Quincy construction firm Lee Kennedy Co. Inc. and Boston-based architect Einhorn Yaffee Prescott have been chosen by The National Archives & Record Administration to renovate and build an addition at the John F. Kennedy Presidential Library and Museum in Dorchester.

The two companies were selected from a nationwide contractor search to work on the $16.5 million project. About 20,000 square feet within the library and museum will be renovated, and a new 30,000 square-foot addition will be built to house artifacts and documents previously stored off-site.

Renovations will include archive and artifact storage areas; support space; offices; security areas; exhibit space; the main lobby and gift shop and some deferred maintenance.

The museum and library will remain open and fully functional throughout construction.

"We are excited to be a part of this prestigious project," said Lee Michael Kennedy, president & CEO of Lee Kennedy Co. Inc. "I am confident that our team’s experience and attention to detail will be integral to our success in updating this Boston landmark."

Preconstruction planning is currently underway. Work is expected to begin early next year, with completion scheduled for fall 2011.