What will cost $250,000, contain three greenhouses, 2,768 outdoor plants, a sauna for six, and take just 72 hours to build?

If the Northern Virginia Builders Association has its way, the creation will be a contemporary styled, four-bedroom house in Reston.

In a project designed to raise money for charity, scores of workers from construction companies in the area converged early yesterday morning on the one-third-acre site on Bennington Woods Road to break ground for the house.

It was 6:30 a.m. when the workers turned the first shovel of dirt and, if they meet their deadline, it will be 7 a.m. Saturday when the house, complete to towels in its 3 1/2 bathrooms and a personal computer in its computer room, should be finished.

"I have never seen anything like it before," said Jo Norton of Sterling as she settled down in a lawn chair to watch the two-story house rise. "It looks like quality work . . . . As long as the house stands up, who cares how it's put together."

Ray F. Smith Jr., chairman of the building project, said the house will take the efforts of more than 2,000 individuals and 60 pieces of construction equipment.

Normally Smith said it would take "at least nine months" for construction crews to finish such a house. It contains 5,100 square feet of space, has a two-car garage, an exercise room, a whirlpool bath that will seat six, two fireplaces and a 20-foot vaulted ceiling.

The builders, who are donating workers and materials for the project, are selling $10 raffle tickets at paint stores and other locations in Northern Virginia through Nov. 15. They will give the house away in a drawing on Nov. 22.

Electrician Charlie Donoghue was resting on a pile of lumber away from the din and dust when he said he is splitting the cost of a raffle ticket with four other workers.

"If we win, we figured we'd sell the house . We could never afford the upkeep of it," he said.

Gusta Farrar, who dropped by and joined the crowd of nearly 100, watching the crews on her lunch hour, said she planned to buy several tickets.

"I'm very impressed with this and would like to have this crew at my home," she said. "I would think a house with this amount of attention would be well built."

Reston resident Joe Harrington, whose back yard adjoins the house, said the notion of 72 hours of nonstop noise disturbed his wife and she considered moving to a hotel until the house is finished.

"But I think it's exciting," he said. "Besides, we have the air conditioning on so maybe it won't be so bad."

After Saturday, the house will be open to the public from 10 a.m. to 6 p.m. daily until Nov. 15.