An addition to a building or structure shall comply with the International Codes as adopted for new construction without requiring the existing building or structure to comply with any requirements of those codes or of these provisions, except as required by this chapter. Where an addition impacts the existing building or structure, that portion shall comply with this code.
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An addition shall not create or extend any nonconformity in the existing building to which the addition is being made with regard to accessibility, structural strength, fire safety, means of egress, or the capacity of mechanical, plumbing, or electrical systems.
Any repair or alteration work within an existing building to which an addition is being made shall comply with the applicable requirements for the work as classified in Chapter 5.
No addition shall increase the height of an existing building beyond that permitted under the applicable provisions of Chapter 5 of the International Building Code for new buildings.
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No addition shall increase the area of an existing building beyond that permitted under the applicable provisions of Chapter 5 of the International Building Code for new buildings unless fire separation as required by the International Building Code is provided.
Exception: In-filling of floor openings and nonoccupiable appendages such as elevator and exit stair shafts shall be permitted beyond that permitted by the International Building Code.
Existing fire areas increased by the addition shall comply with Chapter 9 of the International Building Code.
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Additions to existing buildings or structures are new construction and shall comply with the International Building Code.
Existing structural elements supporting any additional gravity loads as a result of additions shall comply with the International Building Code.
Exceptions:
- Structural elements whose stress is not increased by more than 5 percent.
- Buildings of Group R occupancy with no more than five dwelling units or sleeping units used solely for residential purposes where the existing building and the addition comply with the conventional light- frame construction methods of the International Building Code or the provisions of the International Residential Code.
The lateral force-resisting system of existing buildings to which additions are made shall comply with Sections 1103.3.1, 1103.3.2 and 1103.3.3.
Exceptions:
- Buildings of Group R occupancy with no more than five dwelling or sleeping units used solely for residential purposes where the existing building and the addition comply with the conventional light-frame construction methods of the International Building Code or the provisions of the International Residential Code.
- In other existing buildings where the lateral-force story shear in any story is not increased by more than 10 percent cumulative.
Any element of the lateral force-resisting system of an existing building subjected to an increase in vertical or lateral loads from the vertical addition shall comply with the International Building Code wind provisions and the IBC-level seismic forces specified in Section 301.1.4.1 of this code.
Where horizontal additions are structurally connected to an existing structure, all lateral force-resisting elements of the existing structure affected by such addition shall comply with the International Building Code wind provisions and the IBC-level seismic forces specified in Section 301.1.4.1 of this code.
[B] 1103.3.3 Voluntary Addition of Structural Elements to Improve the Lateral Force-Resisting System
Voluntary addition of structural elements to improve the lateral force-resisting system of an existing building shall comply with Section 807.6.
Any structural element of an existing building subjected to additional loads from the effects of snow drift as a result of an addition shall comply with the International Building Code.
Exceptions:
- Structural elements whose stress is not increased by more than 5 percent.
- Buildings of Group R occupancy with no more than five dwelling units or sleeping units used solely for residential purposes where the existing building and the addition comply with the conventional light-frame construction methods of the International Building Code or the provisions of the International Residential Code.
Additions and foundations in flood hazard areas shall comply with the following requirements:
- For horizontal additions that are structurally interconnected to the existing building:
- If the addition and all other proposed work, when combined, constitute substantial improvement, the existing building and the addition shall comply with Section 1612 of the International Building Code.
- If the addition constitutes substantial improvement, the existing building and the addition shall comply with Section 1612 of the International Building Code.
- For horizontal additions that are not structurally interconnected to the existing building:
- The addition shall comply with Section 1612 of the International Building Code.
- If the addition and all other proposed work, when combined, constitute substantial improvement, the existing building and the addition shall comply with Section 1612 of the International Building Code.
- For vertical additions and all other proposed work that, when combined, constitute substantial improvement, the existing building shall comply with Section 1612 of the International Building Code.
- For a new, replacement, raised, or extended foundation, if the foundation work and all other proposed work, when combined, constitute substantial improvement, the existing building shall comply with Section 1612 of the International Building Code.
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Where an addition is made to a building or structure of a Group R or I-1 occupancy, the existing building shall be provided with smoke alarms as required by Section 1103.8 of the International Fire Code or Section R314 of the International Residential Code as applicable.
Additions to existing buildings shall conform to the energy requirements of the International Energy Conservation Code or International Residential Code as they relate to new construction.