Arpit Jain 12 min February 23, 2026

Navigating Wind & Seismic Design Loads in New York State: A Code-Based Guide

Direct Answer: Wind & Seismic Load Requirements in NYS

For all projects governed by the 2020 Building Code of New York State (BCNYS), structural design for wind and seismic loads must comply with the requirements of the American Society of Civil Engineers' ASCE/SEI 7-16, Minimum Design Loads and Associated Criteria for Buildings and Other Structures. This standard is explicitly referenced by the BCNYS for all lateral load calculations.

Here are the key takeaways for determining wind and seismic loads in New York State (outside of NYC):

• Governing Code: The 2020 Building Code of New York State (BCNYS), which is based on the 2018 International Building Code (IBC) with NYS-specific amendments.
• Referenced Standard for Loads: ASCE 7-16 is the primary source for all methodologies, maps, and tables related to wind, seismic, snow, and other structural loads.
• Wind Loads (e.g., Long Island): The 'ultimate design wind speed' (Vult) is determined from maps in ASCE 7-16 Chapter 26 (Figures 26.5-1A through 26.5-1D). The correct map depends on the building's Risk Category, as defined in BCNYS Table 1604.5. For a standard office building (Risk Category II) on Long Island, Vult is approximately 120-130 mph.
• Seismic Loads (e.g., Westchester County): The Seismic Design Category (SDC) is determined through a multi-step process outlined in ASCE 7-16 Chapter 11. This involves finding mapped spectral acceleration parameters (Ss and S1), identifying the soil Site Class (often from a geotechnical report), and using the building's Risk Category to find the final SDC from ASCE 7-16 Tables 11.6-1 and 11.6-2.

Load Type	Governing Code Section (2020 BCNYS)	Referenced Standard & Chapter	Key Input Parameters
Wind Loads	§1609	ASCE 7-16, Chapters 26-31	Ultimate Design Wind Speed (Vult), Risk Category, Exposure Category, Topography
Seismic Loads	§1613	ASCE 7-16, Chapters 11-23	Mapped Accelerations (Ss, S1), Risk Category, Site Class, Seismic Importance Factor (Ie)

Important Note: This guidance applies to jurisdictions that have adopted the New York State Uniform Fire Prevention and Building Code. The City of New York has its own distinct set of Construction Codes, including the 2022 NYC Building Code, which must be used for all projects within the five boroughs.

Why Accurate Lateral Load Calculations Matter

In structural engineering, accurately calculating and designing for lateral loads—primarily wind and seismic forces—is fundamental to life safety and building resilience. These forces act horizontally on a structure, and if not properly accounted for, can lead to catastrophic failure. For architects, engineers, and plan reviewers in New York State, mastering these requirements is not just about compliance; it's about safeguarding occupants and investments.

This topic typically emerges during the Schematic Design and Design Development phases of a project, where the structural system is being defined. The initial determination of wind speeds and the Seismic Design Category dictates:

• The required strength and stiffness of the lateral force-resisting system (e.g., moment frames, braced frames, shear walls).
• Foundation design requirements.
• Anchorage and bracing requirements for nonstructural components like MEP equipment, cladding, and ceilings.
• Special inspection and structural observation requirements during construction.

A common pitfall is using outdated standards (e.g., ASCE 7-10 or 7-05) or misinterpreting the specific maps and tables within ASCE 7-16. Another significant point of confusion is the jurisdictional divide between the BCNYS and the NYC Building Code, which are not interchangeable.

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When calculating wind loads for a building on Long Island, which ASCE 7 version is referenced by the 2020 BCNYS, and how do I find the correct 'ultimate design wind speed' for that specific location?

The 2020 Building Code of New York State (BCNYS) explicitly references the 2016 edition of ASCE/SEI 7 for determining wind loads. The correct 'ultimate design wind speed' (Vult) for a project on Long Island (Nassau or Suffolk County) is found on the wind speed maps in ASCE 7-16, Chapter 26, based on the building's designated Risk Category.

Here is the detailed process:

1. Confirm the Referenced Standard: BCNYS §1609.1.1 ("Determination of wind loads") states that "Wind loads on every building or structure shall be determined in accordance with Chapters 26 to 31 of ASCE 7…" The code further clarifies in Chapter 35 that the referenced edition is ASCE 7-16.

2. Determine the Building's Risk Category: Before you can find the wind speed, you must classify the building's use and occupancy to determine its Risk Category. This is done using BCNYS Table 1604.5, "Risk Category of Buildings and Other Structures."

