Mark the position of the top of the deck on the existing siding (usually about 1 to 2 inches below the interior floor).
Use a level to draw a line at this height along the full length of the proposed deck. Measure down from each end of this line to allow for the combined thickness of the decking boards and the width of the ledger board as it hangs on the wall. For example, with 2-by-10 ledger board, measure down 1 1/2 inches for the decking boards and 9 1/2 inches for the ledger board - or 11 inches total.
Chalk a line between these two points. (See "How to Snap a Chalk Line" in the Related eHows.)
Cut along the lines you have just marked with a circular saw. Set the saw blade to cut only as deep as the thickness of the siding on the house. Use hammers and pry bars to remove siding from the area between the lines.
Align the bottom edge of the ledger board with the bottom edge of the cut section. Tack the ledger board in place with 16 penny nails driven only partway in (to allow for easy removal). Check for proper fit all around.
Pre-drill holes through the ledger board and into the side of the house for lag screws.
Remove the ledger board and squeeze silicone caulk (moisture seal) into each pre-drilled hole.
Set lag screws into the ledger board, then mount the board back into place.
Make sure the lag screws are thoroughly tightened, firmly securing the ledger board to the house.
Caulk a thick line of silicone on top of the ledger board.
Slide galvanized Z flashing under the exposed siding and over the top of the ledger board.
Seal gaps with silicone caulking.
Things You Will Need
- Galvanized Metal Z Flashing
- Measuring Tapes
- 2-by-10 Treated Lumber
- 16 Penny Nails
- Caulking Guns
- Chalk Line
- Circular Saws
- Lag Multiuse Screws
- Pry Bars
- Safety Goggles
- Silicone Caulks
- Variable-speed Drills
- Leave equal spaces on the ends of the ledger board if you are going to attach skirt boards later.