Playtime hits the big time

For Barbara Butler, playhouses are serious business.

Drawing on her own childhood growing up with seven brothers and sisters, the San Francisco-based designer and builder creates whimsical confections worthy of the most active imagination: trapdoors, jail bars (''One of our most popular options,'' Butler says. ''Kids are really into the jail theme''), swinging ropes, peepholes, escape hatches, fireman's poles.

All that creativity doesn't come cheap, but Hollywood, design magazines and a growing number of people across the country have added their names to a waiting list of clients eager to play.

''It's not just a kids' zone anymore,'' says Butler, whose work was featured in the Robin Williams movie ''Bicentennial Man.'' ''It's where the future is -- so the whole family can have fun together.''

On one playhouse, each arched door has a sliding peek window that Butler calls a ''who goes there.''

Climbing over and through the structure offers a maze of possibilities. ''There are easy ways up and hard ways up,'' says Butler, ''but quick ways down.''

One of the hard ways up is a side wall pocked with stones molded with handholds and toeholds. ''We order the stones from a rock-climbing magazine. They can be positioned with the indentations up for easy gripping or down to raise the difficulty.'' To get back to the ground, choose the blue tube slide or the stainless-steel fireman's pole. A walkway above the swings leads to a second tower, a four-foot-square fort with a brass-knockered door and a rope net attached to a parapet above. There's a working flagpole with three flags, including a "white flag of surrender, just in case.''

Butler says her designs draw on childhood memories of growing up in a big family in Upstate New York. ''We had a terrific rope swing in an old tree. And two metal bars at different heights, like chin-up bars. There was a three-foot-high rock wall around part of the house that we would pretend was a ledge next to a lava pit when we were learning to climb.''

She started out studying political science in college, but after graduation learned bricklaying and construction from an older brother, James, a contractor. After an intermission in graduate school, she moved to San Francisco in 1983 and started a company called Outer Space Designs with a friend. ''We specialized in decks, hot tubs and fences but did not even think of play structures.''

Singer-songwriter Bobby McFerrin hired the duo to build an elaborate deck, and his wife, Debbie, asked for a playhouse. ''Once I had done one, another couple saw it and became interested, and it just started snowballing from there.''

Her company, Barbara Butler Artist-Builder Inc., is co-owned with her sister, Suzanne Butler, and husband, Jeff Beal. The firm has grown to 13 employees and usually has about eight projects going at once. Her work was included in ''The Treehouse Book'' by Peter and Judy Nelson with David Larkin published in June (Universe, 224 pp., $25). She displays her designs at garden shows across the country, and on her Web site, www.barbarabutler.com.

Butler's play structures range from portable models starting at $2,400 to custom fantasy spaces in the $16,000-plus range. While Butler agrees that's a lot to spend on a playhouse, she points out that it's often less than building a family-room addition. Plus, ''it gets people into an outdoor room, in their yard, to be active together.''