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2010 ADA Standards for Accessible Design Pocket Guide

104 Conventions

Dimension lines show English units above the line (in inches unless otherwise noted) and the SI units (in millimeters unless otherwise noted). Small measurements show the dimension with an arrow pointing to the dimension line. Dimension ranges are shown above the line in inches and below the line in millimeters. Min refers to minimum, and max refers to the maximum. Mathematical symbols indicate greater than, greater than or equal to, less than, and less than or equal to. A dashed line identifies the boundary of clear floor space or maneuvering space. A line with alternating shot and long dashes with a c and l at the end indicate the centerline. A dashed line with longer spaces indicates a permitted element or its extension. An arrow is to identify the direction of travel or approach. A thick black line is used to represent a wall, floor, ceiling or other element cut in section or plan. Gray shading is used to show an element in elevation or plan. Hatching is used to show the location zone of elements, controls, or features. Terms defined by this document are shown in italics.

Figure 104 Graphic Convention for Figures

104.1 Dimensions.

Dimensions that are not stated as “maximum” or “minimum” are absolute.

104.1.1 Construction and Manufacturing Tolerances.

All dimensions are subject to conventional industry tolerances except where the requirement is stated as a range with specific minimum and maximum end points.

ETA Editor’s Note:

For additional information go to ADA Tolerances - Additional Resources or keyword search "Tolerance." 

Advisory 104.1.1 Construction and Manufacturing Tolerances. Conventional industry tolerances recognized by this provision include those for field conditions and those that may be a necessary consequence of a particular manufacturing process. Recognized tolerances are not intended to apply to design work.

It is good practice when specifying dimensions to avoid specifying a tolerance where dimensions are absolute. For example, if this document requires “1½ inches,” avoid specifying “1½ inches plus or minus X inches.”

Where the requirement states a specified range, such as in Section 609.4 where grab bars must be installed between 33 inches and 36 inches above the floor, the range provides an adequate tolerance and therefore no tolerance outside of the range at either end point is permitted.

Where a requirement is a minimum or a maximum dimension that does not have two specific minimum and maximum end points, tolerances may apply. Where an element is to be installed at the minimum or maximum permitted dimension, such as “15 inches minimum” or “5 pounds maximum”, it would not be good practice to specify “5 pounds (plus X pounds) or 15 inches (minus X inches).” Rather, it would be good practice to specify a dimension less than the required maximum (or more than the required minimum) by the amount of the expected field or manufacturing tolerance and not to state any tolerance in conjunction with the specified dimension.

Specifying dimensions in design in the manner described above will better ensure that facilities and elements accomplish the level of accessibility intended by these requirements. It will also more often produce an end result of strict and literal compliance with the stated requirements and eliminate enforcement difficulties and issues that might otherwise arise. Information on specific tolerances may be available from industry or trade organizations, code groups and building officials, and published references.

104.2 Calculation of Percentages.

Where the required number of elements or facilities to be provided is determined by calculations of ratios or percentages and remainders or fractions result, the next greater whole number of such elements or facilities shall be provided. Where the determination of the required size or dimension of an element or facility involves ratios or percentages, rounding down for values less than one half shall be permitted.

104.3 Figures.

Unless specifically stated otherwise, figures are provided for informational purposes only.


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