The workshop has been home to the theatre’s costume-makers since the 1950s and is in urgent need of repair.
Work began in February to conserve the 19th century Grade II listed buildings, put in updated facilities and enable it to open for the first time to visitors on site tours.
The redevelopment will create 1,644 sq metres of modern workshop accommodation, mainly over two storeys, for what is the largest in-house costume-making department of any British theatre.
The redevelopment, architect for which is Aedas, will also create a new entrance to the RSC offices and Costume Workshop using the 1887 former scene dock doors which were built for the original Shakespeare Memorial Theatre.
The RSC in Stratford is one of the few theatres to have an in-house armoury where armour and weapons are made, as well as workshops where everything from hats, corsets and leatherwork to jewellery and masks are crafted.
RSC technical director Stephen Rebbeck said: “Our costumes are essential for us to create theatre at its best, made in Shakespeare’s hometown of Stratford-upon-Avon and shared around the world – so we are looking forward to working with Stepnell on the restoration and redevelopment of our Costume Workshop. The project will help us create the best facilities for costume-making fit for the 21st century, as well as offer new training and apprenticeship opportunities and allow visitors to experience our world-class costume workshop for themselves.”
Stepnell operations manager Paul Fish said: “We are extremely proud to be working on this landmark project for the RSC, helping create modern facilities for the theatre’s dedicated and highly skilled costume makers. We are absolutely delighted to bring our own team’s expertise in working on conservation programmes and historic buildings to this exciting project which will transform and expand the workshop accommodation enabling the costume team to continue to produce the award-winning creations which make such an essential contribution to the success of RSC productions.”