Paulgwat

@Nickfromwales thanks, I have gone back to Potton for them to review the drawings as have had to put the scaffolding back up to look at this and don't want to have to do it again

Hi all, I am looking for some help in understanding where i might be going wrong here. We purchased a Potton timber frame and they supplied the attached detail for how the roof should be constructed for the 2nd floor (these are bedrooms and bathrooms with a wall height at the edge of the room of 1.5M and a sloping roof until 2.4M). We have followed the drawing, installing the counter battens as indicated on top of the sarking board and then installed the vapour barrier (Rhinovent Pro) over the top of the counter battens with the 10mm droop as indicate in the install instructions for the membrane. Battens have then been installed on top of the vapour barrier to allow installation of solar panels and roof tiles. We are basically revisiting this as we have issues with water somehow getting in either via the Velux windows or through the membrane itself (to our knowledge there are no rips or tears in the membrane) and running down the sarking boards and finding its way to the wall plate. So my questions are 1. Have i bought a rubbish membrane? What should I use instead? 2. Detail from Potton calls for Kingspan Nilvent (or similar) but all of the information on Nilvent says it should be laid on top of the sarking board and not over the counter battens - which takes precendence here? 3 Does anyone have specific information on how to install a velux window on a sarked roof with counter battening, as we couldn't find anything. I am sure I have left out a bunch of relevant info, so apologies in advance if i have omitted anything important. Thanks in advance Regards Paul