Garage Conversion

We will convert your garage into your dream living space!

Are you thinking about converting your garage? Having the the idea of turning it into an extra bedroom, office, playroom, gym, or even an in-law unit.

Since the foundation, walls and roof are already in place in many houses, a well-planned garage conversion can create a space that will match well with the existing house.


Converting your garage into a living space adds value to your property. This added value comes from the overall price of the property or from the potential to rent out the area.

We’ll make sure that every inch of space is maximized, and you’ll be able to enjoy your new addition for years to come.


What is required to convert a garage into a residential dwelling unit?

The garage needs to comply with the Building Code and Fire Code, including:
  • Walls and foundation with structural integrity
  • Utilities (electricity, water, sewage)
  • HVAC – A common solution is to use a ductless heat pump (mini-split system) that is separate from the existing HVAC system of the main residence.
  • Insulation
An individual project’s compliance with the local energy and building code will determine whether the garage door must be replaced.

What are common issues when converting a garage?

Complying with the Building Code Additions or alterations to existing structures, and changes from non-residential to residential use must comply with Building Code requirements for new construction. Common upgrades or required changes may include:
  • Altering the existing roof structure.
  • Performing structural upgrades when replacing a garage door and/or adding window and door openings.
  • Creating a moisture barrier between the slab and the flooring.
  • Underpinning the foundation and/or upgrading the existing slab.
  • Ensuring adequate insulation and meeting CA Title 24 energy code.
Determining whether the existing garage has structural integrity A structural engineer may be required to examine the garage. If the foundation and walls of the structure need to be replaced or repaired, the cost of the project will increase significantly. In some cases, it may make sense to tear down the structure and rebuild a new one with the same dimensions on the same footprint. Meeting fire safety requirements
  • Between the garage and the property line.
  • Between the garage and a nearby dwelling.
Creating a sound barrier between the main house and the ADU if they share a wall Determining a solution for the relocation of the water heater, washer/dryer, and storage in an attached garage Possible solutions include:
  • Creating a small utility room.
  • Using a tankless water heater; some models can be installed outdoors.
  • Using a stacked washer/dryer or all-in-one unit.
  • Building a backyard shed for additional storage.
Meeting the increased electricity requirements. Load calculations need to be performed to determine if the existing electrical service is sufficient. Frequently, a new main electrical service with greater capacity is required. In addition, it is common to add a subpanel for the ADU.   Meeting increased requirements for other utilities. The property’s main water, sewer and gas lines might need to be upgraded to a larger diameter line to accommodate the additional demand and meet current building code requirements. Water and Sewer Districts may not require a separate service connection (consistent with CA Govt Code section 65852.2(f)(4)). Electric and Gas corporations may require a separate service for garages.

How much do garage conversions cost in comparison to other ADU types?

If the garage is in sound condition, a garage conversion ADU typically costs less than a new detached or extension ADUs. However, the cost of a garage conversion varies greatly depending on following factors:
  • Size of the ADU.
  • Cost of construction in the geographic location.
  • Upgrading the garage to meet the current building code.
  • Structural improvements to the garage.
  • Cost to upgrade utilities (water, electricity, sewer line) in the garage.
  • Cost of compliance with the local Fire Access Requirement (distance from the face of the curb to the back of a freestanding ADU).
  • Type of ceiling (vaulted or flat).
While the answer widely depends on a home’s location, geographic topography, and existing conditions, the starting price will probably to be upwards of $100,000 for a garage conversion. Local jurisdictions have begun developing their own ADU calculators. We suggest using these (if prepared by nearby jurisdictions) to help estimate the costs. Examples can be found here for Napa Sonoma ADU Center and the County of San Mateo.


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Call us at (650) 241-5384 or send us an email at [email protected] or