Begin building a deck on a sloped sight by anchoring the ledger.
Most decks are attached to the house with a ledger because it easily adds strength to the structure. In some areas with unstable soil, however, a deck must be unattached to prevent damage to the house and deck if it shifts.
Make it level and strong
The ledger will act as the reference point for laying out the entire deck, so take time to position it precisely and level. If the siding or door is not level, you may be tempted to install the ledger out of level for appearance's sake. Resist the temptation: An angled ledger greatly complicates the rest of the construction process.
Attach the ledger with lag screws driven into framing members -- not just into the sheathing. Most homes will have an exterior joist (sometimes called a band joist) just below the door sill. That's where the ledger goes. Drill test holes to make sure the screws will have a hefty 2x board to grab.
Four to five hours to cut and install a 16-foot ledger board on a frame house; longer to attach to masonry
Layout square, tape measure, level, circular saw, hammer, drill, socket wrench
Measuring and cutting boards, testing for level, driving lag screws
Draw the exact location of the ledger on the house
Ledger board(s), lag screws with washers, shims if necessary
Mark the outside edges of the ledger on the siding.You may be able to remove siding. If you are cutting the siding, extend this mark 1-1/2 inches (the thickness of the rim joists) past the actual length of the ledger on each side. This will allow you to fasten the rim joists to the ends of the ledger.
Cut the ledger board and the header to length. The header is usually 3 inches longer than the ledger because it's fastened to the ends of the rim joists. If you need to notch the ledger for an obstruction, use a circular saw, stopping just short of the corners. Finish the cuts with a handsaw.
Check indoors to make sure lag screws will not hit any gas or water lines or electric cable. Counterbore pilot holes if you want recessed lag screw heads. If possible, avoid your joist marks. Then drill through the ledger only, with a bit slightly smaller than the diameter of the lag screw threads.