Ranges, Maximums minimums and tolerances in the 2010 ADA Standards

The ADA Standards has requirements of how tall, how low, how long elements should be for them to be usable for persons with disabilities. These ranges and limits are typically noted as either absolutes, maximums or minimums. This newsletter will explain why, as designers, it is not recommended to note the maximums and minimums in our drawings.

Here is a video that explains the concept. 

Door Maneuvering Clearance

One of the examples I want to discuss are door maneuvering clearances. Section 404 has requirements for clearance to open and go through the door using a wheelchair. The clearances listed in the section are noted as minimums, which implies that it is the lowest limit and should be larger than the number listed.

The figure above is the pull side approach which requires an 18″ MINIMUM clearance at the strike side of the door to pull the door open.

Our practice as design professionals is to note 18″ min. on the drawings or as a note, which will not provide construction tolerances. During my inspections, one of the common violations is when the door clearance is a few fractions of an inch less than the minimum required clearance.

The photo above shows a 17 1/2″ clearance at the latch side of the door not the MINIMUM 18″ due to construction mistakes or restrictions

Heights of Sinks and Lavatories

Per section 606 of the ADA, sinks and lavatories must be mounted so that the rim is no higher than 34″ a.f.f.

606.3 Height. Lavatories and sinks shall be installed with the front of the higher of the rim or counter surface 34 inches (865 mm) maximum above the finish floor or ground.

Many times, design professionals tend to use the 34″ a.f.f. as our dimension which again does not allow for any construction mistakes.

The drawing of the sink section shows all the dimensions as absolutes and does not allow for any construciton mistakes

The photo above shows a sink that is mounted higher than 34″ a.f.f.

Reach to operable parts

In section 308 and 309 the ADA provides guidelines on how high and how low the operable parts must be mounted. Design professionals, including electircal engineers, have a tendency to draw using the 48″ as a go by for elements.

The figure above is the ADA reach range for a forward approach. The reach is intended for operable parts and elements that we operate or use

The light switch above was mounted at 48 1/2″ a.f.f. which is higher than the minimum allowed reach.

Some electricians are taught that the 48″ is measuring the centerline of elements. At inspections I find that many switches are mounted 48″ to the center line of the junction box. The photo above shows a rocker switch which has its operable part at the top of the switch. It was mounted to the centerline which is not the operable part.

Tolerances in the ADA

The ADA does allow for tolerances, but it is vague in the allowable ranges for those.

ADA section 104.1.1 States:

“Construction and Manufacturing Tolerances. All dimensions are subject to conventional industry tolerances except where the requirement is stated as a range with specific minimum and maximum end points.”

Therefore if the figure has the words maximum and minimum or if it lists a range, The DOJ believes that the tolerances are already built in and industrustry standards for other tolerances may not be used.