Next I created what I refer to as the slope evaluation process. The slope evaluation process is a method to determine the slope of any ramp project. The fundamentals are to calculate the slope using the ADA 12:1 slope ratio – for every 12 inches of horizontal travel, the ramp can only incline or decline no more than one inch of vertical travel. For example, if there is a 15-inch elevation change, a 15-foot ramp is required.

Although we are calculating the ramp, we ultimately must plan on the entry/exit edge of the concrete pad. I begin by determining the elevation change of the door threshold and the approximate location of the future landing pad. Measuring down from the threshold is known as measurement “A,” which is measured in inches. Assuming the grade is level for simplicity’s sake, we plug measurement “A” into our process and we figure out measurement “B,” which is the length of the ramp. Measurement “B” is in feet. Now we have two legs of the slope evaluation triangle; the third leg is the line connecting “A” and “B.” This line is “C” and designates the actual walking surface of the ramp.

I draw this slope evaluation triangle on utility paper and one can simply attach this triangle to the building wall as a guide. If obstructions prevent the triangle from being taped to the house with line “B” being level, then turn the triangle upside and backwards and tape it to the wall. As long as I start at the door threshold and line “B” is level, then I will be able to determine where the lower level concrete landing should be located.

This process works for every ramp. Please see Illustration A-5 to see the slope evaluation triangle specific to this particular project.

Illustration A-5

In this particular case, the mid-run level platform was merely an interrupt of the slope; this did not change the slope triangle. It just interrupted it (see Illustration A-7.2 below). We had to determine the approximate elevation change to determine where the concrete pad was going to go. In this case, the concrete pad would be around the corner and I knew I would be creating a 48”x48” pad that would be level with the Earth. The pad location ended up being something of a moving target. Usually, the elevation changes from below the threshold and where the pad is going to go. If the elevation goes up, one would have a shorter run and the opposite is true as well.