The work presented in this paper is part of a larger project investigating methods of reducing environmental impact, and improving performance, of fired clay brick masonry walls. Brick masonry has been combined with natural, sustainable materials in order to create a construction system that is structurally and thermally efficient. This is being accomplished through a programme of desk based research and physical testing on both small and full scale samples. The sustainable materials chosen for use in the project are unfired clay bricks and hemp-lime. The paper presents initial results from an on-going experimental programme investigating performance of novel hemp-lime and brickwork composite walls. Hemp-lime provides sufficient thermal resistance to act as the insulative material in a wall construction. Due to its low structural strength and stiffness it has not been used in structural applications to date. Results from preliminary testing suggest that combining structural brickwork with a hemp lime inner leaf can result in some structural benefits despite its low strength. This hypothesis has been investigated further at a larger scale. Results of these initial tests are presented.