David Adjaye is to design two £5.5 million ($9.5 million) public libraries in Washington DC.

The practice will partner with local architects Wiencek + Associates to design replacements for two existing buildings, the Washington Highlands Library built in 1959 and the Francis A. Gregory Library built in 1961, which will be demolished.

£1.5 million ($2.6 million) of the budget for each library has been set aside for design and the budget has already been allocated by the City Council.

Library officials cited Adjaye's Ideas Store in east London – which the architect himself considers his big breakthrough – as key to winning the pitch.

Ginnie Cooper, DC Public Libraries chief librarian, said: “In the library world we paid attention to [the Idea Stores]. They are in what we would call rough neighbourhoods.”

Community representatives also said they found the fact that Adjaye turned up in person for the design presentation encouraging.

Adjaye said: “What is exciting to me is that they are not in downtown, they are not grand projects, but are in real family neighbourhoods.”

Adjaye’s first major project in America, the Museum of Contemporary Art in Denver, completed last year.