Hope all are well, it’s been a few years…

Live in a 1870’s farmhouse in new england.  Original exterior was shiplap cedar, still in amazing shape, nailed right to the studs.  In the 1960’s, previous “build it better yourself” owner overlaid cedar shingles and then added an enclosed  porch.  The problem: the header joist for the porch roof  was nailed directly to the shingles. Water eventually and still does seeps down into the porch…

I would like to remove the shingles above the porch roof line and add shiplap cement siding above the porch.  However, without ripping the porch roof off, how do I get the porch roof/house wall joint watertight. 

Given my tag name, trust all will realize I redid the porch roof (soffits/shingles/most of the sheathing three years ago)…

Regards,

Rerwork