Ill-conceived

It was an ill-conceived idea. I don't know why you thought you could pull it off.

Elegant brick and stone buildings, with iron and glass canopies and decorative wooden scalloping and fencing—all evidencing care on the part of the architect to produce a pleasing, well-planned building—were submerged beneath a profusion of ill-conceived additions and camouflaged by vulgar paint schemes; and the original conception was lost.