Hi Im new to forum so any help greatly appreciated. Plan is to lay 100 pir over ex ground floor felt roof 12'x8' (cracked but not yet leaking), then new osb deck folowed by grp system.
Do i need to fix new osb through pir (using long screws into ex joists) as this would seem to stop any expansion taking place? how to prevent uplift etc without fixing down.
thanks in advance