   • Risk Category I: Low hazard to human life (e.g., agricultural facilities).
   • Risk Category II: Most common buildings not assigned to other categories (e.g., offices, retail, residential).
   • Risk Category III: Buildings with a substantial number of occupants or that pose a substantial hazard if they fail (e.g., schools, theaters, healthcare facilities with fewer than 50 residents).
   • Risk Category IV: Essential facilities (e.g., hospitals, fire stations, emergency shelters).

3. Find the Ultimate Design Wind Speed (Vult): With the Risk Category established, refer to the wind speed maps in ASCE 7-16, Chapter 26.

   • Figure 26.5-1A: For Risk Category II buildings.
   • Figure 26.5-1B: For Risk Category III buildings.
   • Figure 26.5-1C: For Risk Category IV buildings.
   • (Figure 26.5-1D is for Risk Category I).

   For a project located on Long Island, the approximate Vult values from these maps are:

   • Risk Category II: 120-130 mph
   • Risk Category III: 130-140 mph
   • Risk Category IV: 140-150 mph

   These are ultimate wind speeds, which correspond to different mean recurrence intervals depending on the Risk Category. They are used directly in the ASCE 7-16 wind load equations and should not be confused with the nominal wind speeds used in older versions of the standard (like ASCE 7-05). For precise values, you can use the online ATC Hazards by Location tool, which is a recognized resource for interpolating these maps based on a specific site latitude and longitude.

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How do I find out the seismic design category for my project in Westchester County, NY?

To determine the Seismic Design Category (SDC) for a project in Westchester County, you must follow the detailed procedure in ASCE 7-16, Chapter 11, as mandated by BCNYS §1613. The process involves combining site-specific ground motion data with the building's soil type and risk category to classify the level of required seismic detailing.

Here is the step-by-step method:

Step 1: Determine Mapped Spectral Response Acceleration Parameters (Ss and S1)

These values represent the maximum considered earthquake ground motion for short periods (Ss) and 1-second periods (S1).

• Source: You can find these values from the maps in BCNYS Figures 1613.2(1) through 1613.2(12).
• Best Practice: The most accurate method, explicitly permitted by ASCE 7-16 §11.4.1, is to use a web-based tool like the U.S. Geological Survey (USGS) Seismic Design Web Services or the ATC Hazards by Location tool. By entering the project's address or coordinates, you get precise Ss and S1 values. For a typical location in White Plains, Westchester County, Ss is approximately 0.25g and S1 is approximately 0.07g.

Step 2: Determine the Site Class

The Site Class characterizes the soil profile at the project location and significantly affects how seismic waves are amplified.

• Source: Site Class is defined in ASCE 7-16 Chapter 20 and BCNYS Table 1613.2.5(1). The classifications range from A (hard rock) to F (soft soils requiring site-specific evaluation).
• Requirement: The best way to determine Site Class is with a geotechnical report.
• Default: If a geotechnical investigation has not been performed, BCNYS §1613.2.5.2 requires you to assume Site Class D, unless the building official or geologic data determines that Site Class E or F soils are likely present.

Step 3: Calculate Site-Modified and Design Spectral Response Parameters

The mapped values (Ss and S1) are adjusted for the soil type to get the design values (SDS and SD1).

1. Find Site Coefficients (Fa and Fv): Using the determined Site Class and the mapped Ss and S1 values, find the coefficients Fa and Fv from ASCE 7-16 Tables 11.4-1 and 11.4-2, respectively.
2. Calculate Site-Modified Values (SMS and SM1):
   • S_MS = Fa * Ss
   • S_M1 = Fv * S1
3. Calculate Design Values (SDS and SD1):
   • SDS = (2/3) * SMS
   • SD1 = (2/3) * SM1

Step 4: Determine the Seismic Design Category (SDC)

Finally, the SDC is determined using the building's Risk Category (from BCNYS Table 1604.5) and the calculated design parameters.

1. Using the Risk Category and the value of S_DS, find the SDC from ASCE 7-16 Table 11.6-1.
2. Using the Risk Category and the value of S_D1, find the SDC from ASCE 7-16 Table 11.6-2.

The more severe SDC from the two tables governs the project's design. For most buildings in Westchester County on a default Site Class D soil, the SDC will typically be SDC B or SDC C.

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Additional Considerations for NYS Structural Design

Jurisdictional Variations: New York State vs. New York City

It is absolutely critical for design professionals to understand that the New York State Uniform Code and the New York City Construction Codes are entirely separate legal and technical documents.

• New York State (BCNYS): Applies to all 62 counties except for the five boroughs of New York City. It is based on the International Codes (I-Codes) with state-specific amendments.
• New York City (NYCBC): Applies only within Manhattan, the Bronx, Brooklyn, Queens, and Staten Island. The 2022 NYC Building Code is a unique document with its own structure, amendments, and local laws. While it also references ASCE 7-16, it has its own specific wind speed maps (Figure 1609.3(1)) and seismic provisions that differ from the BCNYS.

