Buildings Bulletin 2016-12 was released in order to clarify how surface areas will be calculated in order to determine if a proposed extension, renovation, elevation and such will be considered as a New Building and will therefore be required to comply with the latest version of the Construction Code. Here is a quick explanation.
The 2014 New York City Administrative Code (AC) Section 28-101.4.5 states, in part, the following:
§28-101.4.5 Work that increases existing floor surface area of a prior code building by more than 110 percent. Notwithstanding sections 28-101.4.3 and 28-102.4.3 or any other provision of this code that would authorize alterations of prior code buildings in accordance with the 1968 Building Code or prior Codes, where the proposed work at the completion of construction will increase the amount of floor surface area of a prior code building by more than 110%, over the amount of existing floor surface area, such entire building shall be made to comply with the provisions of this code as if it were a new building hereafter erected.
Exceptions: When determining the amount of existing floor surface area for the purposes of section 28-101.4.5, the following shall be excluded from the measured square footage of floor surface area:
1. The square footage of floors removed during the course of the work when such floors are removed together with the supporting beams, joists, decking and slabs on grade. Floor surface area is defined in section AC 28-101.4.5.2 as follows:
FLOOR SURFACE AREA. Floor surface area is the gross square foot area of all horizontal floor and roof surfaces, including roofs of bulkheads and superstructures, of a building or structure at any level, including cellar, attic and roof.
What It Means?
If any horizontal surface including floors and roofs are removed entirely together with other existing structures of the building, it shall not be excluded in the calculation as part of the existing floor surface area, however if the floor, roof or other horizontal structure is removed together with the existing structures and later on replaced then it shall be included as part of the proposed floor surface area.
All pitched roof including those with multiple dormers, gables and/or chimneys will be calculated based on their horizontal footprint – as if viewed directly above – for the purpose of calculating the floor surface area. The floor surface area of the roof however, is limited to its horizontal footprint that is bounded by the exterior walls of the building. Although an exception to this rule would be roofs covering porches and/or balconies which will be included in the surface area calculations even if they are not bounded by exterior walls.
It should be noted that attics are included or counted as floor surface areas. According to BC 202.1 an attic is the area between the ceiling beams on the top floor of the house and the rafters of the roof. If the attic has fixed stairs and/or headroom that is larger than or equal to 5 feet, then it is included in the surface area calculations. Now if there is any location in the attic that has a headroom greater or equal to 5 feet measuring from the roof rafters to the top of the ceiling beams or on the top of the floor but no floor is laid, the entire attic’s floor area will be included in the floor surface area calculations.
If there will be strengthening works for structural support including sistering floor joists or such modifications to the floor and/or roof assembly and the existing structure will remain and continue to carry load, everything will be included in the existing floor surface area.
An enclosed space that has five feet or larger headroom underneath a building will also be included in the floor surface area calculation regardless if a floor has been laid or not.
Floor surface area calculation will also include balconies and covered porches, however, uncovered decks and porches shall not be included in the calculations.
Calculations for Increase in Floor Surface Area
Floor surface area calculations will follow a particular formula and to define the percentage by which the floor area will increase, you will need 2 things, existing-to-remain as well as the proposed measurements.
Operational Requirements
If the floor area will be increase by more than 110% then the application is to be identified as “Alteration Type 1 required to meet New Building requirements (28-101.4.5)”, you will find this in sections 5 and 9 of the PW1. You have to remember that New Building cannot be designated if any part of the existing building is to remain, whether it’s part of the old foundation, façade or any old structure that will be integrated into the new construction. It will only be filed as an “alteration type 1 required to meet New Building requirement (28-101.4.5).”
Should a change in the scope of works occur during construction that will result in the increase of total floor surface area that will be greater than 110% as per AC 28-101.4.5.1, then the application filed must be amended to pinpoint the scope of work added. All documentation and forms that will be affected by the change needs to be refiled in order to address the ongoing construction as “Alteration required to meet New Building requirements.” In such cases, all construction activities except necessary emergency works will be halted until the post-approval amendment is approved.