Dimensional Tolerances in Construction and for Surface Accessibility

Department of Justice method
In the tips and techniques section of "Survey Tools and Techniques," (www.usdoj.gov/crt/ada/ckstools.htm) the checklist states that slopes can be measured in three ways: with a land survey to shoot grades, using a digital level, or using a 24 - inch long builders level and tape measure.

The directions for using a level are as follows. "Using a builders level, place the level on the pavement at the steepest point parallel to the direction of the slope. While holding the uphill end of the level on the pavement, place a pencil under the other end and roll it toward the uphill end of the level until the horizontal air bubble shows level. Use the tape measure and measure the open gap at the downhill end of the level to establish the critical dimension. For a 1:50 slope this is 1/2 inch; for a 1:20 slope it is approximately 1 - 1/4 inch and for a 1:12 slope it is 2 inches."