natural gas connection, an electric water heater can be installed to serve the ADU.
  • When converting the garage into a bedroom, existing gas-fired water heaters and furnaces must be removed from the space or enclosed.

6. Life Safety

Most ADUs must come equipped with passive fire protection measures and a means of escape or the occupants. Attached garages undergoing a conversion will typically have to include a fire separation at the connection to the existing dwelling, but unlike new homes, they only need an automated sprinkler system if the existing dwelling already has one.

Permitting & Construction

Once all of the factors relating to construction have been considered, it is time to get the permit application ready. Typically, a city’s building department will need at least the following documents:

  • Permit Application Form
  • Title 24 Compliance Forms
  • Site Plan Drawings and Vicinity Map
  • Structural Drawings
  • Floor Plan Drawings
  • Elevations Drawings
  • Roof Framing Plan
  • Mechanical and Electrical Drawings

The plan review process may go through one or two revision cycles, and can last anywhere between four to six weeks. Once the building department issues a permit, construction can begin.

Do It Yourself or Call the Pros?

Some aspects of garage conversion have become more layman-friendly in recent years, yet the challenges are easy to underestimate. An owner-builder is likely to make mistakes that can delay the project and result in massive cost overruns. If you want your garage conversion to stay on schedule and on budget, please consider hiring a qualified and experienced engineer to guide you through the process.

Our team of seasoned professionals has the expertise to save you time and money during all phases of a garage conversion and to ensure seamless project delivery. Aside from garage conversions, our team can also assist with garage renovations and garage extensions. If you are ready to convert your underused garage into valuable living space, our engineers are standing by to lend a hand. Call us at (888) 311-3015 for a FREE consultation and quote.

Sources:
[1] https://citylab.ucla.edu/adu-guidebook/

[2] http://www.cityofvista.com/home/showdocument?id=350

[3] https://www.energy.ca.gov/2015publications/CEC-400-2015-037/CEC-400-2015-037-CMF.pdf

[4] https://energycodeace.com/download/24214/file_path/.../Decoding.ADUs.Handout

[5] https://fremont.gov/DocumentCenter/View/7182/COMBUSTION-RETURN-AIR-SEPARATION

[6] http://www.hcd.ca.gov/policy-research/docs/Fire-Marshal-IB.pdf

[7] https://la.curbed.com/2017/1/9/14219298/granny-flats-new-rules-state-back-house-in-law

[8] https://www.latimes.com/politics/essential/la-pol-sac-essential-politics-updates-yes-in-your-backyard-legislature-says-1472608442-htmlstory.html

[9] https://www.pge.com/myhome/edusafety/workshopstraining/pec/toolbox/arch/climate/index.shtml

[10] https://www.sandiego.gov/sites/default/files/dsdib142.pdf