Joist spacing of 400mm centres is recommended for normal residential and light commerical use. On heavy commercial bridges, balconies, moorings, doorways, steps and public areas – use 300mm spacing. If you need to cut Millboard down along the length, then reduce the joist centres accordingly.
A Minimum of 3 joists are needed for any cut boards. When laying 45 degrees to the joist we recommend a maximum of 300mm centres and 240mm centres on commercial applications. For full installation guidelines please refer to the documentation available for download from the Installation Guidelines page.