"Ramps" are typically location-specific. Yours needs to go from what point to what point? Ramp design requires dimensions and elevations to even begin considering. Also weight and dimensions of the loaded chair.

"Portable ramp"? Again, depends on from-where/to-where? Are you talking about known locations?

The characteristics of whatever your particular situation may be make evaluation from cyber-distance pretty difficult. And doing it wrong can be VERY hazardous.

According to a chart on ebay I would need a 14 foot ramp and they don't make the portable ones that size. I need a ramp to get my mother off a porch on my house. She can't do the steps (we tried it today). She can go from the porch to the car which I park very close to the steps but she can't go up and down the steps with just me assisting and I don't always have help. She is approx 120 lbs and the chair probably 30 lbs.

Best is to call a good handyman and get an estimate.

Ramp directly over stairs would typically have too great a slope for safety.

From what you've written, I'm not sure you're entirely getting the concept of what may be required. In any event, from what you've written, I can't come close to discerning what may be needed.

Suggest having this eye-balled and estimated in-person on-site by a competent person. I doubt you're going to learn what you need here.

No the ramp would not be over the steps but at another place on the side of the porch. Yes, I will have someone come give an estimate. Thanks for your comments.

Please check with your building dept. Where we use to live, they required permits and will check to see if it meets ADA requirments. Built wrong can be very dangerous.

No permit required where I live. I trust the man who is coming to give me an estimate. He's not a fly by night but someone who has done work for me and my family before. I'm sure he is competent to build a wheel chair ramp.

I will second and third the warnings about building ramps. If the angle is too steep, it can be horribly dangerous. And, of course if the materials are not sturdy enough, that's another problem altogether.

I once looked at a licensed assisted living private care home in my area. They had an opening, so I went to check it out. It turned out to be a room in a converted garage. The garage originally was a few steps down from the house, so they built a ramp. In order to save space, it was built at such a steep angle that I knew my mother could not navigate it with her walker. When I expressed my concern, the owner said they'd always make sure a staff worker helped my mother getting too and from her room. I thought to myself, "Oh, great! My mom will always be at the mercy of a staff worker to get in & out of her own bedroom." Needless to say, I didn't even consider that place.

Wheelchair ramps have to be built to code which is 12:1 for safety. That means for every inch of height it should be one foot of ramp. A 3 ft high porch would take a 36 ft ramp. After a ramp is a certain length you also have to install a "landing" I believe, and also handrails , or if it isn't extremely high a "toe rail" of sorts so keep the chair from rolling off the side. If a long ramp is needed a porch lift is the better purchase, plus it doesn't have to be cleaned off in bad weather, weather proofed, etc. like a wooden ramp does.

Wheelchair ramps need to be 12:1 that's 12 inches run for every foot of rise. Depending on your state there are places that can assist if you qualify and most do because of disability or elderly. Check your state DSS site on the internet and see what they offer. My state will provide a free ramp on HCBS funding, the ramps are measured, ordered and then built in prison work programs and then delivered and installed. You could also see if there is a community agency like "Neighbor Works" who assist with funds for the low income/disabled through "Block Grants" your town may also have a community development program that you can apply for funds for accessibility. Also try your State Home Builders Association, they have a helping hand program so contractors can do community projects, it is little known that these contractors get a tax deduction if they give a low rate or free work to the disabled or low income.