Underdecking Rain Carrying System Installation

1. Make sure your ledger board (main support board attached to house) is properly secured and flashed. There should be a minimum of 8” of flashing out from ledger board (FIG.1-A) . If flashing does not extend past the gap between the first two deck boards, install gutter along ledger board after Underdecking  is installed.

2. Mark your chalk line nearest the ledger board. Measure 3-1/2” out from the ledger board on opposite sides of deck, and pop or snap chalk line (FIG.1-B). This mark will be your “center” mark for positioning the joist brackets.

3. Mark your outermost chalk line. Measure 3-1/2” out from the beam on opposite sides of deck and pop or snap chalk line (FIG.1-C). This mark will be your “center” mark for positioning the joist brackets.

4. Proceed to snap the middle chalk lines. Beginning with the ledger board side, measure, mark & snap chalk lines every 20” apart (FIG.1-D). Again, this mark will be your “center” mark for positioning the joist brackets. Spacing between rows should not exceed 20”, including the last row.

5. Before installing joist brackets, place a level on the joist in several locations to make sure deck is level or pitched toward drainage direction of system. (Inconsistent or bowed joist are covered later in these instructions.)

6. Install first joist bracket by aligning the center of the joist brackets with your chalk line. Start in middle of first joist by fastening bracket with male keystone snap closest to outer perimeter joist. Make sure center of bracket is lined up with chalk line.(FIG.2-A)
Use 2 1/2” screws for rows 1-5, and 3” screws used on rows 6-8.(FIG.2-B)