Tate has raised half of the £45m needed for an extensive refurbishment of Tate Britain with funding from “private individuals and foundations”.

Nine galleries in the southern part of Tate Britain will be renovated as part of the Transforming Tate Britain project, while a spiral staircase will be built in the gallery’s domed atrium.

A circular balcony in the Rotunda dome, closed since the 1920s, will reopen. An entrance and reception for schools will be created, while a ground-floor cafe will be built.  

Subject to planning permission from Westminster City Council, construction is set to begin in March 2011 and is scheduled for completion in 2013.

The project architects are Caruso St John. A spokesman for the Department for Culture, Media and Sport said the department had no plans to fund the project.