I'm building a small deck against the back of my house. The ledger and joists are in place and I'm about to attach the first deck board parallel to the side of the house. The standard method seems to be to place the first screws closest to the house into the ledger. The top of the ledger is covered with metal flashing however. So would the screw holes through the flashing cause a water leakage problem later significant enough to worry about?