The sign on the edge of the construction site where hard-hatted workers are erecting frames over newly poured foundations bears the slightly breathless message familiar at many new subdivisions across Northern Virginia:

"Coming in early 2005. Homes Available. Call Now."

Except that this subdivision is not going up on farm acreage or near a Metro stop, but smack in the middle of Fort Belvoir, a sprawling military installation where motorists have to show their car registration and submit to a trunk search before entering.

The new single-family homes -- boasting walk-in closets, Corian countertops, two-car garages and double-sink vanities in the master bedroom suite -- are a far stretch from standard military housing. And they are being built by a private company with a 50-year lease for the land.

By 2011, Fort Belvoir will have 1,630 new houses for military families to replace existing houses that will be demolished in phases. In addition, 170 historic Colonial brick houses -- with slate roofs, heavy oak doors and small rear bedrooms originally built for a maid -- will be renovated for the families of senior officers.

The construction at Fort Belvoir is part of a transformation in military housing underway at bases across the country.

The need for new housing is unquestioned. Col. Thomas W. Williams, Fort Belvoir's commander and landlord-in-chief, pulled out a brochure that was produced for Congress several years ago. The cover featured three photographs dated 1950, 2000 and 2050. Each shows a soldier carrying progressively more sophisticated weapons. But in every photo, the soldier is standing in front of the same, dilapidated Quonset hut.

"We have transformed our soldiers into the best fighting force in the world," Williams said. "But the infrastructure has stayed the same. If we want soldiers to reenlist, we have got to get them better housing than we had in 1950."

While the existing housing at Fort Belvoir is several steps up from Quonset huts, even the best is inadequate.

At the top of the line are the stately two-story, four-bedroom brick homes near the Officers Club. The names painted on the doorsteps identify the residents as colonels and generals. The location, on the rim of a thickly wooded ravine that leads down to the Potomac River, is spectacular. Officers hoping to move their families into these houses face a wait of up to two years.

"It's like living on a nature preserve," said Cheryl Sinn, whose husband is a lieutenant general. "It's a privilege to live here. It's the best-kept secret in the Army."

But for all the charm of hardwood floors, a wood-burning fireplace and deer emerging from the woods to graze on her lawn, Sinn said the circa-1935 house is a fixer-upper. The windows are painted shut. The one-car garage cannot accommodate anything much wider than a compact. At least one of the cramped bathrooms still has the original fixtures.

The housing reserved for enlisted personnel has more basic problems. The apartments, built in the late 1940s and early 1950s, turn over so fast that there is no waiting list.

"I don't like it much," said Lenimar Rodriguez, the wife of a staff sergeant, as she sat on the stoop of the three-bedroom, two-bath apartment her family of four moved into less than a year ago.

"When it's humid, the kitchen when it rains smells like a rat. The bathroom has mold. I clean it with Clorox, and it grows back. My daughter has a skin rash. And the stove, when I turn it on, sometimes it works, sometimes it doesn't."

In another cluster of apartments, residents say they had to sign forms acknowledging the existence of lead paint and asbestos, which has been encapsulated but worries them nonetheless. Cockroaches are not uncommon.

"I'd definitely like to move," said Tamara Cole, whose husband is a specialist. "I can't put a nail into the wall to hang pictures. And what if my kid scratches the paint?"

Across the street, Staff Sgt. Matthew Quick and his wife, Jennifer, moved out of their two-bedroom house last week. The 1,530-square-foot townhouse had only one bathroom for the family of four. Their two sons slept in a bunk bed in a room the size of a walk-in closet. They could never install a second telephone line for the Internet because it would have required running a line through all the houses in their row. The Quicks plan to buy their own house when they move to his new assignment in Georgia.

The housing situation is equally dire at many other bases across the country. Williams said a study concluded that going through the normal procedure of getting congressional appropriations for new housing would take almost 130 years. So the military decided to privatize its housing.

Originally, military commanders wanted to add 1,000 units. But Fairfax County officials expressed concern about the strain on surrounding roads.

Although the post's 5,600 residents must work for the military, most are not actually stationed at Fort Belvoir, but instead join the clogged traffic flow commuting to jobs at such places as the Pentagon.

The county wanted the military to help pay for new roads. But Fort Belvoir, which is the largest employer in Fairfax County, balked and decided to scale back its plans, building only replacement homes over the footprints of demolished housing.

The military still contemplates adding housing down the road. And the county still wants the military to pay for roads.

"We need a funding partner to realize mutually beneficial transit and roadway improvements," said county Supervisor T. Dana Kauffman (D-Lee), who acts as a liaison to the post.

Under a partnership with the military, Clark Pinnacle Residential Communities has taken over management of the existing housing and is constructing the first cluster of homes for enlisted personnel, called Herryford Village. They have set up shop in a warehouse where model facades display the vinyl, brick and shutters to be used on the Colonial-style homes.

Chris Guidi, the project director, said the homes were designed with military needs in mind. To facilitate frequent moves, staircases were built wider and straight. Every room has a ceiling light for those first nights when the lamps have not been unpacked.

Using the principles of New Urbanism, garages are reachable by rear alleys, making sidewalks pedestrian-friendly and fostering encounters among neighbors. The homes will be wired with fiber-optic cable, and videoconferencing facilities will allow spouses to communicate with military members when they are deployed.

Aesthetically, the two-story houses are indistinguishable from houses off post that are selling for $450,000 to $500,000. The smallest, for enlisted personnel, have three bedrooms, two upstairs baths, a downstairs powder room and a great room. The largest, set aside for colonels and generals, are center-hall Colonials. Spread over 2,400 square feet, they have four bedrooms, arched windows, a two-story foyer, a formal dining room, a family room and den, a kitchen island and a sitting room off the master bedroom.

Tenants will pay the company "rent" in the form of their housing allowance, which ranges from $1,303 for a private to $2,372 for a general.

Guidi said he has held meetings with most of the 27 generals who live on the post, and listened to their suggestions for improvements to the kitchens, baths and garages.

Asked what it was like working with so many generals, Guidi said, "They've all been terrific," adding with a laugh, "Some have been more proactive, sharing ideas of things that we could do better."

Private builders are erecting 1,630 housing units at Fort Belvoir, to replace aging homes for military personnel.Traditional on-post housing has frustrated Allison Thibeau, who has coped with cockroaches and mold.