When William L. Slayton told the American Institute of Architects at the recent convention in San Diego that he planned to leave his executive vice president post at the end of this year, his was the fourth such announcement by a housing industry executive in a year.

Recently, Oliver H. Jones decided that he'd had it as executive vice president of the Mortgage Bankers Association. For all practical purposes he's gone, but his tenure continues through the end of October.

Earlier this year, Nathaniel H. Rogg dropped the executive vice president reins of the National Association of Home Builders. And John Martin resigned last January as president of the Manufacrured Housing Institute (the mobile home folks). All had felt the heat of members who wanted to play more activist roles. Members who, in some instances, resented the prestige and money their staff executives were getting.

Slayton, 60, told the architects that he wanted one more career. He came to Washington in the 1950s to work on the redevelopment of the South west and stayed to build his own I. M. Pei-designed, triple-arched house hidden by a wall in the 3400 block of Ordway Street NW.

In the Kennedy administration, Slayton was head of federal urban renewal in the housing agency that preceded HUD. He has been AIA's top executive staffer since 1970 and saw the new headquarters building completed behind Octagon House. A man with his savoir faire and talent will find something to do.

Meanwhile, Oliver Jones is preparing to move into a big contemporary house that he and his wife had planned as their eventual hideway in Glade Spring, a development of two dozen 10-acre estates atop a mountain in Bedford County. Pa. The year-around residence has a living-room with a cathedral ceiling over two levels of windows around a huge fire-place. Jones has a study overlooking a manmade lake and will make the home his base for consulting, writing andworrying about inflation.