Retired architect Leon Chatelain Jr., one of 30 founding members of the Washington Building Congress, will be on hand this evening when the organization of architects, engineers, planners, contractors, subcontractors and material suppliers holds its 40th anniversary dinner-dance at the Kenwood Country Club.

Born in 1902 in a house on the site now occupied by American Broadcasting Co. on Connecticut Avenue NW, opposite The Mayflower hotel, Chatelain has worked and lived all his life in a seven-block radius of his birthplace. For the past 17 years, he and his wife have lived in a town house in the 1800 block of 23d Street NW.

Since his retirement three years ago from the firm still known as Chatelain, Samperton & Nolan, the tall architect has remained active on boards and committees and has traveled abroad whenever possible.

Chatelain qualified as an architect and later as a member and national president of the American Institure of Architects without formally getting a degree in architecture. He studied at George Washington University (where he recently served a year as trustee) and earlier had taken mechanical drawing and architecture courses at McKinley Technical High School. During his draftsman days Chatelain worked with architect Arthur B. Heaton here.

Some of Chatelain's achievements were in the area of barrier-free architecture. He told the Washington Building Congress magazine that his interest was heightened by his service on the President's Committee on Employment of the Physically Handicapped. He also worked for the D.C. Society for Crippled Children and the National Easter Seal Society for Crippled Childeren and Adults.

Two of his earlier assignments took him to Berlin and he recalls having made 54 trips to Germany over an 11-year period.

The Chatelains have a daughter and two sons, one of whom, Leon III, is an architech with an office in Georgetown.

As to his view of the Washingyon Building Congress, Chatelain recently wrote: "From an association primarily concerned with protecting its own> we have become an adviser to which federal and municipal groups turn practically as a matter of course for guidance and leadership. We have met that responsibility admirably."