All battens are to be check with spacing no more than 600mm,and runs continuous from top to bottom, if the batten toward the joist and bearer is not level, it may be require be packing out or planning down. Head flashing will need to be installed to all joineries using flexible flashing tape (Aluband) to tape it against the top of joinery and building warp, then lapping vent strip over the head flashing and tape against the building wrap as well. Both side of the head flashing will be fitted with stopper with sealant.