Just built a ramp for Ray, ADA compliant per the structural engineer's design. It's one foot of length per one inch of lift.

Try calling your local Center for Independent Living.  Most cities have one.  This is a nonprofit that is focused on helping people with all sorts of disabilities live independently.  They might have someone on staff who is a ramp expert and can give you some good advice.  

You could get an ADA audit performed, if you want to see what else might need work.  3rd party auditor can perform it.  There are also guidelines that you can review as well online.

Good luck with the project Fred, your local bldg dept will have the specs

Contact Steve Hoffacker, he teaches classes for the NAHB on aging in place and being ADA compliant. He can assist you! 

Fred, you may want to check with Richard Acree, ADAC, CAPS, CMA.  Over the years, I have read AR posts he has written about ADA compliance.  Good luck.  

I am betting Debb Janes EcoBroker and Bernie Stea JD may have something to say. 

My suggestion is to check the city codes for requirements. 

As we grow older, it is made apparent what makes life easier or less and for us to act accordingly...

Fred,

Each state seems to have its own specifications.  In Florida, we are involved in marketing a project for aging in place.  It is a condo project with universal design that takes into account height of appliance for wheelchairs, door handles, etc.  It has balconies that are accessible also.  I would rely on someone specific to your new state that has experience in this.  A

Check with the city and county engineer in which the project will be built Fred.

I couldn't possible add any more than what Debe Maxwell said. Learned a lot in her answer. A deck & a ramp are not always a deck & a ramp.

Ouch,  stand by for more changes to the way we do business.

Here, we would need a permit to build a deck or handicap ramp. Your local building permit office should have required specs on hand. If not, 20" of rise = 20' long ramp is standard. https://www.rehabmart.com/post/wheelchair-ramps-and-ada-guidelines-everything-you-need-to-know

You can search on houzz.com to get several ideas for designing ramps. I would guess you'll need a permit, build to ada specs, and get inspection by you local building office. It doesn't really matter who lives in the house. It might also be a good idea to consult with your local fire dept. Picture someone in back yard needing emergency help, yard is fenced, and paramedics have to put patient on stretcher and wheel him/her up ramp and through house to ambulance parked out front.

This site appears to be all-inclusive for contractors Fred:

https://www.ada.directory/

So, so many articles express ADA compliance but there are practical guidelines that take the idea to a higher level which express some more practical considerations for your specific needs. Doing more than what would be considered as required may be superseded by what could become necessary or more desirable in the future. Best of luck!

Fred, call your local building inspector

1 inch of lift per one foot of length.  I had to know this from my office handicap parking spot (that had to be asphalt or concrete to my deck at the office.  I had to put a platform and turn to accomodate the requirement.

I have no idea Fred but really interesting question.  Our contractors know and figure out all this kind of stuff as it's their expertise.   I also might add in my area 'aging in place' homes and patios typically do not have steps - and if they do not many steps and perhaps a ramp if need be.