Eco-engineering complex 3D geometries into marine built structures can in some instances increase the biodiversity and ecological functioning of infrastructure. New modular technologies are enabling eco-engineering interventions to be applied on scales of tens of meters, potentially covering the entire intertidal range of structures, and incorporating multiple complex geometries. Different eco-engineering designs tend to support unique communities and thus, incorporating a combination of designs can maximise biodiversity outcomes. However, it is unclear to what extent the patch size of different geometries, and whether eco-engineering is applied continuously throughout the intertidal range or in smaller patches, influences biodiversity. In this study, we investigated whether ecological communities on eco-engineered seawalls were influenced by the patch size of a habitat geometry (e.g. small versus large) and configuration (e.g. located in isolated or connected groups). Results show that patch size and configuration can influence ecological communities, but the magnitude of these effects vary depending on the habitat geometry. Generally, larger patches and contiguous intertidal application of eco-engineering supported more biodiverse communities and effects were more pronounced for designs that retained water and moisture during low tide. These results can help guide eco-engineering design in the future to optimise desired ecological outcomes.