Never use the BCNYS for a project in NYC, or vice versa. Doing so will result in an immediate rejection during plan review.

The Role of Geotechnical Reports in Seismic Design

While the BCNYS allows for a default Site Class D in the absence of a soils report, relying on this default can have significant consequences. A geotechnical investigation provides the actual soil properties at the site, which may reveal a better Site Class (e.g., C), potentially reducing the seismic design forces and leading to a more economical structure. Conversely, it could reveal poorer soils (e.g., E or F) that require more robust and costly seismic detailing, which is critical for safety. For any significant project, a geotechnical report is an essential investment for both safety and cost-effectiveness.

Coordination Between Structural and Other Disciplines

The determined wind and seismic loads have ripple effects across the entire design team:

• Architects: Wind pressures directly inform the required Design Pressure (DP) ratings for windows, curtain walls, and doors. Wind uplift forces dictate roof assembly specifications. Seismic Design Category influences requirements for cladding anchorage and interior partition detailing.
• MEP Engineers: The SDC dictates the level of seismic bracing and anchorage required for ductwork, piping, conduits, and equipment (e.g., boilers, chillers, generators). These requirements are detailed in ASCE 7-16 Chapter 13, "Seismic Design of Nonstructural Components." Failure to coordinate these requirements early can lead to costly retrofits and inspection failures.
• Code Officials and Inspectors: Plan reviewers will verify that the correct ASCE 7 version, Risk Category, and site parameters were used. During construction, special inspectors will be required to verify the installation of the lateral force-resisting system (e.g., welding, high-strength bolting, concrete reinforcement) and the anchorage of nonstructural components in higher SDCs.

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Frequently Asked Questions (FAQ)

1. What version of the building code is currently in effect in New York State (outside NYC)? The 2020 New York State Uniform Fire Prevention and Building Code is the currently effective code suite, which includes the 2020 Building Code of New York State (BCNYS).

2. Does the BCNYS apply in New York City? No. New York City enforces its own separate codes, most notably the 2022 NYC Building Code. The BCNYS does not apply within the five boroughs.

3. What is ASCE 7 and why is it important? ASCE 7, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, is a nationally recognized standard that provides the technical methodology for calculating structural loads (wind, seismic, snow, rain, ice, etc.). The BCNYS and other building codes adopt it by reference, making its provisions legally enforceable.

4. Can I use an online tool to find my wind and seismic values? Yes. ASCE 7-16 specifically permits the use of online resources like the ATC Hazards by Location tool and the USGS Seismic Design Web Services. These tools provide more precise, site-specific values than reading from the printed maps in the code.

5. What is a "Risk Category" and how do I find it? A Risk Category classifies a building based on its use and the potential risk to human life in the event of a failure. It is a critical input for determining wind, seismic, and snow loads. You can find the classification for your building in 2020 BCNYS Table 1604.5.

6. Do I need a special inspection for seismic or wind resistance? Yes, often. BCNYS Chapter 17 outlines special inspection requirements. For wind, this may include inspections for high-load diaphragms and roof systems. For seismic, designated seismic systems in SDC C and higher require extensive special inspection of structural steel, concrete, and other components.

7. How do snow loads in NYS compare to wind and seismic loads? In many parts of Upstate New York, snow loads (governed by BCNYS §1608) can be the dominant vertical design load. However, wind and seismic are the primary lateral (horizontal) loads that govern the design of the lateral force-resisting system. All applicable load combinations must be checked.

8. Are there different wind load requirements for coastal areas like Long Island? Yes. The wind speed maps in ASCE 7-16 show significantly higher wind speeds along coastal areas like Long Island, the Hudson Valley, and areas near the Great Lakes. These areas also have a higher likelihood of being classified as Exposure Category C or D, further increasing the design wind pressures.

9. Does the Residential Code of NYS have the same structural load requirements? The 2020 Residential Code of New York State (RCNYS) contains its own prescriptive provisions for conventional light-frame construction in Chapter 3. However, for homes that fall outside these prescriptive limits or are located in high-wind or high-seismic areas, the design must be done in accordance with the BCNYS and ASCE 7-16.

10. What happens if I don't have a geotechnical report for my project? For seismic design, the BCNYS requires you to assume a conservative default of Site Class D. This could result in an over-designed and more expensive structural system if the actual soil conditions are better. For foundation design, the lack of a report means you must use presumptive load-bearing values from BCNYS Table 1806.2, which may not be accurate for the site.