{"data":{"id":"us-nyc/n.y.c.-admin.-code-ebc-703","jurisdiction":"us-nyc","citation":"N.Y.C. Admin. Code § EBC 703","heading":"Section EBC 703: General Design Requirements","body":"703.1 General.\n\nAll structural alterations shall comply with this section and Sections 704 through 710, as applicable. All new structural elements and their connections shall comply with the New York City Building Code.\n\n703.1.1 Underpinning and alternative methods of support of buildings and adjacent property.\n\nUnderpinning and alternative methods of support of buildings and adjacent property shall comply with the requirements of Chapters 18 and 33 of the New York City Building Code.\n\n703.1.2 Separated buildings and structures.\n\nWhere the structural alteration is completely separated from an existing building or structure by a joint, only this isolated part shall be made to comply with the New York City Building Code as a new building. Unless determined by calculations, the joint shall be twice of that indicated in Section 1613.4 of the New York City Building Code.\n\n703.1.3 Repairs due to accidental events.\n\nUnless otherwise specified in this code, where damage to structural elements was the result of fire, vehicular impact, extreme environmental events or adjoining construction, structural repairs are permitted to only restore the structure to the condition prior to the event provided a registered design professional submits a report that such damage has not affected more than 20 percent of the structure.\n\n703.2 Buildings required to comply as hereafter erected.\n\nFor buildings subject to structural alterations that increase existing floor surface area of an existing building by more than 110 percent as described in Section 302.7 of this code, the structure of such entire building shall be made to comply with the structural provisions of the New York City Building Code as if it were a new building hereafter erected.\n\n703.3 Entire buildings required to comply with loading provisions.\n\nFor buildings subject to structural alterations that meet any of the criteria listed below, the structure of such entire building shall be made to comply with the structural loading provisions of the Section 705:\n\n1. Structural alterations in which gravity load-carrying structural elements are affected by work that involves a change to the gravity load path that supports more than 55 percent of the total floor and roof area of the building or structure. The areas to be counted toward the 55 percent shall include mezzanines, penthouses, and in-filled courts and shafts tributary to the altered structural elements.\n\n2. Where a building or portion greater than 10 percent thereof, or greater than 20,000 square feet, is subject to a change of occupancy that results in the building being assigned to a higher Risk Category, based on Table 1604.5 of the New York City Building Code. For buildings with an S\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\tDS\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t less than 0.33, increased seismic loads due solely to an increase in Risk Category, where the change in Risk Category is to Risk Category II or III, need not be considered.\n\n3. Where the total dead and live load of the entire building increases by more than 50 percent, unless the applicant demonstrates that the increased load is less than the original design load for the existing building or that the building demonstrates the existing capacity to withstand the new loads.\n\n4. Where the wind base shear or overturning in either orthogonal direction increases by more than 50 percent, unless the applicant demonstrates that the increase in total wind load is less than the original design load for the existing building or that the building possesses the existing capacity to withstand the new loads.\n\n5. Where the seismic base shear or overturning in either orthogonal direction increases by more than 50 percent, unless the applicant demonstrates that the increase in total seismic load is less than the original design load for the existing building or that the building possesses the existing capacity to withstand the new loads.\n\n703.4 Increased demand on existing structural elements and foundations.\n\nAlterations not meeting the criteria in Sections 703.2 or 703.3 shall comply with Sections 703.4.1 and 703.4.2.\n\n703.4.1 Effects on structural elements.\n\nAny existing structural element for which a structural alteration causes an increase in demand, or causes a decrease in capacity, including stability, shall be made to comply with the structural loading provisions of Section 705. The effect of the additional loads or decreasing capacity shall be considered through the load path until resolved in the subgrade.\n\nExceptions:\n\n1. If the structural alteration does not increase the seismic mass of the building by more than 10 percent, nor decreases the lateral earthquake load resisting capacity of the building by more than 10 percent in either orthogonal direction, additional earthquake loads on the building’s lateral load resisting system due to the alteration need not be considered.\n\n2. \n\t\t\t\t\t\t\t\t\t\t\t\t\tIf the structural alteration does not increase the wind sail area of the building in each orthogonal direction by more than 10 percent, nor decrease the lateral wind load resisting capacity of the building by more than 10 percent in any direction, the additional wind loads need not be considered beyond the point that they have been delivered to the building structure’s main wind force resisting system.