Learn how to locate deck footings when the yard slopes away from the house.
To locate deck footings when the yard slopes away from the house, you must first measure out from the house along a level line, then down to the ground along a plumb line. This is difficult to do using mason's lines and batterboards. Instead construct the outside frame of the deck, temporarily support and level it, then measure down for the footings.
This method may seem tedious, but actually it will not consume a lot of time. You must build the frame anyway, so you might as well do it now.
Though the supports are temporary, make them sturdy because they need to hold the frame still while you work on it. You will reuse one of the supports later. The 4x4s used as temporary supports can be used later as permanent posts for the deck.
Four or five hours to build a frame, support it, and measure down to locate the footings
Tape measure, framing square, mason's line, hammer, circular saw, drill, sledgehammer, plumb bob, post level, carpenter's level or water level
Measuring and cutting boards, fastening with nails or screws, working on a slope
Install the ledger; consult the framing plan to determine the exact dimensions for the outside joists and the header
Joist lumber, 16d galvanized nails or 3-inch deck screws, stakes, 4x4s for temporary supports, 1x4s for bracing
Cut the rim joists and the header to length. Lay the pieces on the ground and fasten the rim joists to the header with two or three screws or nails at each joint. Set the frame in position and check it for square, using both a framing square and a 3-4-5 triangle. To keep the frame from going out of square, screw a 1x4 brace at both corners, driving two screws into each joint. Use scraps of lumber to support the frame near the header so they will be at the same height as the header.
To make a temporary support, place a piece of 1x lumber about 2 feet long on the sloped ground. Set a 4x4 post on top of the board, hold it plumb, and use a 2x scrap as a guide to mark its bottom for cutting, as shown. Cut the post and attach it to the board with angled screws.
Temporarily brace each support post with 1x4s and stakes. Raise the frame so it is level. Attach the rim joists to the ledger with one screw at each joint. Slide the temporary support assembly up against the header and anchor the support with stakes as shown. Fasten the header to the support post. Estimate the footing locations and install batterboards at both ends of the frame. Attach mason's lines to the batterboards.