Question
Two Story house w/ basement apt. Yard is sloped with more that 14% grade to street. We need to add a sidewal for accessibility for aging parent who uses a motorized wheelchair. How do you determine the length the sidewalk must be? It can not go straight from the door to the street becasue it would be too steep. What are some resources to use to come up with the design?

Answer
Donna:

For a personal residence there is flexibility to do what ever is best for your personal needs. However, for public ramps we follow these requirements:
The ramp can be as flat as you like but the ramp should not exceed 1/12(8.33%) or one inch of fall for ever 12 inches of length (1 foot) and should have a safe flat landing every 30 feet for resting.  

You will need to have the elevation of the parking area and subtract the elevation of your basement to come up with the total amount of fall.

For example say your parking area is at 5000 feet (above mean sea level) and the basement's finished floor is at 4980 then you have 20 feet of fall (5000-4980).
Now divide 20 by 8.33% (20 / 0.0833) equals 240 linear feet.

Check this by a second equation 20 feet = 240 inches (20X12). for every inch you need a foot of ramp. So it checks out(240=240).

Now divide 240'/30' (you need a landing ever 30 feet) = 8 so add 8x5'=40'
you need 8 five foot landings or 40 additional feet in length. So the total ramp and landings would be 240'+40' or 280' feet long.

This would require switch backs with a landing or flat area at each location that the ramp turns.  Rails are recommended on both sides.

See these links for more help:

http://www.access-board.gov/adaag/html/adaag.htm
http://www.access-board.gov/adaag/html/adaag.htm#4.8
http://www.mobility-advisor.com/wheelchair-ramp-specs.html
http://www.rampsplus.com/ada-ramp.asp

Also, check with the company who manufactures the scooter and be sure that you design a ramp to be in the tolerance range of the preferred slopes for every day use. A scooter may be able to handle a 8% slope occasionally but for every day use, it may not be the best.


For the best results I recommend you hire a registered landscape architect to prepare a design for you if you want to be sure it is safe. Check the www.asla.org site for listings of LA's in your area.

Other than searching "handicap ramp design" or "ADA ramps" on the Internet I am not familiar with any specific books or design tools. Each ramp is tailored specifically to meet the needs of the specific site.

Best of Luck
Sean J Murphy
www.amenityarchitects.com
www.seengineering.com

Southeastern Engineering, Inc.
Amenity Architects, LLC.