Don't wait until the trunk grows against the deck. Design deck joists to accomodate growth.
Wood cut away to allow space for wood growth. This was Western Redcedar.
Wood decay is not preferrable, but is not always fatal. Fungi conks are evidence of decay.
Bark between leaders has small ridge upward: excluded bark. Better than included bark.
If a codominent stem needs removal, don't cut into the center bark ridge between.
Branch collar on an Atlas Cedar. When pruning to remove limbs, don't cut past that point.
A proper pruning cut leaving the undamaged branch collar intact.