This staircase is the first thing you see once in the door. The maple, walnut and mahogany newel is beautiful, as is the railing, which winds its way up three flights. Not so good: the two inches each tread pitches from left to right. Sloping stairs is a common problem in old row houses and there's a trade sprung up to fix them. But like so many jobs performed by skilled workers, the fix ain't cheap: anywhere from $5,000 to $10,000 a flight.