Welcome to ATC-20:

Your Guide to Postearthquake Safety Evaluation of Buildings

What is ATC-20? 

ATC-20, or the Postearthquake Safety Evaluation of Buildings, is a widely recognized guideline designed to ensure the evaluation for safety and usability of buildings in the aftermath of an earthquake. This systematic approach assists building inspectors, engineers, and professionals in swiftly and effectively evaluating structures to determine if they are safe for occupancy.


ATC-20 Building Classification

The ATC-20 guideline provides a structured, step-by-step process for assessing buildings after an earthquake. The process begins with a visual screening and can progress to more detailed evaluations as necessary. The focus is on identifying potential hazards and structural damage that may have occurred during the earthquake. This evaluation includes assessing foundations, structural systems, non-structural elements, and site conditions.

Based on the evaluation, buildings are typically categorized into three groups:

Green Tag: Buildings safe for occupancy with little to no damage.

Yellow Tag: Buildings with moderate damage, possibly requiring repairs before full access.

Red Tag: Buildings unsafe for occupancy due to severe damage or potential collapse.

The ATC-20 guideline provides specific criteria and guidelines for assigning these tags based on observed conditions and damage. The guideline is widely used by building officials, engineers, and emergency management organizations to safeguard lives following an earthquake.

Important Note

Although ATC-20 is invaluable for initial evaluations, it is not a substitute for a comprehensive structural assessment by a qualified structural engineer. The guideline identifies visible damage and safety concerns but may not capture all potential structural issues. Therefore, it is advisable to follow the initial evaluation with a detailed assessment by a professional engineer to determine a building's long-term structural integrity.

ATC-20 Certification

To conduct postearthquake safety evaluations following ATC-20 guidelines, individuals must be certified through an official FEMA partner like the Utah Division of Emergency Management or the Utah Seismic Safety Commission. Individuals may rely on their professional qualifications and experience in fields like engineering and architecture, but a professional background is not required. Training workshops, courses, or seminars covering the ATC-20 methodology and its application are offered for anyone interested in being part of the postearthquake safety evaluation team.

Specific requirements and certifications differ by location, so additional consulting with professional organizations, licensing boards, or local authorities may be required to gain the necessary qualifications for conducting postearthquake safety evaluations in your area.

Make Changes to Your Certification

To update your contact information, please contact:
John Crofts (Utah Earthquake Program Manager),

Request ATC-20 Certification Training

To request ATC-20 certification training, please contact the Utah Earthquake Program Manager, John Crofts,

For additional questions, please contact the USSC Safety Assessment Program Chair, Jim McClintic,

ATC-20 News

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