RICHMOND -- Builders are constructing homes on smaller lots and they're putting up fewer houses on speculation as home sales dropped 11 percent in Virginia last year.

December sales were the lowest monthly total of the year, the Virginia Association of Realtors reported this week.

In its monthly report on housing sale contracts, the association said 63,974 contracts were recorded in two dozen metropolitan areas in Virginia in 1990, down from 71,870 in 1989. In December alone, 2,920 contracts were recorded, down 14 percent from 3,414 in December 1989.

In a separate report, Virginia home builders said they generally were building on smaller sites than a year ago and were building fewer speculative houses than a year ago.

The Virginia Real Estate Research Center at Virginia Commonwealth University surveyed 500 home builders around the state in November and received responses from about 170.

About 55 percent of the home builders said they expect to start fewer houses in 1991 than they did in 1990, and 75 percent said they are building fewer speculative houses than a year ago.

Of the seven main price categories, fewer prospective home buyers are envisioned this year in all but the $375,000-to-$450,000 price range, the builders said. In that category, about half the respondents said they would have fewer buyers and half said they would have the same number as a year ago.

Nearly 70 of the home builders said they were building houses in either the $75,000-to-$150,000 range or the $150,000-to-$225,000 range, and 64 percent of the respondents said they thought the houses they were building this year would be priced about the same as a year ago. About 15 percent said they would be pricing their houses higher than a year ago, and 22 percent said their houses would be priced lower.

In 1990, the home builders said the typical housing site contained 27,455 square feet, down about 16 percent from a year earlier. The builders typically paid more than $43,900 for the lot, or $1.60 per square foot, up about 14 percent on a per-square-foot basis.