Section BO105 — ALTERATIONS

Alterations to existing buildings shall comply with the provisions of this code for new construction, except as permitted by Sections BO105.2 through BO105.8. Engineered design in accordance with Section R301.1.3 shall be permitted to meet the requirements of this section. Alterations shall not cause the existing building to become less compliant with the provisions of this code for new construction than the existing building was prior to the work.

Newly constructed elements, components and systems shall comply with the requirements of this code.

Exceptions:

1. Added openable windows are not required to comply with the light and ventilation requirements of Section R325.
2. Newly installed electrical equipment shall comply with the requirements of Section BO105.5.

The work shall not increase the extent of noncompliance or create nonconformity to those requirements that did not previously exist.

Altered structural elements and systems shall comply with Section R102.6.1 and the structural provisions of this appendix.

BO105.4.1 Decreased structural capacity. Where an alteration causes a decrease in capacity in any structural component, that structural component shall be shown to comply or shall be altered to comply with the applicable provisions of Chapters 3, 4, 5, 6 and 8.

BO105.4.2 Increased design loads. Where an alteration causes an increase in loads as described in this section, the existing structural components that support the increased load, including the foundation, shall be shown to comply or shall be altered to comply with the applicable provisions of Chapters 3, 4, 5, 6 and 8. Existing structural components that do not provide support for the increased loads shall not be required to comply with this section.

BO105.4.2.1 Dead load increase. Dead load shall be considered to be increased for purposes of this section when the weight of materials used for the alteration exceeds the weight of the materials replaced, or when new materials or elements are added.

Exceptions:

1. Buildings in which the increase in dead load is due entirely to the addition of a second layer of roof covering weighing 3 pounds per square foot (psf) (0.1437 kN/m [2] ) or less over an existing single layer of roof covering.
2. Installation of rooftop-mounted photovoltaic (PV) panel systems weighing 4 psf (0.1915 kN/m [2] ) or less over an existing single layer of roof covering.

These exceptions shall not be applied simultaneously.

BO105.4.2.2 Live load increase. An increase in live load shall be determined based on Table R301.5.

BO105.4.2.3 Snow load increase. Snow load shall be considered to be increased for purposes of this section when alteration of the roof configuration creates new areas that accumulate drifted snow.

BO105.4.2.4 Wind load increase. Wind load shall be considered to be increased for purposes of this section when the exposed surface area of any exterior elevation subject to wind pressure is increased by more than 5 percent.

APPENDIX BO-4 2025 CALIFORNIA RESIDENTIAL CODE

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APPENDIX BO — EXISTING BUILDINGS AND STRUCTURES

BO105.4.2.5 Seismic load increase. Seismic load shall be considered to be increased for purposes of this section in existing buildings assigned to Seismic Design Category C, D 0, D 1 or D 2 where new materials replace lighter-weight materials in one of the following conditions:

1. Concrete tile or tile roof covering of similar weight is installed on more than 50 percent of the total roof area.
2. Brick veneer or cladding of similar weight is installed on walls above the second story.

purposes of this section in existing buildings assigned to Seismic Design Category C, D 0, D 1 or D 2 where new materials replace lighter-weight materials in one of the following conditions:

1. Concrete tile or tile roof covering of similar weight is installed on more than 50 percent of the total roof area.
2. Brick veneer or cladding of similar weight is installed on walls above the second story.

BO105.4.3 Unreinforced masonry parapets. Unreinforced masonry parapets located in Seismic Design Category D2 shall have wall anchors installed at the roofline and additional bracing installed above the roofline whenever a reroofing permit is issued and work involves removal of roofing materials from more than 25 percent of the roof area. Such masonry bracing and wall anchors shall be of an approved design, unless an evaluation demonstrates compliance of the existing bracing and anchorage.

Exception: Bracing above the roofline shall not be required where the maximum height of unbraced unreinforced masonry does not exceed a height-to-width ratio of 2.5. Height shall be measured from the top of the parapet down to the highest existing brace or anchor point attached to the structure.

Electrical equipment and wiring shall comply with this section.

