How to Flash Along Siding

Cover the ledger board, as well as any window frames and the upper eaves of the wall, with a row of flashing before you install the first row of siding. Flashing is sold in various formats based upon where it is installed and in all cases should be installed with a caulking adhesive rather than nails as punctures will cause eventual leaks.

Cut the tip off a tube of caulk with a utility knife so you have a roughly 1/4-inch opening in the tip of the tube. Insert the tube of caulk into a caulk gun and push the plunger tightly into the tube. Use the caulk gun to apply caulking to the flashing pieces, pressing them into place along the ledger board, window frame and the eaves of the house. Cover any seams with more caulking.

Start at the bottom with the first row of paneling and work your way up. Install the siding, according to the manufacturer’s instructions that vary based upon which type of siding you are installing. Lap siding does not need flashing, but paneling will need horizontal rows of flashing. Stack the first row of siding so it sits on top of the ledger flashing.

Install Z-flashing along the upper ledges of any panel siding rows. Run a bead of caulk along the top edge of the siding panel, as well as on the wall surface just above where the first panel ends. Press the Z-flashing into place so that it sits in the caulking adhesive on top of the panel and against the wall. Stack the next row of paneling so that it rests on top of the flashing and locks in place. Repeat the process for each subsequent horizontal row.