The colorful Washington home of Almas Temple Shriners for half a century, at 1315 K St. NW, will be razed for a new office building as part of one of the most expensive land transactions in Washington history.

A new Almas Temple will be included in the project, however, under terms of contracts signed recently.

According to real estate industry sources, Rouse & Associates of Philadelphia has agreed to pay more than $15 million in cash for about 45,000 square feet of land at the northwest corner of 13th and K Sts. now owned by Almas Temple and Scottish Rite, two Masonic orders. The Philadelphia developer is not affiliated with Rouse Co., a shopping center and urban developer in Columbia.

An Almas Temple spokesman, who confirmed that an agreement has been signed to sell the K Street site, said an office building (with up to 400,000 square-floor retail sites permitted under current zoning) is contemplated but that no detailed planning has been started.

Industry sources said that when all costs of the land sale, including transfer taxes, are added up, the price will be more than $450 a square foot. That compares with $375 a square foot for the YWCA building site at 17th and K Sts. in 1978, a record for D.C.commercial land at that time.

Even more important in terms of future D.C. development, the higher price has been paid for land east of 15th Street and bordering on the previously nondescript Franklin Park, indicating that the march of future development is going east along K Street.

Full office use of the 13th and K location was selected over a proposed hotel-office combination because of continuing high demand for office space in downtown Washington.