In spite of the fancy digs they create for their clients, custom builders are not known for maintaining high-profile headquarters. Even by industry standards, though, the home of Horizon Builders could only be called modest. Located in a low, brick office park in Crofton, Md.—a below-the-radar suburb an hour's drive from Washington, D.C.—Horizon's offices offer scarcely a clue of their presence. This visitor circled the building in confusion until a kind Horizon employee appeared, revealing the door to the company's suite. To the uninitiated, the location presents not only a maze, but also a riddle. Why are the favorite custom builders of Washington's power elite, who count among their clients political leaders, national media figures, and the heaviest hitters of the local business community, hiding way out here? To those who know the principals, though, the undisclosed secure location is perfectly in character. A couple of neighbors who decided some 27 years ago to quit their jobs and start building houses, Joe Bohm and George Fritz remain regular guys, utterly without pretension. They are also among the smartest builders the editors of this magazine have ever met. Their Mr. Inside/Mr. Outside partnership—Bohm in the office and Fritz in the field—follows a model common in the custom building business, but these two run it better than anyone else we know.

A Horizon project currently under construction makes the point in a number of ways. The house is an unmistakable projection of capital-city power—in its location (a wooded bluff above the Potomac River), in its 22,000 square feet of living space, and in the seeming acres of stone and slate shingles that clad its exterior. The house's country manor style befits its owner, a former U.S. senator, and the architecture, while not groundbreaking, is indisputably first-rate. The finish work, well under way, looks great. What makes this uniquely a Horizon project, though, becomes clear only gradually. Some of the evidence is visible in details you just don't see every day: full pan flashing and hurricane clips at every window unit, caulk in the joints of double studs. But it is the way that Fritz and Horizon vice president of operations Abe Sari talk about the house that makes clear that we are beyond the belt-and-suspenders approach to building and nearing the realm of obsession.

Joe Bohm (left) and George Fritz. Photo: James Kegley Among the builders seeking this job, Sari says, “the costs were very close, so that wasn't an issue.” Horizon landed the project by going beyond the typical role of a builder from the very start. “We had built in this area before,” says Sari, who knew that the neighbors were particularly sensitive about traffic, noise, and the impact of construction on their narrow road. So the company developed a plan to answer these concerns before they arose. They would protect the road and trees with mats and temporary drainage; they would set up remote parking sites and negotiate with a local church to use their lot for overflow parking. They also suggested alterations to the site plan that would help the building sit more comfortably on the land. The house lies along the approach path of jets landing at Reagan National Airport, so the company hired an acoustical engineer to consult on soundproofing. The owners signed on, Sari says, because “they liked our process, they liked our package, they liked our interest. We had a plan.”

Best-Built And if in laying out that plan, Horizon went beyond the traditional builder's job description, that was only indicative of what was to come. Horizon isn't content to merely execute architects' plans and specifications. The company's trade contracts include what it calls “Exhibit B”—a performance standard for crucial aspects of the job, down to the sealing and vibration damping of HVAC ducts. “If you get it really right and tight, you can get it down to 2 percent, 3 percent leakage,” Fritz notes. The wall section for this house showed masonry ties, he says, but “there's no spec on ties.” How does he know how this piece is going to perform? “You get the tie manufacturer involved. You ask, ‘What does this tie do with a 2-inch embedment in a 2x6?' Then you double-, triple-check” with architects and engineers and test the ties by building a mock-up and spraying water on it for a day or two.

As often happens when Fritz discusses building technology, he is building up a head of steam. A former Maryland state trooper, he still seems to regard it as his mission to protect the innocent from harm. Now, though, the threat comes not from hoodlums but from moisture infiltration, heat loss, and uncontrolled ventilation. Pointing to an elevated stone patio with interior living space below, he spools out some data on the local climate. “We have 57 freeze-thaw cycles a year, typically,” he says. “Freeze-thaw is a big issue. When we put one of these down, we build a [temporary curb] around it, and we fill it up with water for a week or three and see what happens.” A house this size inevitably includes a substantial amount of structural steel, but Fritz hasn't been satisfied with the work of the commercial steel fabricators he has used. Now, he says, “We have our own welders on our staff. We do all our own steel fabrication on the site.” If this sounds like a quality-control focus that borders on personality disorder, you're starting to get the idea. And it doesn't subside with the client's final payment. “This house,” Fritz says, “I'm married to this thing—until they die, or their kids die, or I die.”

When you make that kind of commitment to a building, it had better perform. According to Joseph Lstiburek, a world-class authority on building science (he co-wrote the U.S. Department of Energy's Moisture Control Handbook), it will. “I'm kind of biased,” Lstiburek says. “I think they build the best houses in the United States.” A longtime consultant with the company, Lstiburek visits on a bimonthly basis to inspect Horizon projects, which he often uses as examples in his seminars. “I take lots of pictures and say, ‘This is the way people ought to do things,'” he says. “They've been building what we say they ought to, and then improving on it. These are, by any stretch of the imagination, high-performance building enclosures. The architecture is first-class, but so is the building science. I've never had the opportunity to work with buildings like that before.”