At California Truncated Dome Company, we guarantee that our work is compliant with both the Americans With Disabilities Act (ADA) and California Code. So, What exactly is the law regarding truncated domes in California?

According to the California Building Code (Chapters 11B-705.1 through to 11B-706), detectable warnings must consist of a surface embedded with truncated domes that meet the appropriate specifications in terms of color, size and spacing.

Dome size must meet the following guidelines:

  • Base diameter of between 22.9mm and 23.4mm

  • Top diameter of 11.4mm and 11.9mm

  • Dome height must be 5.1mm

Dome spacing must meet the following guidelines:

  • Center-to-Center Spacing must be between 58mm and 61mm

  • Base-to-Base Spacing must be a minimum of 16.5mm measured between adjacent domes on a square grid

  • Exceptions are made where a radial pattern is used, in which case the domes should have a center-to-center spacing of 41mm to 61mm

Color and contrast is also a key factor when installing truncated domes. California code does differ slightly to ADA guidelines in that it states all detectable warning surfaces must be yellow in color. There should be a minimum visual contrast of 70% between the detectable warning and the adjacent walking surface.


This represents only a brief summary of the law and regulations surrounding truncated domes. You can access a complete copy of the California Building Code HERE