Room Additions
Room Addition Defined
The California Building code defines an addition as an extension or increase in floor area or height of a building or structure. The California Energy Commission defines a residential room addition, in part, as an increase of conditioned space to an existing conditioned building.

A conditioned space is enclosed space that is provided with heating and cooling for the provisions of human comfort by transporting air through ducts and plenums, or by heated or cooled surfaces whose output is greater than 10 BTU per hour per square foot of floor area.
Zoning Requirements
Before a building permit can be issued by the Building and Safety Division, information concerning zoning regulations must be obtained from the Planning Services Division. Each property within the County is part of a designated zoning district. The zoning district specifies the permitted land uses, such as residential, commercial, or industrial and the minimum distances or set back from the property lines for buildings, accessory structures, and fences, as well as maximum height restrictions.

When you apply for a building permit, the application will automatically be routed to the Planning Division for review.

You are encouraged to contact the Planning Division at (707) 784-6765 before you finalize your plans to make sure that the addition meets minimum zoning requirements and does not encroach on easements or required side, front, or rear yard areas.
Required Drawings
Minimum Plan Checklist
The following may be a deferred submittal:
  • Fire Sprinkler Plans
  • Roof Truss Calculations

Deferred submittals shall be submitted to the project engineer who shall review the documents and provide a written statement on the documents informing the Building and Safety Division that they have reviewed the documents and that they have found them to be in complaince with the general design of the building. The engineer of record shall then provide their signature after the statement and the documents can then be subbmitted to the Building & Safety Division for review and approval.

Submit Four (4) sets of the following drawings are required, if applicable:

Sheet Sizes/Scale - 8 1/2"x 11" or larger plan sheets are required. Plot plan scale to be sized to show overall property, if less than 1/8"/ft. scale, an enlargement of the building site to at least 1/8" scale is required. Detail is to be at least 1/2" scale, all other views a minimum 1/4" scale. Number each sheet, example: sheet 1 of 8, 2 of 8, etc.

Site Plan - This plan is a view of the entire property. Clearly show and dimension to scale all property lines, easements, setbacks, roads, drainage away from the building, existing structures, proposed structures, retaining walls, water well(s), septic system(s), LP tank(s), streams, north arrow, scale, owner name, name of person preparing plans and project address. Additions and/or areas of remodel shall be shaded and/or cross hatched in relation to overall building.  Sample Site Plan

Foundation Plan - Provide layout of foundation to scale. Show perimeter and interior bearing footings, slab, piers, stairs and fireplaces. Show details of each foundation section indicating size, reinforcement and sill plate attachment.

Floor Framing Plan - Provide sheathing thickness, size, grade, spacing and layout of all framing members. Provide wet stamped and signed manufactured truss plan(s) and layout if applicable. Show details of all connections, components, attachments, anchorage, etc.

Roof Framing Plan - Provide sheathing thickness, size, grade, spacing and layout of all framing members. Provide wet stamped and signed manufactured truss plan(s) and layout if applicable. Show details of all connections, components, attachments, anchorage, etc.

Floor Plan - Show all interior and exterior walls, doors, windows, stairways, fireplaces, closets, counters, attic/underfloor access, plumbing fixtures (water heaters, toilets, showers, tubs, sinks, dishwashers, clothes washer/dryer, stove top, oven, etc.). Show location and layout of HVAC system. Show all electrical outlets, switches, lights, smoke detectors and electric panel(s). For additions and alterations, graphically show new, existing, and removed components. Each room or space shall be labeled to reflect its intended use.

Elevations - Show the elevations being changed. Show all exterior features such as the style of the building, doors, windows, decks, finishes, patios, chimneys, trims, etc.

Energy Forms - Energy forms shall be submitted as an entire package for any alteration or addition to the envelope, lighting, or mechanical system of a building or structure regulated for energy efficiency by the California Energy Commission. This includes change-outs of existing mechanical systems. For residential projects the CF-1r's and CF-4R's shall be made a permanent part of the plans. Forms shall be signed by the owner and designer.

Soils Report -and analysis with foundation design criteria (foundation type, soil load limits, etc.) may be required for all new structures.

A hand out is available through the Building Division office that may assist in plan preparation. This hand out includes samples of the plans listed above with examples of the type of information and degree of detailing required for plan submittal.
Non-Structural Considerations

Garages - If the addition forms a common wall between the garage and the addition, the wall must be constructed with one-hour fire resistive materials on the garage side extending from the garage slab to the roof sheathing. Door openings from the garage into the dwelling are protected with a solid core, self-closing, tight fitting, one and three eighths inch minimum thickness door. Electrical wiring, plastic plumbing piping and ducts penetrating the firewall within the garage must be encased in metal that has the equivalent thickness of 26 GA galvanized steel.

Room Sizes: - Every dwelling unit shall have at least one habitable room that shall have not less than 120 square feet of gross floor area. 


  1. Kitchens   

Other habitable rooms shall have a floor area of not less than 70 square feet.

Ceiling Height: - Habitable rooms shall have a ceiling height of not less than 7 feet in any horizontal dimension.


  1. Kitchens   

Windows: - All habitable rooms need skylights or windows for natural light. The minimum window area is not less than 8% of the floor area of such rooms. If the window serves as an emergency egress for a bedroom, it must have an opening to the exterior of the building of at least 5.7 square feet with a minimum clear opening width of 20 inches, a clear opening height of not less than 24 inches, and a finished sill height not more than 44 inches above the floor.

Ventilation: - Natural ventilation shall be through windows, doors, louvers or other approved openings to the outdoor air. Such openings shall be provided with ready access or shall otherwise be readily controllable by the building occupants. The minimum openable area to the outdoorsd shall be 4% of the floor area being ventilated.

