I'm not citing any specific code, although minimum 8ft ceilings comes to mind, but I'm sure that a building can't be the size of the other buildings around it like the crypts and such and still be functional as a retail shop. Now could they have scaled it better to fit next to the mansion and still be within code, maybe. But I doubt they would just build it larger than needed just to purposely ruin sightlines and scales. So any structure size was likely more related to its function rather than just because someone didn't care.