Mortgage rates declined again this week with 30-year mortgages remaining at less than 6 percent level for a third consecutive week, Freddie Mac said Thursday.

Rates on 30-year, fixed-rates mortgages were 5.81 percent this week, down from the average rate of 5.85 percent last week, Freddie Mac said in its weekly survey. That is the lowest level for 30-year mortgages in more than four months, since they averaged 5.79 percent the week of April 8.

Rates on 30-year mortgages hit a high this year of 6.34 percent the week of May 13. Since then, they have slowly drifted downward, reflecting a significant slowdown in economic activity in the late spring and early summer.

Analysts said the weakness in growth was easing investors' fears that inflation would suddenly worsen and make their bond holdings worth less.

"Mortgage rates eased even further this week in response to a setback in economic growth during June and possibly July," said Frank Nothaft, chief economist at Freddie Mac. "However, we believe the slowdown to be temporary and we expect growth to pick up in the second half of this year."

Nothaft said the low rates were helping to keep sales of new and existing homes at record levels and he predicted "2004 will be another banner year for the housing industry."

The survey showed that rates on 15-year, fixed-rate mortgages, a popular option for refinancing, also declined this week to 5.19 percent, down from 5.24 percent last week. For one-year adjustable rate mortgages, rates dipped to 4.01 percent, down from 4.08 percent last week.

The nationwide averages for mortgage rates do not include add-on fees known as points. The 30-year mortgage carried an average 0.7 point fee this week while the 15-year and 1-year mortgages both carried 0.6 point fee.

A year ago, rates on 30-year mortgages averaged 6.24 percent with 15-year mortgages at 5.58 percent and one-year ARMs at 3.75 percent.

EVENTS . . . "Creating More Livable Cities for the 21st Century" is the title for a lecture from 6:30 p.m. to 8 p.m. Monday at the National Building Museum, 401 F St. NW, Washington. Rodney L. Swink, director of the Office of Urban Development in the North Carolina Division of Community Assistance, is to discuss how downtown development that respects history, culture and place is popular and also economically sustainable. Admission is $17, $12 for students; registration required. Call 202-272-2448; Web site: www.nbm.org . . . A tour of the Cityline condominiums project in Tenletown is scheduled for 2 p.m. to 4 p.m. Aug. 29 as part of a construction-watch tour sponsored by the National Building Museum. Design principal Robert Sponseller and project architect Ari Blumenthal of Shalom Baranes and Associates are to lead the tour. Paid registrants will be told the meeting location; registration deadline is Monday). Admission is $15 plus annual museum membership. Appropriate clothing is required. Call 202-272-2448; Web site: www.nbm.org.

Send realty announcements by e-mail to renotes@washpost.com, by fax to 202-334-5059 or by mail to The Washington Post, 1150 15th St. NW, Washington, D.C. 20071, Att: Business News/Real Estate Notes.