18mm replacement fascias do not require a backing board - they are a straight replacement for old timber fascias, as they are nailed directly onto the rafter feet.The industry name for replacement fascias can appear misleading, as nowadays these boards are commonly used on new build projects.Our black smooth finish fascia boards are available in a wide range of widths including 150mm, 175mm, 200mm, 225mm, 250mm andamp; 410mm.The return leg on the board is slightly rebated to accept a soffit board.