I’ve boarded at two barns that were converted. The first place had very low ceilings. I had a colt and then a (different) gelding throw their heads in the cross ties and destroy the light fixture (it was in a plastic case, like an office would have). I know my horses weren’t the only ones to take out the light.
The other issue was the cement floor, after many decades, was worn completely smooth. It wasn’t a problem until it was (i.e. a horse slipped and went down). The nice thing about that place was at least the stalls were dirt floor, so they were dug down and the horses had better head room in the stalls than in the isle.
The second barn is adorable. They don’t have nearly as low of ceilings. However the stalls and the isle has concrete floors (we just mat them and bed like normal). The walls are block (almost look like huge bricks) and we had a horse kick many holes into his stall–worried about it, he was ultimately moved to a wood-walled stall. They filled in the drainage areas, etc. w/concrete.
I will say, both store hay above in the loft (second in the barn as well). In addition to the fire hazard, it is the dustiest arrangement. Dust comes down through the floor boards overhead and just coats everything.