This paper presents the evaluation of zinc and titanium nano-oxide silane/siloxane emulsions and their resistance to biofouling by algal colonisation. A culture streaming study was conducted to evaluate each treatment using mortar samples. Characterisation of the treatments included assessment of the porosity, surface roughness, sorptivity, hydrophobicity, treatment depth and visual alteration. The results showed that nanoparticulate incorporation did not adversely alter treatment penetration. Nanoparticulate treatments improved water repellence significantly while effectively conserving the morphology of the substrate. Treatments had negligible impact on visual aesthetics of the substrate making them ideal for future retrofit and heritage schemes. It was concluded that the reduced bioreceptivity observed primarily stemmed from the nanoparticulates ability to photocatalytically breakdown contaminants.