Just bought a house with a questionable deck install.

Likely he number 1 job is to flash the deck. It will be a bigger job that I'd like because the deck boards run perpendicular to the house. So I dont have the lux of pulling up a few boards and installing the flashing. And pulling every board is a lot more work. Suggestions?

The number 2 job is the deck ledger board. The house is painted cedar. The wood is in good shape. But the last owner installed 2 boards (exterior sheathing, not HP, wood grain looks stamped, is rotting) below the cedar, butting the joint to the last row of cedar. That added sheathing is sandwiched between the ledger and the end joists of the house. The sandwiched sheathing board is rotting away.

The ledger is bolted to the house using 1/2" lags that don't fully penetrate the joist. I plan to replace them with appropriate carriage bolts.

Question. Should I replace the rotted sheathing or remove it and use a few washers on the carriage bolts to make up the space? If I replace it I will eliminate the but joint and lift and lap under the cedar.