Used primarily as a workshop, the decrepit 15-by-18-foot structure was crumbling from termite damage and wood rot, and the roof was leaking on Smits' tools as well as on the pale yellow 1964 Jaguar XKE he has been lovingly repairing, part by part, since the couple married 22 years ago.

"We drove away from our wedding in it," said Nelson, who has her own business as a nonprofit fundraising and board development consultant. "It's run a half dozen times that I can remember."

"I knew when I bought it that it was delicate," said the unflappable Smits, a principal mechanical engineer for BART. "It had a troubled childhood."

In deciding what to do about the garage, Smits first looked into buying a prefab "tilt-up" structure from Tuff Shed. But that company requires an 8-foot clearance on all four sides, and the Smits-Nelson garage, located on the corner of their lot, was actually sitting on the property line on two sides.

Realizing prefab wasn't an option, Smits went down to Oakland's Office of Planning and Building to find out what kind of permit he would need to build one himself.

He decided it would be best to get a permit to repair and rebuild the existing structure. If he changed the size or design in any way, he would need a full-blown design review and variances from the neighbors. So he made a plan to support the roof, dig and build a new foundation, take down the walls and build new, earthquake-safe ones, then put the old roof on the new building.

Any walls that face someone's property have to be fire-rated, so he had to move the garage's one window from the back wall to the side facing his house. And he did the electrical wiring himself.

Although he had never taken on a project of this magnitude, his wife had no doubts he could do it. "Barney knows how to do everything," she said. "And what he doesn't know how to do, he asks his dad, who is the most amazing engineer."

He started in November 2007 and thought it would take six months. It took a full year, working nights and weekends, often alone.

The only outside contractors he used were for the electric garage door, installed once construction was finished, and to lay the concrete for the floor of the garage (Smits had poured the foundation himself) and the driveway. He and Nelson laid brick pavers - which Smits salvaged from a construction site 15 years ago - in the center of the driveway, which extends from the garage to the high fence enclosing the yard. Now it doubles as a patio area when the weather's nice.

Smits did get help from friends and family. The couple's only child, Madeleine, now away at college, was a senior at Head-Royce School in Oakland last spring when her friend Hanna Paige Schurman decided to work on the garage for the month of May as her senior project. She was a theater tech person, and is now majoring in that field at Syracuse University in New York, so she knows her way around a toolbox.

"So there was Hanna, all 110 pounds of her, holding this 120-pound pneumatic nailer over her head," Smits recalled. "There is a big difference between construction 100 years ago and today. The old garage had 10 supporting 4-by-4s. Now it has about 50. And with all the Sheetrock, shear walls and redwood shingles, there were a lot of nails to put in."

Nelson's brother Larry flew out from Michigan a couple of times, and after Smits got sidelined by a hernia last summer, a lot of people jumped in to help, including reinforcements of the musical kind.

For many years, Nelson and daughter Madeleine have sung in the cast of "The Christmas Revels," a lavish holiday production staged annually in Oakland. Nelson remembers one Saturday in August when they had a crowd of "Revels" folks and Madeleine's teenage friends over hammering and hoisting while singing old English pub songs and medieval and Elizabethan tunes from past "Revels" shows.

"People would walk by and hear the singing and peek over our fence to find it coming from this construction site," Nelson recalls. "Afterward we all ate a big feast. It was like an old-fashioned barn raising."

All told, 17 people besides Smits worked on the project, which technically concluded in November, when the building inspector signed off on it. This month the couple painted the side walls pale gray, offset by shiny new toolboxes, and the back wall British racing green. Smits said he plans to have a celebration when the weather warms up.

"I'll have everyone over for a beer," he said in his typically low-key manner. "We're not going to break a Champagne bottle on it. We put too much work into the shingles."

Don't miss our Home & Garden section on Sunday.

Regan McMahon is an Oakland writer. E-mail comments to home@sfchronicle.com.

This article appeared on page E - 1 of the San Francisco Chronicle