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1991 ADA Standards for Accessible Design

Note: This document, portion of document or referenced document was published prior to the 2010 ADA Standards, and is still applicable.

4.9.3 Nosings.

The undersides of nosings shall not be abrupt. The radius of curvature at the leading edge of the tread shall be no greater than 1/2 in (13 mm). Risers shall be sloped or the underside of the nosing shall have an angle not less than 60 degrees from the horizontal. Nosings shall project no more than 1‒1/2 in (38 mm) (see Fig. 18).

Side elevation showing a flush riser with minimum usable tread width and maximum nosing radius.

Fig. 18 Usable Tread Width and Examples of Acceptable Nosings

Side elevation showing angled nosing with maximum nosing angle and radius.

Fig. 18 Usable Tread Width and Examples of Acceptable Nosings

Side elevation showing rounded nosing with maximum nosing angle and radius.

Fig. 18 Usable Tread Width and Examples of Acceptable Nosings

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