November's U.S. housing data shows that if a home is a family's castle, more than ever it seems built on an unsteady foundation.

American home prices fell 18 per cent in November versus the same month one year earlier, according to the latest Standard & Poor's Case-Shiller index of housing values.

That means the average American house is 25 per cent cheaper than the decade's peak value in mid-2006.

"The free fall in residential real estate continued through November," said David Blitzer, chair of Standard & Poor's index committee.

A slumping economy, record foreclosures and relatively higher long-term interest rates have conspired to reduce the demand for new homes, experts say.

"There is very little in the economic tea leaves to give economists hope that a recovery is nigh," said Scott Anderson, senior economist at Wells Fargo Inc., a U.S. bank that specializes in the home financing market.

In some major U.S. urban areas, the recent downturn has wiped out most of the capital gains homeowners accumulated in the early part of the decade.

The Case-Shiller measure gauges prices according to an index measure, in this case, with January 2000 equaling 100. The average U.S. home is still worth about 50 per cent more than the first month of the decade.

In Detroit, however, November home prices were nearly 17 per cent below their 2000 starting point and stood at levels not seen since August 1997.

New York homes posted a better performance, up 86 per cent versus 2000. But the year-long slump still has knocked home values in the five boroughs to their lowest level in almost four years.

In Cleveland, current prices are only seven per cent higher than what they were in the year 2000.

In many cases, the average American would have made more money over the past four years by renting an apartment and shoving the rest of his or her cash into money market funds than by owning and selling a house.

Worse still, it could take housing prices another two years before they recover the ground lost from the latest peak to the November prices, according to Case-Shiller data.

Canada's housing market has held up better than the U.S.'s, although December's average valuation was still 11 per cent below the average home price for the same month one year earlier.

But if the average Canadian home retraced its value back to February 2004, that would represent a drop of approximately 27 per cent, down from December's average price of $281,000.