Guidance on the 2010 ADA Standards for Accessible Design

104 Conventions

Dimensions. Section 104.1 of the 2010 Standards notes that dimensions not stated as a “maximum” or “minimum” are absolute. Section 104.1.1 of the 2010 Standards provides that all dimensions are subject to conventional industry tolerances except where the requirement is stated as a range with specific minimum and maximum end points. A commenter stated that the 2010 Standards restrict the application of construction tolerances only to those few requirements that are expressed as an absolute dimension.

This is an incorrect interpretation of sections 104.1 and 104.1.1 of the 2010 Standards. Construction and manufacturing tolerances apply to absolute dimensions as well as to dimensions expressed as a maximum or minimum. When 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 finished floor, that range provides an adequate tolerance. Advisory 104.1.1 gives further guidance about tolerances.

Section 104.2 of the 2010 Standards provides that 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 is permissible.

A commenter stated that it is customary in the building code industry to round up rather than down for values less than one-half. As noted here, where the 2010 Standards provide for scoping, any resulting fractional calculations will be rounded to the next whole number. The Department is retaining the portion of section 104.2 that permits rounding down for values less than one-half where the determination of the required size or dimension of an element or facility involves ratios or percentages. Such practice is standard with the industry, and is in keeping with model building codes.