\n\n3. \n\t\t\t\t\t\t\t\t\t\t\t\t\tWhere a change in occupancy of less than 10 percent of a building area, or less than 20,000 square feet (1858 m\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t2\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t), requires a building to design for an increased snow, wind or seismic load due solely to being assigned a higher Risk Category, other than Risk Category IV, based on Table 1604.5 of the New York City Building Code, such change to the loads need not be considered.\n\n4. \n\t\t\t\t\t\t\t\t\t\t\t\t\tIncreased seismic loads due solely to an increase in Risk Category, where the change in Risk Category is to Risk Category II or III need not be considered. This exception shall not apply to buildings with an S\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\tDS\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t greater than 0.33.\n\n5. \n\t\t\t\t\t\t\t\t\t\t\t\t\tAn increase in demand on an element due to an increased dead load effect within the element due solely from the addition of a second layer of roof covering weighing 3 pounds per square foot (0.1437 kN/ m\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t2\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t) or less over an existing single layer of roof covering need not be cause to alter the element.\n\n703.4.2 Effects on foundations.\n\nEffects on foundations shall comply with Sections 703.4.2.1 and 703.4.2.2 of this code. Bearing values shall be as required by Chapter 18 of the New York City Building Code.\n\n703.4.2.1 New foundation elements.\n\nNew foundation elements shall comply with Chapter 18 of the New York City Building Code.\n\n703.4.2.2 Existing foundation elements.\n\nAny existing foundation element subjected to an increased load shall be made to comply with Chapter 18 of the New York City Building Code with the following exceptions.\n\nExceptions:\n\n1. Where the existing foundation design capacity is not known, structural alterations which increase the gravity load by 5 percent or less need not be made to comply. Where the gravity load is increased between 5 and 10 percent the registered design professional of record shall consider the impact of potential additional building movement.\n\n2. Structural alterations which increase the wind or seismic load by less than 20 percent need not be made to comply.\n\nExceptions 1 or 2 shall not be applicable a) where settlement or foundation movement is observed or has been documented, or b) where the proposed work reduces the bearing capacity of the soil strata providing support.\n\n703.5 Stability.\n\nStructural alterations shall comply with Sections 703.5.1, 703.5.2, and 703.5.3, as applicable.\n\n703.5.1 Stability index.\n\nWhere a structural alteration reduces the lateral stiffness of a building by more than 10 percent, the building’s lateral system or the altered elements of its lateral system shall have a stability index less than 0.25. Where the stability index is between 0.1 and 0.25, structural analysis and design shall include second order effects.\n\nThe stability index shall be determined as follows:\n\nUsing factored loads or service loads Q =\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\ta (S P) D\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tVh\n\nWhere:\n\nD = horizontal inter-story drift at a given story\n\nS P = total vertical gravity loads at and above a given story\n\nV = horizontal shear at a given story associated with D\n\nh = story height\n\na where using factored loads and a = 1.5 where using service loads\n\nException: Where a structural alteration is performed on an unreinforced masonry building with wood-framed floors constructed prior to 1903, apply Section 703.5.3.\n\n703.5.1.1 Reduction of stiffness.\n\nNo structural alteration shall reduce or modify the lateral stiffness of a building, or story within a building, unless it is demonstrated that the altered building structure, or story as applicable, has a stability index less than 0.10 or the altered building structure is made to comply with the structural provisions of the New York City Building Code.\n\n703.5.2 Buildings or stories initially out-of-plumb.\n\nWhere a structural alteration increases the lateral loads on a building or story, or reduces the lateral stiffness of a building or story, the analysis of the altered building or altered story shall include the effects of pre-existing horizontal out-of-plumbness in excess of 1 percent in the existing structural system. The initial out-of-plumbness shall be reported in accordance with Section 704 as appropriate and be evaluated to ensure the existing building is capable to sustain it prior to the alteration design. The pre-existing horizontal out-of-plumbness values shall be analyzed for their effect on the altered lateral system and their effects shall be additive to the drifts and forces due to wind and earthquake loading calculated in accordance with Section 705. Out of plumbness for each floor shall be measured from the floor elevations above and below to the most out-of-plumb location in the floor.\n\n703.5.3 Structural alterations of unreinforced masonry buildings with wood-framed floors constructed prior to 1903.\n\nStructural alterations of unreinforced masonry buildings with wood-framed floors constructed prior to 1903 shall comply with Sections 703.5.3.1 through 703.5.3.6:\n\n703.5.3.1 Reduction to in-plane stiffness.\n\nWhere a perimeter wall of a building is altered such that its in-plane stiffness is reduced by more than 30 percent, the building’s lateral system shall be made to resist a load of 20 psf in any direction. This notional 20 psf load shall be used in allowable load combinations in lieu of the earthquake and wind with a multiplier of 1 and should not be considered applied simultaneously on parallel walls.