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limiting threshold height to one-quarter inch for wheelchair access or cart traffic is a wonderful idea
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Over the past ten years, the Americans with Disabilities Act (ADA) has
been an increasingly important force in the architectural openings
industry. Building design has slowly evolved over the past decade to
include many elements that were not previously common to architectural
practice. Elements such as ramped entryways, automatic entrances, tactile
signage, and elevator access have become commonplace in today's building
designs. The architectural openings industry has adapted as well, with the
virtual elimination of doorknobs, and the growing demand for products such
as automatic operators, lever handles, ramped thresholds, and closers with
reduced opening force. Let's examine some of the components of an opening,
and what makes them important to accessibility and ADA compliance.
Starting at the floor, ADA states that changes in level up to 1/4 inch may be vertical without edge treatment. Changes in level between 1/4 inch and 1/2 inch must be beveled, with a slope no greater than 1:2. Changes in level greater than 1/2 inch must be accomplished by means of a ramp not exceeding 1:12 slope.
ADA also requires that thresholds not exceed 3/4 inch for exterior sliding doors, or 1/2 inch for other doors. This means that typical saddle-type thresholds up to one half inch in height are acceptable. These are the standard in the industry, but limiting the threshold height to one-quarter inch for areas that may require wheelchair access or cart traffic is a wonderful idea. It makes it slightly more difficult to adjust a door sweep to make perfect contact with the sloped edge of the threshold, but the decrease in threshold height makes wheeling anything through the opening much easier.
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