A building official on a new construction project that we were consulting for raised a question regarding where to measure the handrail extension at the top of a stair. ADA section 505.10 calls for a 12 inch handrail extension at the top of stairs beyond the stair nosing or beyond the beginning/end of a ramp run.  A similar extension is required at the bottom of stairs, except that the handrail at the bottom of a stair is required to extend the length of one tread at the angle of the stair.  But regardless, the technical question pertains to where on the handrail you should measure as it turns horizontally toward a wall return, or as it turns downward to a guard/post or down to the floor. 

Up until this review, we had not taken a strict reading of the language, but had measured from the stair nosing to any part of the handrail that extended 12" whether it was for a stair or a ramp.  So we set about analyzing the precise wording of the 2010 ADA sections. 

For the short answer, jump to our Conclusion and open the attached PDF sketches for reference. For the rationale behind our review, please read the following Detailed Analysis.

The wording in section 505 of the 2010 ADA Standards significantly clarified the intent of the 1991 Standards and leaned strongly on the wording established in the ICC/ANSI A117.1-2003. 

Three key phrases stood out in the reading of section 505, specifically in sections 505.10, 505.10.2 (and sub-points .1, .2 and .3) and 505.6. Each of these three phrases helped us refine our understanding of the intent in order to design and to evaluate handrail extensions.  Open the attached PDF file showing 3 conditions of handrail extensions and the variety of measuring points.

Phrase 1.  IN THE SAME DIRECTION:

505.10 Handrail Extensions.

Handrail gripping surfaces shall extend beyond and in the same direction of stair flights and ramp runs in accordance with 505.10.       [emphasis added, typical]

The phrase "in the same direction of" the stair flights or ramp runs simply means in the direction of the normal pedestrian flow up/down the stairs or ramp.  Thus, should the handrail extension return to the wall to terminate, the point where the radius begins is the point where it no longer extends in the same direction.  This is shown as Dimension D in Sketch A of the attached PDF.

Phrase 2. SHALL EXTEND HORIZONTALLY:

505.10.1 Top and Bottom Extension at Ramps.

Ramp handrails shall extend horizontally above the landing for 12 inches (305 mm) minimum beyond the top and bottom of ramp runs.

505.10.2 Top Extension at Stairs.

At the top of a stair flight, handrails shall extend horizontally above the landing for 12 inches (305 mm) minimum beginning directly above the first riser nosing. Extensions shall return to a wall, guard, or the landing surface, or shall be continuous to the handrail of an adjacent stair flight.

Where ramp and stair extensions are called to "extend horizontally" it means just that: horizontal. Therefore at the point that a handrail starts to turn downward to a post, to a guard, or to the floor, it is no longer horizontal.  And that would be the point to measure from the stair nosing or the top/bottom of the ramp.  See Dimensions D in the attached Sketches B and C.

505.10.3 Bottom Extension at Stairs

At the bottom of a stair flight, handrails shall extend at the slope of the stair flight for a horizontal distance at least equal to one tread depth beyond the last riser nosing. Extension shall return to a wall, guard, or the landing surface, or shall be continuous to the handrail of an adjacent stair flight.

A variation of the "horizontal" phrase is when the plane of the handrail extension is parallel to the slope of the stair flight and extends an extra tread from the bottom nosing.  The same precedent would apply: measure to the point when the handrail stops being at the same slope of the stair flight.  This is particularly relevant when the angled handrail turns downward to a post or the floor.  If the handrail returned to the wall, the measuring point would be where the handrail stops being "in the same direction" of the stair flight.

Phrase 3:  SHALL NOT BE OBSTRUCTED ALONG THEIR TOPS OR SIDES:

505.6 Gripping surface.

Handrail gripping surfaces shall be continuous along their length and shall not be obstructed along their tops or sides. The bottoms of handrail gripping surfaces shall not be obstructed for more than 20 percent of their length. Where provided, horizontal projections shall occur 1½ inches (38 mm) minimum below the bottom of the handrail gripping surface.

This last criteria should echo the "in the same direction" criteria for extensions returning to the wall.  It is based on the concept of the return to the wall no longer allowing the continuous unobstructed gripping surface along the top and sides of the handrail.  The result is that where the extension begins to curve away from the direction of travel, the handrail becomes obstructed.  It would be to that point that the extension length would be measured to the bottom tread and should be roughly the same point similar to Dimension D and on Sketch A.

In simpler language, for handrail extensions at the top and bottom of stair flights and ramp runs, the measurement is taken from the nosing of the stair or the end of the ramp run to the start of the return radius. The return radius begins at a point in which the extension no longer extends horizontally or in the same direction as the stair or the ramp run.

CAUTIONS:

1] Be aware that some states have a different dimension, particular at the bottom of the stair (California is one example which still requires the angled extension to continue one tread's worth plus an additional 12" horizontal portion).  

2] Per 210.1 Stairways, General
Exception 2, In alterations, stairs between levels that are connected by an accessible route shall not be required to comply with 504, except that handrails complying with 505 shall be provided when the stairs are altered.        [emphasis added]

3] Also recall that some existing stair handrails are safe harbored under 36.304(d)(2) - Barrier Removal, 306.403(a)(2) - Alterations, 35.150(b)(2) - Existing Facilities (program access), and 35.151(b) - Alterations Path of Travel.