What's the story with truncated domes?

That is the million-dollar question most frequently asked so far this year! 

Owners, managers and contractors are up in arms over the new truncated dome spacing call out in the new 2013 California Building Code and they want answers!

Truncated Dome

Many of these property owners have had their contractors install truncated domes on curb ramps and path of travel crossings recently and are now being told that these truncated dome panels do not meet State of California Building Code for dome-to-dome spacing.

To make matters worse, the 2010 CBC (previous code) required truncated domes the entire width and length of the curb ramp excluding the wings. What this did was double the amount of truncated dome panels needed on curb cut ramps here in California, which just so happened to exhibit the incorrect dome spacing.

Here is a historical snap shot of the detectable warning truncated dome from the stand point of Federal design, ICC ANSI and State of California design.In 2010 the Federal ADA standards changed and no longer required truncated domes for Title 3 (private commercial properties) on curb ramps, path of travel crossings and smooth transition areas between accessible walkways and the vehicular way!

California did not remove this requirement but has changed the panel size requirements for curb cut ramps starting in 2010.

But even before the Feds removed the requirement of t-domes on private property, the spacing dimensions for t- domes were different outside of California.

A history of Federal truncated dome size & spacing:

1991 Federal Code - nominal 0.9" dia., nominal 0.2" ht., nominal 2.35" center-to-center spacing.

2010 Federal Code - 0.9" to 1.4" base dia., top dia. - 50% to 65% of base dia., 0.2" ht., 1.6" to 2.4" center-to-center spacing and 0.65" min. base-to-base spacing measured between the most adjacent domes on a square grid.Let’s just go back three code cycles in California and look at the exact wording for truncated domes.A history of California truncated dome size and spacing:

2007 CBC - nominal 0.9" base dia. tapering to 0.45" at top, nominal 0.2" ht., nominal 2.35" center-to-center spacing complying w/ fig. 11B-23A (domes shown staggered), only DSA-AC detectable warning products shall be installed.

2010 CBC - nominal 0.9" base dia. tapering to 0.45" at top, nominal 0.2" ht., nominal 2.35" center-to-center spacing complying w/ fig. 11B-23A (2 domes shown vertical), only DSA-AC detectable warning products shall be installed.

2013 CBC - 0.9" to 0.92" base dia., 0.45" to 0.47" top dia., 0.18" to 0.22" ht., 2.3" to 2.4" center-to-center spacing and 0.65" min. base-to-base spacing measured between the most adjacent domes on a square grid (figure 11B-705.1 shows horizontal & vertical dim. of 2.3-2.4 from center-to-center of dome in square grid pattern). Exception for t.domes in a radial pattern allow for center-to-center spacing of 1.6" to 2.4".A history of American National Standards truncated dome size and spacing:

2003 ICC A117.1 - 0.9" to 1.4" base dia., top dia. - 50% to 65% of base dia., 0.2" ht., 1.6" to 2.4" center-to-center spacing and 0.65" min. base-to-base spacing measured between the most adjacent domes on a square grid.

2009 ICC A117.1 - 0.9" to 1.4" base dia., top dia. - 50% to 65% of base dia., 0.2" ht., 1.6" to 2.4" center-to-center spacing and 0.65" min. base-to-base spacing measured between the most adjacent domes on a square grid.

There has been constant confusion and difference of opinion on this one item for years and it has finally come to a head. 

Now for the first time, California building departments are cracking down on this product and the inspectors are really looking at the wording in the codes closer than ever.

An unintended consequence of this is the “ADA activist” industry is focusing in on this and we are seeing an increase in claims involving the spacing of the domes. These activists and their attorneys claim that it is a barrier within itself for wheelchair users as well as other disabled persons trying to push shopping carts over these narrowly spaced domes.

Couple this with the fact that city/county inspectors are “failing” contractor’s final inspections due to improper dome spacing panels being used, we have a potentially huge problem here in California.

It used to be that a disabled person could only sue for barriers that affected their specific disability. So only a sight-impaired person could call out the lack of or improper installation of truncated domes.

Now, any number of mobility impaired persons can claim that these non-California style domes are in essence a “barrier” and add this item to the list of other barriers such as excessive surface slope in the disabled stall and loading zone area or lack of proper ratio of “Van Accessible” stalls that they find on a property.

Of course this “million-dollar” question sparked multiple additional questions and concerns to consider as we move forward with helping our clients bring a higher level of accessibility to their properties.

As the powers to be in California deal with this issue, I will keep you up to date and let you all know how to safely move forward in this ever-changing environment.

If you have any questions regarding this issue please don't hesitate to contact me directly.