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ADA Tolerances and Acceptable Measurements

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This course will cover the specific wording of ADA Standards Section 104.1.1 on tolerances and similar language in selected other accessibility standards and explain how they should be interpreted. It will cover what types of conditions are subject to the tolerances language and which ones are not. The panelists will discuss how they measure field conditions affecting accessibility and ADA compliance, how those measurements are critical in understanding and applying the tolerances language, and what types of field conditions affect the determination of whether a measurement is within the tolerances. This session provides architects with peer feedback on a critical but highly esoteric topic.

Course expires 1/6/2025

Learning Objectives


Understand how to analyze and apply ADA and other accessibility tolerance language where it is different from building code tolerance language.      


Know where to find additional resources to assist you when you need to determine whether a field condition on a project falls within ADA tolerances.


Measure many of the field conditions where arguments often arise about what is and is not within ADA tolerances.


Gain a holistic approach to minimizing risk and maximizing compliance with ADA standards.

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James L.E. Terry, AIA, CASp is CEO of Evan Terry Associates and has specialized in ADA compliance and accessible design for the last 23 years. Mr. Terry has worked with public entities, private corporations (including 9 of the Fortune 20), the U.S. Congress, the Administrative Office of the U.S. Courts, and federal agencies (including the Department of Justice, the Access Board, the Social Security Administration, the Department of Transportation, and others). He has led Evan Terry Associates in writing 15 books and software programs on the ADA and state access standards facilities compliance and universal design. Mr. Terry has testified about Construction Tolerances and Acceptable Measurements in several state and national ADA lawsuits and has worked on projects involving the US Department of Justice where Construction Tolerances had to be applied. He is a member of the Board of Directors of the National Association of ADA Coordinators.

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Bill is a graduate of LSU and an architect (Colorado, Alabama, Louisiana & Georgia Licenses) specializing in facility access compliance. He began working in this area of expertise while at Evan Terry Associates, Inc. just after the ADA was passed in 1990. He has extensive experience in ADA and Fair Housing Act litigation and since 1994 has been one of a handful of architect expert witnesses retained on behalf of the US Department of Justice in ADA and FHA investigations and law suits. He was a defense expert for the California Department of Transportation and the City and County of Honolulu in major ADA curb ramp litigation and testified for the defense at the 2011 ADA trial against the City and County of San Francisco. He was a member of the US Access Board's Public Rights-of-Way Accessibility Advisory Committee and consults extensively on facility compliance issues around the nation.

For many years he as been an Instructor in the Office of Executive Education at Harvard University's Graduate School of Design conducting workshops alongside Jim Terry, AIA on ADA and Fair Housing Act issues during summer sessions.

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More than 30 years ago, Mr. Mazz started his accessibility career with the University of Maryland's Section 504 Transition Plan. Since then, he has been responsible for the accessibility projects in his private practice and in the offices of Edwin F. Ball, AIA and Celentano Esposito & Associates. Also, Mr. Mazz has collaborated with other nationally known "accessibility firms" including Ron Mace and Barrier Free Environments. His major clients have included the Architect of the Capitol, other Federal agencies, and Howard County Public School System, housing developers and architects. In his eight years with the Federal Government, Mr. Mazz was an architect in DOJ’s Housing and Civil Enforcement and Disability Rights Sections and the senior advisor on accessibility issues in HUD’s Office of Fair Housing and Equal Opportunity. More than 70% of his career has focused on accessibility.

For the past 13 years, Mr. Mazz has focused exclusively on the Americans with Disabilities Act (ADA), the Fair Housing Amendments Act (FHA), Section 504 of the Rehabilitation Act, the Architectural Barriers Act (ABA), and accessible design issues. Prior to federal employment, he belonged to several disability organizations and donated services through the Spinal Cord Injury Network of Metropolitan Washington and Independence Now, Inc. He continues to donate services through the Maryland Disability Law Center. Additionally, Mr. Mazz is a board member of CALMRA, a community based residential service provider for adults with cognitive disabilities.

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David Ballast, FAIA, CSI, NCARB, NCIDQ is the author of Handbook of Construction Tolerances, 2nd ed. and has consulted with the Access Board to attempt the development of industry standard construction tolerances to which ADAAG can refer. Mr. Ballast completed a research project for the Transportation Research Board of the National Academy of Sciences to study and recommend suggested tolerances for right-of-way construction. Mr. Ballast has also provided expert witness consulting in the area of construction tolerances.

He is the author of numerous magazine articles and 16 books including four volumes of study guides for the Architect Registration Examination. Other books include Interior Design Reference Manual, A Guide to the NCIDQ Exam, Interior Construction and Detailing for Designers and Architects, The Encyclopedia of Associations and Information Sources for Architects, Designers, and Engineers, and the Architect’s Handbook of Construction Detailing, 2nd ed.

Mr. Ballast holds a Bachelor of Architecture degree with special honors (1971) from the University of Colorado and has over 35 years of experience in the architectural and interior design professions. He is owner of Architectural Research Consulting, a consulting firm offering applied research, technical advice, specifications, and information management services to architects, interior designers, and others in the construction industry.