Like many old homes, the back stairs in the 1800s farmhouse in The Plains, Va., being renovated by architect Anthony Barnes, Barnes Vanze Architects, Washington, D.C., had small winders, which, while efficient, were neither safe to use nor up to code.

“We needed a practical, elegant way down to the first-floor family area from the children's bedrooms. On the main floor, the vista through the house to the fields couldn't be disturbed by the new stairs. Only a small space was available; efficiency was everything.”

Codes require that within 12 inches of the narrowest part of any tread, there must be 9 inches of useful tread depth. Barnes and senior associate Tim Clites envisioned a safe and efficient circular stair “squeezed” into a rectangular box. “By angling the noses of the treads even while you're on a straight run and not on a landing or corner,” Barnes says, “you can have a deep inside dimension on the tread so it remains safe for the whole journey.”

The stairs were built in one piece by Harmonson Stairs, Mount Laurel, N.J., and delivered to the site and installed by Walnutdale Building Co. of The Plains. Though more expensive to build than a regular switchback stair, they're beautiful and “they meet all the requirements,” Barnes says, “so the owner felt it was well worth it.”