Three years ago I didn't know anything about building," said Sam Boyce as he walked through the house here that he has nearly completed himself. "The most complicated thing I had ever put up was a shelf.

"But when our old house burned down and the insurance money just paid for the mortgage, I knew the only way we could afford another house would be to build it myself."

Boyce took a three-week house-building course at an "owner-builder school" called Heartwood in Washington, Mass., which runs residential programs each summer.

At least two dozen schools similar to Heartwood have sprung up around the country in the last five years, helping to encourage the 200,000 people yearly who attempt to build their own home.

"Going to school helped immensely," Boyce said, "not just for the information I received, but especially because they revived my confidence in myself--that I could actually do it. Of course, building this place hasn't been without problems, but I've solved them, and that's made it one of the most satisfying experiences of my life."

"I built every window and door in the place rather than buy them," Boyce said,"and saved more money than even most owner-builders. I've kept a journal of time and money spent since the beginning. By the time I'm finished this summer, the whole place will have cost $25,000, including $2,000 spent on the solar hot-water system."

The house has three bedrooms, a large bathroom and laundryroom, and occupies some 1,500 square feet. By Boyce's reckoning that comes out to less than $17 per square foot, a figure that compares favorably to prices for contracted houses in the area, which range from $40 to $60 per square foot. If Boyce were to sell his house on today's market he estimates he could get $65,000 for the house alone, a profit-over-materials cost of $40,000.

"Not bad," he said, "for a little over a year's work. But I wouldn't sell--the place means too much to me now."

In the greenhouse Boyce gestured to the heat exchanger and controls for the solar hot-water system.

"I think I oversized it a bit," he said. "Yesterday was cold but sunny, and the thing shut off at noon when the water in the tank was already 170 degrees without spending a penny on fuel."

By some estimates, one out of every five houses built this year will be owner-built or owner-finished. This is largely a result of skyrocketing labor and financing costs, which have restricted the housing market to the affluent. With the average price of a new house today over $84,000 and interest rates at 18 percent, a couple would have to pay nearly $12,000 a year in interest rates alone on a 20-year mortgage, a price only 5 percent of the American public can afford to pay.

Owner-building does not necessarily mean that you pound every nail yourself however.

"About half of our students go on to build or remodel entirely on their own," said 37-year-old Elias Velonis, who with his wife Isa founded the Heartwood Owner-Builder School five years ago. "The rest simply don't have the time to do it all themselves, but they usually design it and take an active role in the construction by working alongside hired carpenters." The savings from owner-finishing or owner-contracting still can amount to 20 percent to 45 percent of a conventionally built house.

"Most people who come to us show more common sense than the building industry," Velonis said. "They are clear about wanting to build an affordable and energy-efficient house. It's not difficult to build a tight, well-insulated house, oriented to the sun rather than the street, one that's bright, personable, and easy to heat and cool, rather than the look-alike heat-leaking tract houses that are commonly built these days."

But how do banks look at owner-built housing? Is financing available to novice builders? Robert Poskind, founder of The Owner-Builder Center Inc., another house-building school in Berkeley, Calif., said that some banks express reluctance to lending to first-time builders, though the mood is definitely changing.

"More and more people are building their own and succeeding," Roskind said, "and the banks notice that. We provide the background necessary for the prospective builder to approach a lending institution confidentally, with plans, permits, and cost breakdowns ready for their inspection. Yet according to a recent survey we conducted with our past students, only 18 percent go for a conventional construction loan from a bank. The great majority of owner-builders finance their projects from savings, loans from friends and relatives, and smaller collateral loans like second mortgages."

One common financing strategy is to build small to finish a basic portion of the house for $10,000 to $20,000 and then add on to it over the years as money becomes available. John and Rebecca Morgan have built what they call their "seed home" in North Carolina, a 20-by-30 foot basic structure with kitchen, bath, living room and one bedroom.

"It cost us a little over $11,000, not including the price of the land, road, or well, which were another $5,500," John Morgan said.

"It's perfect for our needs just now," Rebecca Morgan said, "and we were able to finish it within four months." The Morgans have designed their house to easily accommodate additions on three sides, which will include more bedrooms, a family room, and a solar greenhouse.

For thousands of people like Sam Boyce and John and Rebecca Morgan the dream of owning their own home has become a reality, not through the burden of a 30-year mortgage, but through some excellent schooling and their own determination and self-reliance.

If you are interested in enrolling in one of the owner-builder courses, contact the following schools for infomation:

Cornerstones, 54 Cumberland Street, Brunswick, Me. 04011. Phone: (207) 729-0540.

Heartwood Owner-Builder School, Johnson Road, Washington, Mass. 01235. Phone: (413) 623-6677.

The Owner-Builder Center, 1824 Fourth St., Berkeley, Calif. 94710. Phone: (415) 848-5951.

Yestermorrow, Box 76A, Warren, Vt. 05674. Phone: (802) 496-5545. CAPTION: Picture, Sam Boyce and the house he is building for under $25,000 in Woodstock, N.Y.