To replace conventional toxic variants, hydroxylterminatedpolydimethylsiloxane (PDMS) with different viscosities and concentrations were incorporated into aqueous emulsions. Physical stability and thermal stability was assessed through centrifugation and thermal conditioning respectively. Relevant rheological properties were used to help further understand stability mechanisms. The colour, gloss, water contact angle and treatment depth were also assessed to characterise imparted performance to terracotta roofing tiles. Improved water repellence with concentration and chain-length respectively was achieved. The treatment depth and stability results showed that a silane/siloxane balance was required for optimisation. Emulsions did not alter the visual aesthetics of the substrate significantly.