Hello all,
We have a free-standing/detached 14x20 stick-frame garage on a what seems to be 4" slab. We were hoping to convert it to a creamery to make cheese and dairy products on our small farm, but would need to add-on to have enough space. Trying to figure out if and how that should be done...OR if we should just try and build something new. We live in northern New York (something like 42" to 48" frost depth I think).

The garage we guess is at most 12-14 years old. The slab looks good, no cracks - yet. No idea how well reinforced or not it is. So the slab may be "strike one" against retrofitting the building. Plus, the walls go right to the floor, no concrete curbing or sill. We'd want to jack up the building and add a couple row of blocks, I think (strike two?). If we had to somehow add footings...well that seems like its pushing us in the build-from-scratch direction.

If adding onto a slab-on-grade structure, should the new one have proper frost-wall/footings? Or slab as well? But either way, is it likely that either the original or the addition will shift and pull away from each other? Not really sure about all the considerations that should go into this kind of construction.

Or is the simplest, most structurally sound thing to do just to build from scratch?

Thanks for the advice!