MANY JOBS can be met with at least a mild amount of enthusiasm when building your own home.

Bad cop is not one of them.

It is, however, a vital part of the operation, and somebody's got to do it.

"That was me," says Sandra Cardozo Ainslie.

"Neill wanted a fingerprint scanner to open the front door. I had to say, 'No, we can't afford that. That's $2,500 we should put somewhere else.' "

And that is how it went, Neill Ainslie, who builds homes professionally with his sister as half of Ainslie-Davis Construction, pushing the envelope, experimenting on his own place. His wife, Sandra, right there, just a reality check away.

It was a smart combination. Because, in the end, when all was poured and plastered, pounded and painted, his exuberance and her reserve created a 2,200-square-foot contemporary home of white, open spaces tucked back onto a steep Madison Valley lot.

Neill's done this kind of thing for himself before. Built a mustard-yellow box a few blocks away, using a commercial automatic slider as his front door. He lived there for a few years, then yearned to do it all over again.

"I'm so influenced by all the architects and clients I've built homes for. I love to take those things and experiment on my house," he says, a kid with his own candy store.

This home is deceptively simple, glass walls 20 feet tall, oak cabinets (the grain running horizontally) stained ebony for richness and warmth. Heated concrete floors, the living room two steps down from the kitchen, the kitchen a true command post; the double-cantilevered white Pental Chroma quartz island as big as a dining-room table. The dining room, meanwhile, tucked into a nook surrounded by built-in wine storage and work desk. Upstairs are three bedrooms (the master cantilevered high over the yard) and two baths. All are just off an ipe walkway beneath a lengthy set of skylights.

Neill found the lot in 2008 on a jog through the neighborhood. The for-sale sign included a rendering of a modern house. Neill stopped jogging. Turns out the lot came with much more than a tangle of blackberry vines. It had plans and permits (by architect Luke Wendler, now of San Francisco).

"I called the architect and I said, 'Luke! I'm going to build this house, and I'm going to tweak it a little bit, put my spin on it,' " Neill recalls. "He said, 'That's great! It was my college thesis. I'm so excited to see that it's going to be built.' " Wendler then worked with the couple to customize the home for them.

They moved in during the summer of 2009.

Even on a budget they found ways to include plenty of special touches: the granite bathroom sink cut in a gentle slope; back-painted glass walls in the bathrooms; the massive Venetian plaster wall in the living room; stainless-steel kitchen counter and backsplash with an orbital finish; a fir sliding wall hiding the pantry; Milgard metal windows installed backward, using the flushing as trim; the MDF office floor treated with a Swedish finish.

"I call it a collaboration of me, my wife and our budget," says Neill. "We had our friend (architect) Eric Cobb over for dinner one night, and he told me that what he loved about the house is that we didn't go over the top."

The itch to build has been scratched. "We say to ourselves, hey, we're happy here. Let's just stay," he says. Sandra gives an I-knew-it nod.

Suddenly, being the bad cop's not so bad.

Rebecca Teagarden writes abour architecture and design for Pacific Northwest magazine. Benjamin Benschneider is a magazine staff photographer.