Surrounded by luxurious neighborhoods of large new homes, Stuart and Lisa Carson's 30-year-old rambler was nowhere near the handsomest home in its Sammamish neighborhood.

Still, there were frequent hints that the three-bedroom house, all of 1,560 square feet, might not be the wallflower it seemed.

"We had a note, probably every three months, on our door saying, 'Call me if you're interested in selling,' " Lisa Carson recalled. When that time came early last year, it sold immediately, delivering 9 percent annual appreciation on the home the couple had owned five years.

Meanwhile, 5-year-old homes nearby — bigger homes with fancy new amenities that the Carsons' home didn't have, on streets with sidewalks, which the Carsons' street lacked — also were selling. And predictably, they were going for many thousands more than Stuart and Lisa Carson got.

But the profit their owners realized told a different story. In case after case, these newer homes dotting the Sammamish Plateau realized significantly less annual appreciation — usually 2 to 4 percent — than the Carsons' nearby rambler did.

A Seattle Times analysis of last year's home sales shows that this was no fluke. New homes may have the latest of everything, but as an investment, a new house simply does not bring the returns that an older home does. Countywide over the past five years, new houses have posted 4.8 percent annual appreciation, while older homes saw about 7 percent.

In the past year, new houses appreciated 7.5 percent compared with old houses' 10.4 percent.

Based on cost per square foot, the most accurate measure of home appreciation, King County's new houses are actually 20 percent cheaper than older resales.

So if you want more house for your money, buy new. If you want something that will appreciate faster, buy a resale.

This apparent "old house premium" is contrary to what the National Association of Realtors considers customary. It calculated that existing-home prices throughout the country rose 9.3 percent last year, while new-home prices rose 12.6 percent.

The question is why King County is different, particularly when new houses are scarce and logically should be more valuable.

Last year, builders added 3,577 new houses in the county, according to Hanley Wood Market Intelligence, a California-based housing research firm. If all sold during the year, they would comprise 1 percent of single-family home transactions.

Last year, the median price of a new house was $383,010, and that house measured 2,590 square feet, The Times analysis found. ("New" is defined as any single-family home that was sold either the year it was built or the year after.)

Resale houses were smaller — 1,720 square feet — and cost less — $314,900. All numbers are median, meaning half are higher, half lower.

But here's the surprise:

Old houses had a median square-foot price of $186.59, significantly above new construction's $156.11.

It didn't used to be that way. A decade earlier, both were slightly less than $100 a square foot and less than a dollar apart. Starting in 2000, resales' square-foot price began pulling ahead, and the gap has been growing since.

Gopal Ahluwalia, research director for the National Association of Home Builders, knows of no national research into the relationship between new and resale house prices. But he was surprised to hear what The Times analysis found.

"I would think new would appreciate better than old because you don't need to replace the floor or the roof, and the design is better," Ahluwalia said. "There's more openness in those homes, and you pay for that."

Still, he and others said there are plausible explanations for the disparities between new and resale.

The reasons range from the size of new-home lots — as small as 3,000 square feet — to the charm of vintage, detail-rich houses. (Another Times analysis revealed that homes built between 1900 and 1930 cost the most per square foot.) Others point to builders' efforts to keep new homes' costs down.

But the two reasons mentioned most often are location and demand.

Redmond-based real-estate appraiser Alan Pope said neighborhoods within the urban core, which he defines as downtown Seattle, Bellevue and West Redmond, "have a greater number of buyers vying for houses than in outlying areas, whether it's Kent, the Sammamish Plateau, Marysville or Monroe."

There's a practical reason for that. Urban cores, which have the most houses to choose from, are where jobs and major highways meet, meaning shorter commute times.

Also found in urban cores are old homes that, thanks to updating, are old in name only. Remodeling is a $200 billion-a-year industry and so prevalent here that it can easily skew old-house values upward. Just ask John Gaynard.

Last year, Gaynard sold his 25-year-old South Bellevue home. Judging by the sales price, the house registered 12 percent annual appreciation in the five years he'd owned it. Meanwhile, nearby new houses appreciated from 2 to 6 percent annually.

But Gaynard believes that 12 percent is misleading "because we put $150,000 into it," replacing the windows, roof, siding, cabinets and doors.

"It was all name-brand stuff, too," Gaynard said.

The other thing about urban-core neighborhoods, Pope said, is that many are 100 percent built out. Indeed, last year only a small fraction of King County's 3,577 new homes were built within Seattle or Bellevue. Most were in outlying areas, particularly South King County and areas east of Lake Sammamish.

"Where they are building new homes, they can add more supply, and that can keep prices down," said Matt Deasy, general manager of Windermere Real Estate East. "But they're not adding any more houses in the Central Area by Garfield High School, where you have huge appreciation."

According to The Times analysis, areas with plentiful new houses have seen the lowest five-year appreciation rate. In the Preston-Fall City area, for example, 42 percent of the homes are new; in the Novelty, Ring and Union Hill areas on the Eastside, 32 percent are new. Their appreciation rates are on the lower end: 3.9 percent over five years on a square-foot basis, compared with the county average of 6 percent.

Finally, appraiser Bob Chamberlain, a senior associate with Bruce C. Allen & Associates, thinks the difference in new and resale appreciation can be explained partially by the sales prices of each and the number of buyers vying for them.

New homes tend to attract repeat buyers who have the equity to swing big down payments. Renate Gordon, a sales agent in the new Talus community near Issaquah, where new $600,000-plus homes are going up, said all the buyers she sees previously have owned one or more homes.

This 1,560-square-foot Sammamish Plateau rambler was built in 1972. It sold in 1999 for $225,000 and again in 2004 for $350,000. The square-foot price was $144 in 1999 and $224 in 2004. Annual appreciation: 9 percent.

Older houses tend to be priced lower, in part because they average 870 square feet smaller than new ones. This makes them affordable to more buyers, particularly first-timers struggling to gain a toehold in an expensive market. Lured by low interest rates, they're buying homes in record numbers.

"Starting five years ago, we've had ongoing pressure on entry-level housing," Chamberlain said.

Lisa Carson thinks that pressure is exactly why her 1,560-square-foot Sammamish rambler appreciated so much and sold so quickly.

"It was a good layout, and it was small, so it appealed to first-time buyers and empty-nesters," Carson said. "There aren't many homes that size and on half an acre of property in that area."