The Seismic Requirements You Need to Meet Before Building

Analyst Insight: Before a single delivery hits the warehouse floor, there’s a critical step that many facilities overlook: Confirming what local codes, seismic requirements and load conditions actually demand for racking. Skipping this stage can result in costly redesigns, project delays and even unsafe installations.

For logistics managers and facility planners, understanding when seismic ratings, slab analyses or professional engineer (PE) stamps are necessary is essential.

Many assume that seismic racking requirements are only relevant in California or other earthquake-prone states. In reality, seismic hazards exist across the U.S. The New Madrid Seismic Zone affects parts of Missouri, Arkansas and Tennessee, while Charleston, South Carolina has its own notable seismic history. Modern building codes have replaced simple zone numbers with seismic design categories (SDCs) ranging from A through F, reflecting precise hazard levels at each building site. Even moderate zones are seeing stricter enforcement.

Facility managers can quickly check their site’s seismic risk using free tools. The American Society of Civil Engineers Hazard Tool, USGS design maps, and SeismiCat provide the same data that engineers reference when determining SDC, soil classification and peak ground acceleration. This helps teams know whether a PE should be involved before a single rack is ordered.

Rack design in seismic areas is mandated by codes such as the International Building Code and American National Standards Institute MH16.1. The latter requires racks over eight feet tall or free-standing to account for seismic forces. The Federal Emergency Management Agency’s foundational report on rack design in seismic regions outlines proper configuration, which has informed subsequent building codes and standards. Simply specifying general structural steel or welding standards (such as the American Society for Testing and Materials A36, A572, or American Welding Society D1.1) does not ensure seismic compliance. Each standard has a seismic-specific companion, such as ANSI/American Institute of Steel Construction 341-22 for steel buildings or AWS D1.8 for welding, that engineers must explicitly invoke.

A PE stamp is not optional in high-seismic areas. Local building departments or fire marshals will require calculations and drawings stamped by a licensed engineer. Without them, installations can be red-tagged, forcing costly dismantling or upgrades. Typical PE stamping costs are but a fraction of the expense and disruption of correcting a non-compliant system after installation.

SDCs D, E, and F require engineered racking. Hardware requirements are strict: base plates may need to measure from 5”×5” up to 6”×8”; anchors must accommodate seismic forces, and poorly secured racks are a common cause of cascade failures. The International Code Council’s SDC map tool helps managers cross-reference addresses against local codes, ensuring design compliance before installation.

Soil type can dramatically affect seismic performance. Soft or liquefiable soils amplify vibrations, increasing stress on foundations. Slab thickness, concrete strength, soil bearing pressure and reinforcement layout are all parameters a PE will consider. Even a slab sufficient for vehicle traffic can fail under concentrated rack loads, since point loads from upright legs exceed the distributed weight of forklifts. Core testing, ground-penetrating radar or reviewing as-built documentation is critical, particularly for older facilities. Resources from the American Concrete Institute and American Society of Concrete Contractors offer guidance on slab assessment and testing.

There’s a lot to understand and check in order to ensure your storage and racking is compliant with seismic and other regulations. Here’s a few practical steps to get started:

• Check seismic risk early. Use online tools to determine your site’s SDC and identify soil classification.
• Determine whether a PE stamp is required. Engage a licensed engineer early to avoid inspection delays.
• Verify slab capacity. Conduct concrete core tests, GPR scans, or consult historical as-built documents.
• Specify standards and their seismic companions. Ensure engineers explicitly apply ANSI/AISC 341, AWS D1.8, and other seismic-relevant codes.
• Plan base plates and anchors with seismic forces in mind. Pay attention to edge distances and joint proximity.

Compliance matters more than ever before. Loads are getting heavier, racks are taller, and storage density is increasing, particularly with automated storage and retrieval systems. For example, a 120-foot-tall AS/RS can carry over 150,000 pounds, placing significant stress on slabs and soil. Compliance checks once considered optional are now essential prerequisites.

Understanding seismic requirements, slab capacities, and PE stamping is a risk-management strategy that protects people, property, equipment. and productivity. By approaching racking projects with the right information, facility managers can build safer, more resilient operations while avoiding any costly surprises.