Walls that are constructed of concrete block, that need to be covered with a roof, will require the use of a ledger. A ledger is a horizontal board that is attached to the top of the the wall. The ledger is needed to properly attach the perpendicular roof trusses to the top of the structure. You will need to install the ledger before you can attach the roof trusses to the block wall.
Measure the width of the block and the length of the wall with the tape measure. Measure each wall of the structure. You will require a 2-by-6 or a 2-by-8 boards for the ledger.
Measure the board for the length of ledger for the wall. Cut the board to the required length using the circular saw.
Measure 1 1/2 inches inward from the long edge of the board. Make a mark with a pencil on each end of the board. Place a chalk line on each mark and snap a line. Repeat this step on the other opposite edge.
Measure down the length of the chalk lines and make a mark every 12 inches with the pencil. Drill pilot holes on each mark with the power drill using the 1/4-inch bit.
Set the ledges on top of the block wall. Drill into the block through the pilot holes, using the 3/16-inch concrete bit. Drill into the block to a depth of 1/8 inch.
Remove the ledger board and lengthen each hole to a depth of 1 3/4 inches.
Set the ledger back on top of the wall. Secure the ledger by driving a concrete 3 1/2-inch concrete screw into the block.
Measure and mark the location of the roof trusses. Set the roof truss on each mark. Secure it with a joist hanger using the hammer and nails. Repeat this step to attach the remaining trusses.