ASCE 7 is the foundation that every other structural code references. IBC Chapter 16 points to it for gravity, wind, seismic, snow, rain, flood, and ice loads. Get the loads wrong and everything downstream (member sizing, connection design, foundation capacity) is wrong with it.

Structural plan reviewers check load criteria early because it's the fastest way to find systemic problems. A single misclassified Risk Category cascades into incorrect load factors, drift limits, and redundancy requirements across the entire building. Here are the ASCE 7 issues that show up most consistently.

1. Risk Category and Importance Factor mismatches

ASCE 7 Table 1.5-1 assigns every building a Risk Category (I through IV) based on occupancy and use. The Risk Category then determines the Importance Factor for wind (Table 26.8-1), snow (Table 7.3-1), ice (Table 10.4-1), and seismic (Table 11.5-1) through the Seismic Design Category assignment.

The most common error: the general notes on the structural drawings list one Risk Category, but the load calculations use importance factors from a different category. This happens when the occupancy changes during design (a retail space becomes a daycare, bumping from Category II to III) and the structural notes aren't updated to match.

Cascading error
A wrong Risk Category doesn't just affect one number. It changes the basic wind speed (ASCE 7 Figure 26.5-1 has separate maps for each category), the ground snow load factor, the Seismic Design Category, and every load combination that includes those values. Plan reviewers check this first because it invalidates everything if it's wrong.

2. Wind exposure category errors

ASCE 7 Section 26.7 defines three surface roughness categories (B, C, D) and requires the designer to determine the Exposure Category based on upwind terrain. Exposure B is urban/suburban with closely spaced obstructions. Exposure C is open terrain with scattered obstructions. Exposure D is flat, unobstructed shoreline areas.

The error that reviewers catch: drawings that show Exposure B (the least demanding category) for a building that's clearly in open terrain, or a building near a large body of water that should be Exposure D. The difference between B and C can change wind pressures by 30-40%, which means undersized lateral systems and connections.

ASCE 7 Section 26.7.3 requires that the exposure be based on the ground surface roughness over a defined upwind fetch distance. Reviewers increasingly use aerial imagery to spot-check the exposure classification, especially for buildings at the edge of developed areas where the transition between B and C is ambiguous.

3. Missing or incorrect snow drift loads

ASCE 7 Section 7.7 through 7.9 requires drift loads at roof steps, parapets, and projections. Drift loads can easily exceed the balanced snow load, sometimes by a factor of two or more, and they're concentrated at the locations where roofs step down or where parapets create pockets for wind-deposited snow.

2-3x
drift surcharge vs. balanced snow load on a typical roof step

The most common omission: a multi-level building where the lower roof adjacent to a higher wall has no drift load shown on the structural drawings. The designer calculated the balanced roof snow load correctly but forgot (or chose not to show) the triangular drift surcharge per Section 7.7.1. Another frequent issue: leeward drift at parapets per Section 7.8, which is often missed on single-level buildings with tall parapets.

4. Seismic Design Category determined incorrectly

The Seismic Design Category (SDC) is assigned per ASCE 7 Section 11.6 based on the Risk Category and the mapped spectral response acceleration parameters (SDS and SD1). The SDC drives everything: which lateral systems are permitted, whether redundancy factors apply, detailing requirements, drift limits, and whether a geotechnical investigation is mandatory.

Common errors include: using the wrong site class (Section 11.4.3) because no geotechnical report was available and the designer assumed Site Class D without checking if the site actually has softer soils that would push it to E, or using pre-2016 spectral acceleration values from an earlier edition of the seismic maps rather than the values from the edition adopted by the local jurisdiction.

Site class matters more than most engineers expect
The difference between Site Class C and D can increase SDS by 15-20%. The difference between D and E can increase it by 30-50%. On a building near the SDC boundary (for example, between C and D), a site class error can change the entire lateral force-resisting system requirements.

5. Incomplete load path on drawings

ASCE 7 Section 1.3.1 requires a continuous load path from the point of load application to the foundation. This is a design philosophy requirement, not a calculation. The plan reviewer checks whether the drawings show how lateral forces transfer from the diaphragm to the shear walls or frames, from the walls/frames to the foundation, and from the foundation to the soil.

The most common gap: the drawings show the lateral system members (shear walls, braced frames, moment frames) but don't show the connections that transfer forces between them. Collector beams, drag struts, and diaphragm-to-wall connections are frequently missing from the drawings or shown without adequate detail. The members are sized correctly in the calculations, but the load path is incomplete on the construction documents.

6. Load combinations missing or using the wrong edition

ASCE 7 Section 2.3 (LRFD) and Section 2.4 (ASD) define the required load combinations. Each edition of ASCE 7 has slightly different combinations, and the combinations must match the edition adopted by the jurisdiction.

The error reviewers catch: structural calculations that use ASCE 7-22 load combinations in a jurisdiction that has adopted ASCE 7-16, or vice versa. The differences are subtle (ASCE 7-22 revised the treatment of flood loads in combinations, for example) but a reviewer who checks the general notes against the calculation cover sheet will catch the mismatch. Another common issue: omitting load combinations that include rain load (R), which is required per Section 8.3 for roofs with parapet or scupper drainage where ponding could occur.

7. Components and cladding pressures not shown

Designers calculate the Main Wind Force Resisting System (MWFRS) pressures for the overall building lateral design, but ASCE 7 Chapter 30 also requires separate Components and Cladding (C&C) pressures for individual elements: windows, wall panels, roof coverings, fascia, soffits, and equipment screens. C&C pressures are zone-dependent and can be two to three times higher than MWFRS pressures at roof corners and edges.

MWFRS
  • Overall building lateral loads
  • Chapter 27 or 28 pressures
  • Used for frames, shear walls, diaphragms
C&C
  • Individual element pressures
  • Chapter 30, zone-dependent
  • Used for cladding, glazing, roofing, fasteners

The issue: many structural drawing sets include MWFRS pressures on the general notes but omit C&C pressures entirely, or show C&C pressures only for the field zone (Zone 1) without the higher corner and edge zone pressures (Zones 2 and 3). The architect needs these numbers to specify glazing and cladding systems, and the plan reviewer needs to see them on the structural drawings to confirm the building envelope design basis.

How Callout checks ASCE 7 compliance
Callout reviews structural drawings against ASCE 7-22 and ASCE 7-16, checking for Risk Category consistency, drift load presence on stepped roofs, seismic parameter completeness, load combination correctness, and C&C pressure documentation. Each finding cites the specific ASCE 7 section and subsection so you can verify directly against the standard.