In addition, the First Street wing of the Russell Building was built and the Capitol Power Plant was enlarged. Lynn prepared preliminary plans and cost estimates for the construction of the Dirksen Senate Office Building. The Capitol Grounds were again expanded and underground parking for the United States Senate employees was provided. Lynn also supervised a major remodeling of the House and Senate Chambers between 1949 and 1951. David Lynn retired on September 30, 1954, and died in Washington D.C., aged 87.