There is still one crucial detail you must attend to. The situation is as follows. If the ledger were attached directly against the wall, so that the back surface of the ledger was tight against the wall, rainwater running down the wall would get trapped between the wall and the back surface of the ledger. This would cause rotting. The easiest way to do this is to install washers on the lag screws between the ledger and the wall.
Galvanized metal touching aluminum causes corrosion.
These washers will leave an adequate gap. After you have threaded the lag screws into the ledger, installed the proper number of washers on each screw, and squirted caulk into the holes, lift the ledger into place, tap the screws into the wall, and, with a socket or crescent wrench, tighten the screws. You are now ready to install the two edge joists and locate your pier holes. If you are using pressure-treated lumber or a decay resistant lumber that is not all heart, we recommend that you paint a waterproofing on the cut ends of the ledger and all other exposed boards. Click here to receive up to four Free estimates from prescreened and insured contractors.