Adaptive reuse of parking structures

This post here asked an interesting question about a proposed parking structure:

“How smart a use of land and resources will those 2300 parking stalls seem in 20 years?”

My immediate response was that is depends on whether the garage is designed for easy adaptation to another use. Sure the parking stalls might (arguably) not be needed but a sturdy structure will still exist.  I expected the issue to be a cakewalk.

So I started thinking about it and wondered what "easy adaptation" actually means for a parking structure? What are the factors? I don't know for sure of course and this is really a question for architects and structural engineers. To the layperson most parking garages seem quite stoutly-built, very often of concrete, so it would seem plausible that they should be able to handle a wide range of uses. In addition, the (typical) concrete floors should provide those critically-important "fire separations" required between different uses.

And some other factors came to mind:

1. "Adequate" headroom for a range of typical uses.
2. Minimum ramps and maximum level floor plates as you don't want to have to contend with a Guggenheim Museum ramp.
3. "Adequate" floor loads as believe it or not cars are not that heavy.

Factor one — decent headroom — might be an issue as most garages are built with something like minimum head-room of  7 feet to the bottom of a beam and then maybe up to 8.5 feet to the bottom of the floor above. No one expects them to be anything but a parking garage. Concern for economy also suggests minimum height. So not good for adaptive reuse. But hey! what about storage? You don't need (or  want) high ceilings for mini-storage. Let's see.

How about factor two, level floor plates? Unfortunately a lot of the nicest (for a driver) parking garages are a series of ramps with very little level area and that often at the hairpin turns. Maybe not too promising even for storage.

Well surely we are OK with factor three — strong floors? Alas, it seems not. I just did a quick check and through the magic of Google came up with another piece of bad news: Passenger Vehicle Parking Garage Live Loads. It appears that parking garages can be designed to the same or lower "live load" than apartments or single-family houses: 40 - 50 ponds per square foot. Isn't that amazing? But it make some sense. A car weighs (say) 3000 pounds and takes up a space of (minimum) 9' by 18' or 162 square feet (sf). Simple math gives you 3000 pounds over 162 sf or 18.5 pounds per square foot! Pretty amazing, huh? There are 4 point loads per car where the wheels touch the parking deck and the code does make some special provision for them.

Bottom line: it looks bad and that adaptive reuse of parking structures as they are built today may have issues so substantial as to make it impractical. The typical contemporary parking garage is not in fact a "warehouse for cars" which can be converted easily to glamorous lofts for young moderns.

Of course, again, I am no architect or engineer so I may have gotten this analysis all wrong and will be happy to be corrected.