The housing market in the Phoenix metro area continues to tread through troubled waters.

According to a new report from the W. P. Carey School of Business at Arizona State University, the median price for an existing home in the Valley fell for the third straight month. Making matters worse, foreclosures continue to weigh down activity in the existing-home market.

The median home-resale price for last month was $135,000 — $3,000 less than August 2009. In fact, existing-home prices have been falling steadily since May, when the median price was $144,000. The median price was at $143,000 in June, and $137,500 in July.

“Although current interest rates and home prices are very attractive, homeowners don’t seem to be motivated to buy,” says Jay Butler, an associate professor of real estate at ASU. “This lack of motivation can be attributed to anemic economic and job recovery, low consumer confidence and stricter underwriting guidelines, among other factors.”

Home sales last month were particularly sluggish, with 4,800 homes re-sold. That’s down from almost 5,100 in July. In August 2009, almost 6,000 homes were re-sold. The numbers aren’t expected to improve anytime soon as home sales traditionally slow down after the summer season.

“As the year comes to an end, median prices often decline in response to holiday and school activities that allow little time or desire to buy a home,” Butler says. “Beyond the impact of foreclosure activity, the absence of a strong move-up market, will also limit any growth in home prices.”

The other barometer of the Valley’s existing home market — foreclosures — fared just as badly in August. Foreclosures accounted for 45 percent of the existing-home market last month, the highest percentage since January.

“When you add in re-sales of previously foreclosed-on homes, all of this foreclosure-related activity represents a full two-thirds of the market’s transactions in August,” Butler says.

About 4,000 foreclosures were recorded in Maricopa County in August, up slightly from about 3,900 in July. In August 2009, 3,100 foreclosures were reported.