If you need to build a handicap accessible ramp to attach to your deck be aware that there are very specific rules that must be followed.  First you must build the ramp at a 1:12 slope, which means that you can only drop 1’ for every 12’ of distance the ramp covers.  ADA ramps that extend beyond 30’ must have an intermediate landing.  The ramp and platforms must be finished with a slip resistant surface. 

Ramps are usually framed with 2x12 stringers the same as stairs.  Because ramps will usually terminate at the ground it may be necessary to bury a part of the frame to provide a smooth landing area.  In order to do this you need to use .60  RET pressure treated lumber that is rated for ground contact.  You may also want to surround the base of the ramp with compact gravel to promote drainage.  Rails are required as in the case of stairs.  Always verify your plans with your local building inspections department before building a ramp.