Wind and seismic design parameters are the first structural items a plan reviewer checks. Before looking at member sizes, connection details, or foundation design, the reviewer needs to confirm that the design criteria shown on the structural drawings are correct for the project location, occupancy, and site conditions. Errors in ASCE 7 design parameters cascade through the entire structural design: a wrong Risk Category changes the wind speed map value, the seismic importance factor, and potentially the Seismic Design Category, which in turn changes the detailing requirements for every connection in the building.
This covers the most common ASCE 7 wind and seismic errors that generate plan review comments, based on ASCE 7-22 (with notes on differences from ASCE 7-16 where relevant).
Design criteria errors
Risk category classification
ASCE 7 Table 1.5-1 assigns Risk Categories (I through IV) based on the building's occupancy and use. Risk Category II covers most standard occupancies (offices, residential, retail). Risk Category III covers buildings with large occupant loads (assembly spaces over 300, schools, healthcare facilities without surgery or emergency treatment). Risk Category IV covers essential facilities (hospitals, fire stations, emergency operations centers). The Risk Category determines which wind speed map to use (ASCE 7 Figures 26.5-1A through 26.5-1D in the 2022 edition), the seismic importance factor, and the snow importance factor.
Plan reviewers check the Risk Category shown on the structural cover sheet against the building's stated occupancy on the architectural code analysis. The most common error is a mixed-use building (e.g., ground-floor retail with apartments above) where the structural engineer used Risk Category II but the building includes a Risk Category III occupancy (such as a daycare or assembly space over 300). The entire building must be designed for the highest applicable Risk Category unless the different occupancies are separated by structural independent elements.
Wind speed parameters
ASCE 7-22 Chapter 26 requires the following wind design parameters to be shown on the structural drawings or in the design criteria: basic wind speed (V) from the appropriate map for the Risk Category, wind directionality factor (Kd), exposure category (B, C, or D), topographic factor (Kzt), ground elevation factor (Ke), and the internal pressure coefficient (GCpi) including whether the building is classified as enclosed, partially enclosed, or partially open.
| Parameter | ASCE 7-22 reference | Common error |
|---|---|---|
| Basic wind speed (V) | Figures 26.5-1A through 1D | Using the wrong map for the Risk Category, or using ASCE 7-16 speeds with 7-22 load factors |
| Exposure category | Section 26.7 | Defaulting to Exposure C on a suburban site that qualifies as Exposure B based on surrounding terrain |
| Topographic factor (Kzt) | Section 26.8 | Leaving Kzt = 1.0 on a site near an escarpment or ridge without documenting why the topographic speed-up effect doesn't apply |
| Enclosure classification | Section 26.12 | Classifying a building with large openings (loading docks, overhead doors) as enclosed instead of partially enclosed |
| Internal pressure (GCpi) | Table 26.13-1 | Using +/-0.18 (enclosed) when the building should be classified as partially enclosed (+/-0.55) |
The exposure category is one of the most frequently contested parameters. Section 26.7 defines Exposure B as urban and suburban areas with closely spaced obstructions, Exposure C as flat open terrain, and Exposure D as flat unobstructed areas adjacent to large bodies of water. The exposure is determined based on the upwind surface roughness for each wind direction. Many engineers conservatively default to Exposure C, which is acceptable but may result in unnecessarily higher design loads. Conversely, claiming Exposure B on a site adjacent to open farmland or a large parking lot will trigger a reviewer comment asking for justification.
Seismic design errors
Site class determination
ASCE 7 Section 11.4.3 requires a site class assignment (Site Class A through F) based on soil properties in the upper 100 feet. Site Class D (stiff soil) is the default when soil data is not available, per Section 11.4.3. Plan reviewers check the structural drawings for the stated site class and compare it to the geotechnical report (if provided). The most common error is claiming Site Class B or C without a geotechnical investigation to support it. If no geotechnical data is available, the engineer must use Site Class D (or Site Class E for sites where soft clay conditions are known or suspected). Some jurisdictions require a geotechnical report for all projects, while others allow the default Site Class D without investigation.
