Curb Ramp Slope 10/19/2010
 
Just when you thought your curb ramp design/construction is right - think again!  TAS 4.7.2 requires compliance with 4.8.2 which requires "the least possible slope ..used for any ramp. The maximum slope of a ramp in new construction shall be 1:12." 
That said, most curb ramps are designed to the greatest possible slope - And constructed at the standard 6' in length. 

As we all know 1:12 (8.33%) slope, 6" high, provides a 6' long curb ramp. Curb ramps are typically constructed 6' long when they are located at a 6" high curb and gutter - in assumption this would comply (based on my recent math calculation). - Unfortunately, this is a common assumption and is not accurate when we have additional "hidden" slopes.

Let's take a retail center for example.  It has a walkway along the front of the building roughly at 2% or 1/4" per foot from the face of the building to the back of curb. Here's the problem: When a 6' curb ramp is installed, it will end up with an additional 1-1/2" increase in height due to the sloping walkway and a running slope of 10.5%.  

Indicating 1:12 max on construction documents may be technically correct (although it still is not the least possible slope), but may also require additional direction for the actual construction of curb ramps. 
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