As a general rule, it is best to attach the ledger board directly to the house rim board at the same level as the house floor by fastening through the solid house band into the house floor trusses. If the deck will be built at a different relative elevation than the floors of the house, it will be important to securely bolt into the houses wall studs. If the house has an unfinished basement, you can sometimes locate the floor trusses with a trip inside the house to eliminate any guesswork. If you can’t locate them or they are unsatisfactory for your application, you may need to reinforce the wall by opening the wall to add blocking to ensure a solid ledger connection. This is especially necessary when attaching to the side wall of a garage, which is generally constructed of weaker structural parts.
Once the house’s siding is removed, you will want to check out the wall for any signs of rot or decay. If the wall is obviously damaged, you will need to repair the house wall before proceeding with building the deck. Never attach a deck ledger to a rotten house wall because the fasteners will not be able to make a solid connection.