I usually see T&G porch decks on old Victorian houses that have a roof with generous overhang, knee wall instead of railing, and relatively steep pitch of the porch deck. They are sometimes screened-in. Those t&g boards don't see much rainwater. If yours failed, then there is a reason that it failed so maybe something has to change. If you just want to rebuild it the way it was originally built then pull up a couple of boards and see how it was built. Is that metal railing original?