Smoke Detectors: - Smoke detectors are required to be installed when the value of the addition exceeds $1,000.00, or when one or more sleeping rooms are added. The smoke detectors may be solely battery-operated in buildings which undergo alterations, repairs or additions. They are installed in each sleeping room and at a central location in a corridor giving access to sleeping areas. If the addition is a 2 story, a smoke detector is required at each story, and if the sleeping rooms are on the upper level, the detector is placed at the center of the ceiling directly above the stairway.

Carbon Monoxide Detectors: - For new construction an approved carbon monoxide alarm shall be installed in dwelling units and in sleeping units within which fuel-burning appliances are installed and in dwelling units that have attached garages. In new construction the alarm shall recieve its primary power form the building wiring and shall be equipped with a battery back-up.

        Exception: - In existing dwelling units a carbon monoxide alarm is permitted to be solely battery operated where alterations or repairs do not result in the removal of wall and ceiling finishes.

Carbon Monoxide alarms in new construction shall be interconnected.  A carbon monoxide alarm shall be installed outside of each separate dwelling unit sleeping area and in the immediate vicinity of the bedroom(s) and on every level of a dwelling unit including basements.

In existing dwelling units where a permit is required for alterations, repairs, or additions exceeding $1,000, existing dwellings or sleeping units that have attached garages or fuel burning appliances shall be provided with a carbon monoxide alarm.

State Building Energy Efficiency Standards
In accordance with the California Code of Regulations Title 24, all new construction must comply with the building energy efficiency standards in effect on the date a building permit application is filed. The standards apply to any addition that increases the conditioned area of a building.

Luminaires recessed in insulated ceilings must meet three requirements (150(k)(5)):

·         They must be rated for direct insulation contact (IC).

·         They must be certified as airtight construction.

·         They must have a sealed gasket or caulking between the housing and ceiling to prevent flow of
      heated or cooled air out of living areas and into the ceiling cavity.


Provide gaskets on all interior outlets that are located on an exterior wall. (117)


Provide a gasket/ insulation on all interior attic/under-floor accesses.  (117)


Insulate the first 5’ of hot/cold water lines from the water heater. (150(j)(2))


Dwellings are to meet California Energy Commission (CEC) standards.
Provide compliance documentation and mandatory  measures.


Air infiltration, insulation, space heating, space cooling, water heating, orientation, windows, etc,
shall meet California 
Energy Commission (C.E.C.) standards.


Weatherproofing of exterior surfaces above and below grade is required (CBC 1402). For air
infiltration mandatory 
requirements, see Building Code.

Summary of 2008 Residential Lighting Standards (150(k)) 


General Requirements
(All Rooms/Areas)
  • Unless allowed under "alternate options," all hardwired lights must be fluorescent and contain conventional medium screw based sockets.
  • Eltronic ballast for fluorescent lights rated 13 watts or more.
  • Swithc fluorescent lights separate from non-fluorescent lights.
Alternate Requirements
(Room/Area Specific
Up to 50% of re-lamping related wattage can be other than fluorescent.
Bathroom, Garage, Laundry, & Utility:
Manual-on occupancy sensor on lighting
All other rooms (Hallway, Dining, Bedroom, etc.)
Manual-on occupant sensor, or dimmer on all lighting.
Outdoor lighting attached to building:
Motion sensor plus photo control.
Building Permit Fees
Fees are charged for each type of permit issued such as building, plumbing, electrical and/or mechanical. The permit fee is based on the valuation and square footage of the project, and calculated from fee tables established in the code. The fees provide for the application process, review of plans, and adequate field inspection of the materials and methods of construction.
All permits issued require an inspection during and/or at completion of the work. Scheduling inspections is the responsibility of the permittee. Depending on the type of project, the following inspections are required:

Foundation - to be made after the trenches are excavated, forms erected and steel & holdowns are in place. Property lines shall be marked at the site by the applicant, developer, contractor, authorized agent, or engineer prior to requesting an inspection and shall be clearly visible for the county inspector.

Underslab-Underfloor - to be made after the installation of underfloor framing, heating ducts and plumbing.

Underfloor Insulation - to be made after the floor insulation and underfloor ventilation and access is installed but prior to installation of the subfloor.

Roof Nail - to be made after installation and nailing of the roof sheathing and flashing.

Frame - to be made after the roof, all framing, fire blocking, lath and bracing are in place and all pipes, chimney vents, rough electrical mechanical and plumbing are installed.

Insulation/Caulking - to be made after all the caulking, wall and ceiling insulation is installed.

Drywall Nail - to be made after the drywall is installed and prior to tape or texture.

Final - to be made after finish grading and the building is completed and ready for occupancy.

Not all of the inspections listed above will apply to every job. If it is uncertain which inspections will pertain to your project, check with the Building Division. Rule of thumb: "Don't cover it until the inspector sees it."
Environmental Health
The issuance of the building permit will be contingent upon approval by Environmental Health. The addition must not encroach upon the existing septic system or area reserved for expansion thereof.

In those cases where expansion of the septic system is deemed necessary, a permit to do so is required.
When To Call For an Inspection
For your convenience, the Building Division provides a 24-hour inspection requests line. When you call please leave the permit number, address and type of inspection requested. Inspections will be made on the day following request. The approved plans and the inspection card should be on the job site and available to the inspector at the time of inspection. Building Inspection Requests (707) 784-4750.
Important Numbers
Department of Resource Management
The Building, Planning, Public Works, and Environmental Health Divisions are located at 675 Texas Street, Suite 5500, Fairfield. (707) 784-6765