Measure the width of the exterior wall with the tape measure. Note the width you want for the balcony.
Measure the 2-by-10 board to the width of the balcony. Make a cut mark and then cut the board with a circular saw.
This will be the ledger. Measure and cut four to six 2-by-10 boards to 6 feet for the floor joists.
Set the ledger against the exterior wall. Drill pilot holes through the board and into the exterior wall by using the power drill.
Insert lag bolts into the pilot holes and tighten with the socket wrench.
Measure the width of the ledger board and make a mark every 1 1/2 feet with the pencil. Place the joist hangers on the marks and secure to the ledger board with screws.
Place the 2-by-10 boards for the floor joists into the joist hangers. Secure the boards to the joist hangers with screws.
Cut pressure treated 2-by-4 boards to the width of the balcony. Place the boards on top of the joists and secure with screws.
Leave a 1/2-inch gap between each 2-by-4 board to allow for expansion.
Place a 2-by-6 knee brace with 45-degree angles cut on the ends to each side of the balcony. These will be used for additional support.
Secure the knee braces to the 2-by-10 boards and the exterior wall using joist hangers.