Seismic Design Category determination
The Seismic Design Category (SDC) is determined from ASCE 7 Tables 11.6-1 and 11.6-2 based on the mapped spectral acceleration parameters (SDS and SD1), the Risk Category, and the site class. The SDC must be the more severe of the two table assignments (one based on SDS, one based on SD1). Plan reviewers verify the SDC by checking the mapped spectral accelerations from the USGS Seismic Design Maps tool, applying the site coefficients for the stated site class, computing SDS and SD1, and looking up the SDC in both tables. Common errors include using the wrong site coordinates for the USGS lookup (especially for projects near the boundary between seismic zones), applying incorrect site coefficients for the stated site class, and taking the SDC from only one table instead of the more severe of both.
Seismic force-resisting system selection
ASCE 7 Table 12.2-1 lists the permitted seismic force-resisting systems (SFRS) and their associated design coefficients: response modification coefficient (R), deflection amplification factor (Cd), and overstrength factor (Omega-0). The table also restricts which systems are permitted in each SDC and sets height limits. Plan reviewers check that the SFRS identified on the structural drawings is permitted for the project's SDC and does not exceed the applicable height limit. The most common error is selecting a system with height limitations that the building exceeds (for example, ordinary steel moment frames are limited to 65 feet in SDC D), or using the wrong R value for the system actually detailed on the drawings. If the structural drawings show braced frames but the connections are not detailed for the ductility requirements of Special Concentrically Braced Frames, the R value for an Ordinary system must be used, which significantly increases the design base shear.
Load combinations
ASCE 7 Section 2.3 (LRFD) and Section 2.4 (ASD) define the load combinations. Plan reviewers check that the design criteria on the structural drawings reference the correct load combinations and that all applicable loads are included. Common errors include omitting the overstrength factor (Omega-0) from combinations required by Section 12.4.3 for SDC B through F (collector elements, column splices, and certain foundation connections require amplified seismic loads), and using ASCE 7-16 load combinations with ASCE 7-22 mapped loads without adjusting for the differences in how the two editions handle multi-period design spectra. The 2022 edition introduced a multi-period response spectrum that can change the design forces compared to the two-period approximation used in ASCE 7-16, especially for tall buildings or buildings with long fundamental periods.
Missing information on drawings
Design criteria summary
The structural cover sheet or general notes must include a complete set of design criteria. ASCE 7 Section 1.4 requires the design loads and load combinations to be shown on the construction documents. For wind design, this means the basic wind speed, exposure category, enclosure classification, topographic factor, and internal pressure coefficient. For seismic design, this means the mapped spectral acceleration parameters (Ss and S1), site class, site coefficients (Fa and Fv), SDS and SD1, Risk Category, Seismic Design Category, SFRS type with R, Cd, and Omega-0 values, and the fundamental period. Reviewers reject submittals that omit these parameters because they cannot verify the design without them. A complete design criteria summary on the cover sheet prevents the most common "information request" comments and speeds up the review.
Drift limits and deformation compatibility
ASCE 7 Table 12.12-1 sets story drift limits based on the building type and Risk Category. For most structures in Risk Category II, the allowable story drift is 0.02 times the story height. For Risk Category IV, the limit drops to 0.01 times the story height. Plan reviewers check for a drift analysis or drift summary on the structural drawings showing that the computed story drift (amplified by Cd) does not exceed the allowable drift at each story. For buildings in SDC D through F, Section 12.12.5 also requires deformation compatibility checks for structural members not part of the SFRS to confirm they can accommodate the expected lateral deformations without losing gravity load-carrying capacity. Missing drift analyses and missing deformation compatibility checks are common plan review comments on mid-rise and high-rise projects.
Catching these before submittal
Wind and seismic design parameter errors are particularly expensive to fix after submittal because they affect the entire structural design, not just one detail or one member. If the SDC changes from C to D, the connection detailing requirements change for every moment frame and braced frame connection in the building. If the wind exposure changes from B to C, every cladding attachment, roof deck fastening, and lateral frame design must be rechecked. Catching these parameter-level errors before submittal, before the reviewer pulls out the USGS tool and the ASCE 7 tables, saves the most expensive resubmittal cycle in structural design.