Following a conversation with a Planner in Step 1, ask for a “Plans Examiner” to assist you with questions you might have regarding building code requirements. The plans examiner will be able to go over building code issues with you.
There are two basic areas of code to address during the conversion of a garage to living space. These are discussed below.
Fire and Life Safety Code Requirements
When converting a garage to living space, the code requires provisions for occupant health and safety, such as emergency egress from sleeping areas, smoke and carbon monoxide alarms, minimum headroom, stair rise and run, landings at stairs and doors, ventilation, lighting and heating of habitable spaces, etc. Most likely, a minimum amount of modifications will be required to convert the garage to a safe living space.
Energy Code Requirements
The Washington State Energy Code (WSEC) requires that any previously unheated space that is being converted to heated space shall fully comply with current energy code requirements such as attic insulation and venting, wall and floor insulation, and energy code compliant windows and exterior doors.
Here are the specifics:
- Attic insulation: Minimum R-49 for attics (possibly R-38 for single rafter framing with no attic space). An attic access panel (minimum 22” x 30”) will be required to access the attic area. Since the attic area will now have heated space below the ceiling, it will also need to be ventilated.
- Wall insulation: Minimum exterior wall insulation of the heated space shall be R-21. If existing walls consist of 2x4 framing, they will need either rigid or high-density insulation, or be furred out to accommodate R-21 insulation. The existing garage door(s) will need to be removed and replaced with a framed wall that can accommodate R-21 insulation.
- Windows and exterior doors: Fenestrations (openings in an exterior wall) shall have a maximum U-factor of 0.30. (The lower the U-factor, the greater a window or door's resistance to heat flow and the better its insulating properties.)
- Floor insulation: The existing concrete slab serving as the garage floor does not provide adequate insulation for a heated space. Bringing the space up to current code will require modifications, and can be achieved in multiple ways. Some common solutions are listed below.
- Provide R-10 rigid insulation on top of the slab. Flooring material could then be placed atop the rigid insulation; or
- Install wood floor joists over the slab and add loose R-30 insulation between the slab and floor sheathing or covering; or
- Provide R-10 insulation on the exterior of the foundation and stem wall of the garage area for a total depth of 24" (or to the top of a footing, whichever is less).
No matter how floor insulation is accomplished, thermal breaks must also be provided around the perimeter of the floor and foundation stem wall, where heated space is adjacent to unheated space
Note: If raising of the floor occurs, code requirements for stairs, landings, doors, and headroom must still be met, along with underfloor ventilation and access where required.
- Energy credits: When an addition of heated space is made to an existing house, a certain number of energy credits shall be obtained. There are several methods of obtaining credits, and the chosen method must be indicated on the plans.
The required number of credits and ways of obtaining credits can be found in the WSEC, R406.2.