Roof tile underlays: Watertightness – Tent effect (NT BUILD 488) Posted onNovember 21, 1998July 21, 2020Author Report #: NT BUILD 488 Approved: November 1998 Download pdf Size: 134.87 KB Abstract SCOPE This Nordtest Method specifies a test procedure for testing the watertightness of roof tile underlays resting on a substrate of wood or mineral wool. Categories and Tags