BLACKSBURG -- The ambiance of the construction site/television set of "Extreme Makeover: Home Edition" was hangdog early Wednesday.

Volunteers paced the site with hands jammed in pockets and heads bent against the cold, but not much more was happening in this effort to demolish and rebuild a Blacksburg house in 107 hours.

Mechanical failures and unexpected problems with excavation of the foundation for Carol Crawford Smith's new house threw the tightly scheduled project, which formally began Tuesday, off by about 12 hours.

That might not mean much for a regular construction project, but it's a big chunk for a crew that has until Sunday to finish a job that would normally take six to eight months to complete.

Concrete trucks were supposed to roll in Tuesday night, but didn't start pumping until late Wednesday morning. Building Specialists, the Roanoke contractor that's organizing the project, brought in extra workers and juggled the construction schedule to make up the lost time, Vice President Jonathan Hirst said.

"We are definitely behind ... but I have no doubt this crew will finish on time," coordinating producer Diane Korman said.

All the "Extreme Makeover" projects fall behind at one time or another, but in all but one of the more than 50 shows, the crew has finished on time, Korman said.

Crews didn't wait for the concrete to set. Instead they got to work building the walls off-site. So when the concrete did dry, walls would be ready to be swung into place, said Amanda McCreary, a project manager for Building Specialists.

Richard Newcomb, president of Newcomb Electric of Roanoke, which is donating about $75,000 worth of materials and labor to the project, said Wednesday morning that communication was good on the site and he was confident the crews would get back on schedule.

"Everybody was smiling and talking ... as long as people are communicating, the job will get done," Newcomb said.

Smith was chosen from thousands of applicants to receive a new, handicapped-accessible house from the show, which travels around the country building specially designed homes for needy families.

The world-class ballet dancer contracted multiple sclerosis about five years ago and now has trouble walking. Her house was built in 1952 and has multiple steps inside and out.

By 5:30 p.m. Wednesday, most of the walls were in place and the roof trusses were being unloaded using a tall crane.

Hirst, who is overseeing construction, said he'd had about two hours of sleep in the past two days and expected to continue working through Wednesday night.

"I'm running on adrenaline, coffee and maybe a little bit of fear," Hirst said.

EMTs and firefighters haven't had much to do since the construction began. Medics have treated a few cuts and a mild case of hypothermia, EMT Kara Canaan said.

Canaan also confirmed that Ty Pennington, "Extreme Makeover's" star, had left the set to travel to Texas. Others of the cast were seen briefly Wednesday.

For most of the day, about a dozen spectators gathered behind security gates lining Ardmore Street. But crowds started to stream in after the end of the workday to see the progress.

Officials expect the south end of town to be mobbed by onlookers on Saturday and especially on Sunday, when the show's crew will unveil the house to Smith and her two sons, Hunter and Garland.

Virginia Tech will open its commuter lot on Prices Fork Road over the weekend. Parking will also be available at Kent Square on Draper Road and the former Red Lion Inn at 900 Plantation Road. Shuttles will run between the lots and the roads around Ardmore Street.

The excitement and traffic had not migrated to downtown Blacksburg on Wednesday, though another part of the show is taking place there. Virginia Tech students were installed in Bollo's coffee shop, working on end-of-term assignments and studying for tests.

Across the street, workers in the blue T-shirts distributed by "Extreme Makeover" to volunteers were carrying building materials into Smith's Draper Road dance studio, which is closed all week for renovations. Town officials have approved major work for the building, which required Smith to navigate a long stairwell to teach her students.

Even when the house is completed and Smith has settled in, interested neighbors will have to wait several weeks for a peek at the inside.

She can't show it off until the episode profiling the project airs on ABC.