Concrete Detectable Warning Surface

By Bruce Woolner

One of the first concepts utilized to create detectable warning surfaces was to form truncated domes out of the wet concrete with a stamp. Stamps have been created to form other patterns in the concrete such as striations and brick patterns with varying degrees of success. Stamps can work well in creating indentations in the surface such as grooves but it is much more difficult to create protuberances above the level of the concrete.

Some factors working against the formation of the domes in a concrete detectable warning surface are gravity, the nature of wet concrete wanting to stick to the surface of the stamp and the precise measurements of the domes in the regulations. From informal observations throughout the country, the success rate of forming compliant domes would be around 1%. As far as the contractor is concerned, success may be determined by the acceptance of the job by local inspectors. As time passes, the inspectors become stricter in their evaluations due to legislative pressure. This applies to many aspects of the construction of the sidewalks, particularly the measurement of slopes, which are being held within very tight limits.

The requirement of color contrast is another challenge when concrete is used as a detectable warning surface. A truckload of colored concrete is not that practical logistically as it can only be used on the ramp surface which is a very small area causing it to be spread among several ramps and intersections.

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