\n\n703.5.3.2 Walls.\n\nWhere the front or rear walls, or side walls fronting the public right of way, of a building are altered resulting in a final ratio of total horizontal length of opening area to total horizontal length of 50 percent or greater at any floor, the building’s lateral system shall be made to resist a load of 20 psf in any direction. This notional 20 psf load shall be used in allowable load combinations in lieu of the earthquake and wind with a multiplier of 1 and should not be considered applied simultaneously on parallel walls.\n\n703.5.3.3 Calculations.\n\nFor purposes of calculating reduction of lateral strength or stiffness of an existing building only, all existing bearing and non-bearing, interior or exterior, partitions shall be considered as part of the structure of the building. Where an interior wood stud or masonry or terra cotta cross wall of a building is removed, the building’s lateral system shall be reinforced with a structural system equivalent in stiffness and strength capacity to that of the removed wall calculated using the methods indicated in ASCE 41.\n\n703.5.3.4 Floor-to-floor heights.\n\nWhere the floor-to-floor heights of a building are increased as a result of an alteration such that the ratio of floor height to wall thickness exceeds 10, such walls shall be evaluated in accordance with TMS 402 including the effect of a 20 psf (LRFD) out-of-plane environmental load.\n\n703.5.3.5 Verification of connections.\n\nWhere any of the provisions of Sections 703.5.3.1 through 703.5.3.4 are triggered, it shall be verified that there are connections of the floor and roof framing to the posts and surrounding walls, including to the unreinforced masonry walls parallel to joists. Where no connections are present, connections shall be installed to provide a tensile capacity of 200 plf.\n\n703.5.3.6 Exposed walls.\n\nThe review of the structural stability of any exposed wall, including party walls after the neighboring structure has been removed, shall consider the engagement of perpendicular elements such as walls, floors and roofs. If the attachment of perpendicular elements is not anchored, connections shall be provided as required in Section 703.5.3.5.\n\n703.6 Exceptions from detailing requirements.\n\nExceptions from detailing requirements are permitted as allowed by Sections 703.6.1 and 703.6.2. Drawings shall include a statement as to non-compliant elements.\n\n703.6.1 Exception from continuity detailing requirements.\n\nNotwithstanding the requirements of Sections 703.2 and 703.3, existing structural elements need not comply with the continuity detailing requirements of the New York City Building Code unless required by Section 708 of this code.\n\n703.6.2 Exception from seismic detailing requirements.\n\nNotwithstanding the requirements of Sections 703.2 and 703.3, existing structural elements need not comply with the seismic detailing requirements of the New York City Building Code unless required by Section 708 of this code.\n\n703.7 Seismic separation requirements.\n\nFor altered buildings that must comply with Section 703.2 or 703.3 and are adjacent to or sharing unreinforced masonry walls, the structural requirements for seismic separation between the altered and existing structures shall be as follows:\n\n1. For alterations erected adjacent to lot line unshared unreinforced masonry bearing walls, the structural separation shall comply with Section 1613.4.1 of the New York City Building Code, except that existing lot line unshared masonry walls that are otherwise allowed to remain need not be demolished to provide for seismic separation.\n\n2. Where an existing building shares an unreinforced masonry party wall, there shall be no building separation between the altered and existing structure. The entire altered structure shall be designed to include an additional seismic load to account for the support of the party wall with connections capable of carrying a service (ASD) horizonal tension or compression load of 200 plf applied along each floor level, or a service (ASD) or 20 psf area load applied onto the party wall, whichever is larger. The connections shall be at the level of the floors of the adjoining building and shall not be set a distance larger than 8ft horizontally. Where floors do not exist, the distance between connections shall not exceed 15 ft vertically.\n\n3. No structural separation is required where:\n\n3.1. The neighboring structures are capable of transferring forces resulting from impact through diaphragms located at the same elevation.\n\n3.2. The structures are capable of resisting all required vertical and lateral forces considering the loss of any elements or components damaged by impact of the structures.\n\n3.3. An altered building, including its extension, is not required by this code to comply with seismic design.\n\n3.4. A party wall is shared by buildings less than 3 stories regardless of whether the design is governed by seismic demands.","path":["New York City Administrative Code","Title 28","Chapter 12: The New York City Existing Building Code (effective July 17, 2027)"],"source_url":"https://files.amlegal.com/pdffiles/NewYorkCity/Admin/XML.zip","current_through":"Local Law 2026/135 (enacted August 31, 2026)","vintage":"","retrieved_at":"2026-09-06T02:48:57Z","sha256":"82e113e24686e6a4d8dbead9d4cbdd7d1ca66f05297fbea13599225837340968","source_id":"us-nyc","stale":false,"prev":"us-nyc/n.y.c.-admin.-code-ebc-702","next":"us-nyc/n.y.c.-admin.-code-ebc-704"},"notice":"GroundRules: Original legal text. Not legal advice."}