Multiple dwelling buildings include all forms of residential buildings, high-rise or low-rise, occupied for permanent residence and any alteration project involving the enlargement or conversion of an existing building with 3 or more dwelling units in the following types of buildings:
Residential Multi-family Building (Class A Multiple Dwellings), which are included in occupancy classification R-2, per BC 310.1.2
Mixed Use building that includes residential units
Existing non-residential to residential conversion. For example, a conversion of a warehouse or portion thereof, to a residential building, which may be considered a Loft Conversion.
Alteration work always results in the issuance of a new or amended Certificate of Occupancy (CO), and may include enlargements and/or conversions. In addition to horizontal and vertical enlargements of a building, an alteration project may also include a change to the building’s egress, zoning use group, and/or Building Code occupancy classification. Types of alteration work may include any combination of the following:
Vertical and Horizontal Enlargements. An addition to the floor area in an existing building.
Conversions. A change of an existing use or a new use, in an area not previously used for such purpose. A conversion is a change of “use” as defined by the Zoning Resolution (ZR), and/or a change in the “occupancy classification” as defined in BC Chapter 3. A use or occupancy classification of a building is any purpose for which it is designed, arranged, maintained or occupied.
Egress Modifications. Any substantive change in the exiting width, length of travel distance, exit locations, or occupancy load of the building impacting the exits, or any change in number of required exits in a building.
Floor Area Reductions. A reduction to an existing building’s floor area that impacts the Certificate of Occupancy. For example, the complete elimination of one or more stories from a building, the demolition of a public assembly space on the top floor, etc.
Residential alterations may also include incidental uses, which are ancillary functions associated with a given occupancy, such as mechanical rooms, and/or boiler rooms of a certain size that carry different level of risk to that occupancy.
A new building is classified as a low-rise or high-rise depending on the building’s height from the lowest level of fire department vehicle access. Buildings below 75 feet are defined as low rise, while building above 75 are defined as high-rise.
High rise buildings are subject to special regulations in the Building Code for construction classification, elevators, egress and fire protection, and special regulations in the Zoning Resolution related to Quality Housing, Inclusionary Housing, and additional bulk regulations related to the zoning district.
There are several accessory uses associated with a new low or high-rise residential building that may include parking, storage, and other residential amenities such as fitness areas, pools, etc. The parts of this guideline that apply only to high rise construction have been highlighted in light gray and would not apply to low-rise construction.
When proposed alteration work in a prior code building increases the existing floor surface area, as defined in AC 28-101.4.5, by more than 110 percent, such building must be designed in accordance with the 2014 Construction Codes as if it were a new building. However, per AC 28-22.214.171.124, the Zoning Resolution may still be applied to any nonconforming use or non-complying bulk of the building.
Minor enlargements that do not add or eliminate any rooms or change the number of floors as indicated on the existing CO are considered renovation projects. For alterations of residential portions of mixed use buildings, see Commercial Mixed Use Alterations Project Guidelines.
Building Systems, such as new or modified plumbing, HVAC, or gas systems could be involved in an Alteration Project and are better described under the various Building System Guidelines.
An alteration project shall not be filed as a renovation project.
Curb Cuts, Builder’s Pavement Plans, Public Right-of-Way Encroachments, and Antennas may be part of an alteration project’s scope of work; see guidelines for these various alteration and renovation projects for more information.
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