I have never heard of that or seen it. I can see numerous issues with it:
(1) the required length of the ramp. A wheelchair ramp is supposed to have a 12:1 pitch, 12' of ramp for every foot in change in elevation. You will have about a 8' change in elevation. Do the math. Even if you go steeper than a 12:1 pitch, the ramp is going to take up a huge amount of space and will likely require a switchback.
(2) There must be something that blocks fire from going from the garage to the house. You would need a fireproof door at the bottom or top of the ramp. This one isn't a big deal.
(3) Expensive! You will lost a lot of square footage in the garage and/or basement and it will require a lot more concrete for the ramp and wall going down from the garage.

Seems like it would be easier to store the lawnmover in the garage, even if that means making the garage bigger.

We have a wheel chair ramp into our main level and a stairway down to our lower level. No way would a ramp make it all the way down to the lower level. The stairs are steep enough.

Now wait: On the face of it, it seems a little silly.

But it sounds like this isn't finished space... is there another access to it, or does this ramp replace the stairs?

Because if it does replace interior stairs and the basement is storage/mechanical space, a ramp would only take a bit more room than stairs, save the interior stair footage, and make access considerably easier for many things.

A lot would depend on the height difference between the garage and basement floors...

It's also entirely possible that your architect finds the idea cool, and is anxious for you to be his guinea pig-- maybe he wants to do a woodshop or somesuch in his own basement, wants a ramp for ease of access with lumber and the like, and is trying it out on your house first.

A usable ramp will take at least 6 times as much space as steps. We ran into this when mum became wheelchair bound. Between garage and kitchen there were four steps (extending about 4 feet from the door which was about 40" above garage floor) which required a ramp 28 feet long... and that felt steep when pushing a wheelchair up!

oruborus, take a strip of paper and zigzag-fold it so that it represents risers and steps. Put one end at the upper doorway, and then gently un-fold, so that the risers and steps straighten out into a flattish ramp. You will find yourself adding more and more paper to make the ramp's incline gradual enough to be usable. Think about it: most steps are about 11" deep, with a rise of 8 to 9 inches. Four steps of 11" each will take floor space of about 44". But that rise has to be ramped to be navigable and will have to extend [across floor space] until there is a 1 in 6 (2/12) slope. Believe me, you do not want anything steeper whether for a wheelchair or a mower.

If one wants a ramp -and that does sound handy for moving equipment- then check with the experts as to what is usable. I suspect the space required would be best provided with an exterior access to the basement, with a gentle slope and one or two landings for switchbacks. If one is going be pushing deadweight such as a non-self-propelled mower, a 3/12 incline is going to be more useable even though it will require more floorspace.

Do you have a sloped or walkout lot? I've seen this done where they had a small garage door in the basement that led out to the yard, but this was a walkout lot. If your lot is flat, I bet you could build a bigger garage or a separate shed in the back yard for less money that takes less space.

Our lot will barely miss the requirements to be a walkout. I am sad about that. Our house now is a walkout and we do have a utility garage door for the mower. I agree with all of you so I am forwarding all of this to my husband and I think he is starting to back off the idea. I was figuring that it would have been shot down eventually by the draftsman, builder or cost anyway! We'll see!!!

Do you want anything with GAS in your basement???? Anything that is used outside and with gas would have to stay in a shed at my place.....I'd be so afraid of combustable materials catching fire, not even sure if you could do this legally. I'd encourage your DH to build a shed area "All for himself" beside or into the existing garage.
GL

Good point! Big box stores here won't even accept returned gas powered equipment unless you drain the tank first.