BO105.5.1 Materials and methods. Newly installed electrical equipment and wiring relating to work done in any work area, including in newly installed partitions and ceilings, shall comply with the materials and methods requirements of Chapters 34 through 43.

BO105.5.2 Electrical service. Service to the dwelling unit shall be not less than 100 ampere, three-wire capacity, and service equipment shall be dead front having no live parts exposed that could allow accidental contact. Type “S” fuses shall be installed where fused equipment is used.

Exception: Existing service of 60 ampere, three-wire capacity, and feeders of 30 ampere or larger two- or three-wire capacity shall be accepted if adequate for the electrical load being served.

BO105.5.3 Additional electrical requirements. Where the work area includes any of the following areas within a dwelling unit, the requirements of Sections BO105.5.3.1 through BO105.5.3.5 shall apply.

BO105.5.3.1 Enclosed areas. Enclosed areas other than closets, kitchens, basements, garages, hallways, laundry areas and bathrooms shall have not fewer than two duplex receptacle outlets, or one duplex receptacle outlet and one ceiling- or walltype lighting outlet.

BO105.5.3.2 Kitchen and laundry areas. Kitchen areas shall have not fewer than two duplex receptacle outlets. Laundry areas shall have not fewer than one duplex receptacle outlet located near the laundry equipment and installed on an independent branch circuit.

BO105.5.3.3 Ground-fault circuit interruption. Ground-fault circuit interruption shall be provided on newly installed receptacle outlets if required by Chapters 34 through 43.

BO105.5.3.4 Lighting outlets. Not less than one lighting outlet controlled by a listed wall-mounted device shall be provided in every bathroom, hallway, stairway, attached garage and detached garage with electric power to illuminate outdoor entrances and exits, and in utility rooms and basements where these spaces are used for storage or contain equipment requiring service. The wall-mounted control device shall be located near an entrance to the room.

BO105.5.3.5 Clearance. Clearance for electrical service equipment shall be provided in accordance with Chapters 34 through 43.

Reconfigured spaces intended for occupancy and spaces converted to habitable or occupiable space in any work area shall be provided with ventilation in accordance with Section R325.

Where a habitable attic or habitable space is created in an existing building, ceiling heights shall be not less than 6 feet 8 inches (2032 mm). Bathrooms, toilet rooms and laundry rooms shall have a ceiling height of not less than 6 feet 4 inches (1930 mm).

Exceptions:

1. For rooms with sloped ceilings, the required floor area of the room shall have a ceiling height of not less than 5 feet (1524 mm), and not less than 50 percent of the required floor area shall have a ceiling height of not less than 6 feet 8 inches (2134 mm).
2. At beams, girders, ducts or other obstructions, the ceiling height shall be not less than 6 feet 4 inches (1930 mm) from the finished floor.

Stairs, handrails and guards shall comply with this section.

BO105.8.1 Stair width. Existing basement stairs and handrails not otherwise being altered or modified shall be permitted to maintain their current clear width at, above and below existing handrails.

BO105.8.2 Stair headroom. Headroom height on existing basement stairs being altered or modified shall not be reduced below the existing stairway finished headroom. Existing basement stairs not otherwise being altered shall be permitted to maintain the current finished headroom.

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APPENDIX BO — EXISTING BUILDINGS AND STRUCTURES

BO105.8.3 Stair landing. Landings serving existing basement stairs being altered or modified shall not be reduced below the existing stairway landing depth and width. Existing basement stairs not otherwise being altered shall be permitted to maintain the current landing depth and width.

BO105.8.4 Stair treads and risers. An existing stairway shall not be required to comply with Section R318.7.5 where the existing space and construction does not allow a reduction in pitch or slope. Where risers are added to an existing stair, the tread and riser dimension of the added risers shall match the existing stair.

BO105.8.5 Stairway illumination. Stairways within the work area shall be provided with illumination in accordance with Section R325.7.

BO105.8.6 Handrails and guards. If a stair or any portion of a stair is altered, a handrail and guard, where required, shall be provided in accordance with Sections R318 and R320.