The manufacturing of double-curved precast concrete elements is still expensive, due to the high costs and limited possibilities for repetitive use of the moulds or formwork. The goal of the research described in this paper is to develop a production method that overcomes these difficulties by enabling the mould to be reused many times and by making the shape of the mould adjustable in a flexible way. First the paper gives an introduction of free-form architecture and the issues related to realizing complex geometry in concrete. Sequentially, the paper reports on the structural mechanics models that have been developed to accurately describe the behaviour of a flexible mould material. Finally laboratory experiments are reported, that are based on the concept of deforming an initially flat concrete element into a curved shape after a short initial hardening period. After this deformation process further hardening will take place in the final curved shape. The advantages of starting with an initial flat layer are that no contra-mould is needed, the element thickness can be controlled accurately and the casting process is relatively quick and simple.