Knauf AQUAPANEL® Cement Board Outdoor is a robust and stable weather resistant cement-based cladding and directly applied thin-coat render-backer board which is an economic alternative to traditional brick and block construction, as well as a conventional render carrier board. Multiple render manufacturers have approved Knauf AQUAPANEL® Cement Board Outdoor as a backer board for their renders, with many offering a complete joint BBA system certificate. Cement Board For Exterior Use With Portland Cement And Aggregate Core.