If I fit 18mm full replacement uPVC fascia boards I am required to allow a gap for expansion - 5mm for 5m length I believe. My question is, if I have fixed the board into the rafter ends every 600mm with polytop s/s nails how will the last set of nails be able to move to allow for the expansion. Will they not end up working loose. I dont see any statements anywhere on the web about being obliged to predrill oval shaped holes to allow for this.