"When they start to overdo it, when they start putting in the double lifts and customizing the garage, that could hurt the marketability of their house on the next sale, " he says.

WSJ: Luxury Garages: Where the Car Is King��WSJ Mansion

There are 44 lifts, some of which are double-decker, which have no buttons on the inside.

BBC: Does Shard point to design's future?