Table 6.21 – Thresholds at Doors
Current Guidelines:  
4.13.8  Thresholds at Doorways.  Thresholds at doorways shall not exceed ¾ in (19 mm) in height for exterior sliding doors or ½ in (13 mm) for other types of doors.  Raised thresholds and floor level changes at accessible doorways shall be beveled with a slope no greater than 1:2 (see 4.5.2).  

[Note:  Section 4.5.2 requires changes in level between ¼ inch and ½ inch to be beveled with a slope not steeper than 1:2.]  
 
Final Revised Guidelines:  
404.1 General.  Doors, doorways, and gates that are part of an accessible route shall comply with 404.

404.2.5 Thresholds.  Thresholds, if provided at doorways, shall be ½ inch (13 mm) high maximum.  Raised thresholds and changes in level at doorways shall comply with 302 and 303.
EXCEPTION:  Existing or altered thresholds ¾ inch (19 mm) high maximum that have a beveled edge on each side with a slope not steeper than 1:2 shall not be required to comply with 404.2.5.

Model Codes & Standards
IBC 2000:  Section 1003.3.1.6 has an equivalent requirement for thresholds at doorways that are part of an accessible means of egress, except for sliding doors.  Section 3408.7.14 has an equivalent exception for existing or altered thresholds. 

IBC 2003:  Section 1008.1.6 has an equivalent requirement for thresholds at doorways that are part of an accessible means of egress, except for sliding doors.  Section 3409.7.12 has an equivalent exception for existing or altered thresholds. 

ICC/ANSI A117.1-1998:  Section 404.2.5 has an equivalent requirement for thresholds at doorways.  Section 1002.5 has an equivalent requirement for thresholds at doorways in Type A dwelling units, except for exterior sliding doors.