ADAAG Manual

Character Height [4.30.3]

Characters must be sized according to the viewing distance although a minimum 3 inch upper case or capital letter height is required for overhead signs (i.e., above 80 inches for adequate headroom).

Recommendations: Both the horizontal and vertical viewing distance should be considered. The viewing location upon which calculations are based may be difficult to pinpoint in long corridors and large rooms. SEGD recommends a minimum 75 feet viewing distance for such areas. Traffic patterns and sign function may also be important factors to consider. Consider a minimum 1 inch cap height for every 25 feet of viewing distance (horizontal) with 5/8 inch the minimum as recommended by SEGD. Further guidance is also available from the CABO/ANSI A117.1‒1992 standard which recommends heights based on the mounting height (1 inch minimum height for signs mounted from 48 to 60 inches above the floor and a 2 inch minimum for those above 60 and below 80 inches).