The Mystery of Truncated Domes and ADA Requirements

Bigfoot, the loch ness monster, and truncated dome ADA requirements are three of the biggest mysteries known to mankind.  We are here to dispel the rumors and unlock the truth to these questions.  

In an effort to ensure compliance with detectable warning systems law, the governments on both federal and local levels have set measurable standards.  Truncated dome ADA requirements call for three key specifications.  Dome size, spacing and contrast are all measured to ensure compliance. 

Dome size is measured at the base, top and in height.  The dome base diameter is to be between .9” and 1.4”.  Top of the dome is to have a minimum of 50% and maximum of 65% of the base diameter.  Height requirements for each dome are exact at .2”. 

Spacing for domes is measured in two ways, center to center and base to base.  For two adjacent domes the center to center minimum is 1.6” and maximum is 2.4”.  With base to base requiring a spacing distance of .65”.

Contrast is defined as light on dark or dark on light.  This is measured by the detectable warning surface visually having a 70% color contrast from it surrounding area.  Contrast compliance can be enforced by a photographic light detector.    

Truncated dome ADA requirements are often misinterpreted, but dome compliance can be accomplished by knowing what to look for.  Dome size, spacing and contrast are the three requirements to remember. 

Now that we have uncovered the answers to the truncated dome mystery, there are two more to go.  Bigfoot lives in Springfield with a nice yeti and twins on the way.   Our    loch ness monster in a bold midnight move switched lakes and is planning his character reinvention. 

By Shawn Osborne

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