This paper discusses laboratory tests on Lower Oxford Clay (LOC) stabilised using different levels of lime (L) or Portland cement (PC), with and without blending with ground granulated blast-furnace slag (GGBS). LOC is used by Hanson Brick Company Ltd in the manufacture of fired ‘London’ bricks at the Stewartby brick plant in Bedfordshire. The research investigated L–PC, L–GGBS and PC–GGBS blends to assess their potential for application in sustainable unfired clay building materials (bricks, mortar, etc.). Use of unfired materials reduces not only energy costs, but also environmental damage associated with the traditional firing process used in the manufacture of clay building components. Due to the high strength requirements of the building industry compared with, for example, stabilised highway pavement layers, a high maximum stabiliser dosage of 20% was used. For road construction, typical stabiliser dosages are 3–8% for lime and 3–5% for PC. In the current investigation, cylindrical test specimens were cured for 28 days at moisture contents of 25, 30, 35 and 40% before testing for unconfined compressive strength. Preliminary results show that the strength values for all stabilised material investigated was within the strength range of 737–2077 kN/m2 at 28 days, with L–PC blends tending to achieve lower strength values than L–GGBS blends. Overall results suggest that there is potential in using GGBS-based binders for the manufacture of unfired building components.