Welcome RCB,

Not to familiar with Canada and their provinces and such. are we on the same latitude from its original home to the new one? First thoughts and (in my opinion) if their is no decay and it has been standing since 1840.... put it back together and work around it. it has worked this far.

By the way if a structure has been standing from 1840 and it doesn't meet current requirements than the current requirements are bogus (in my opinion).

p.s. yes purlins

p.p.s. what is a swing beam?

p.p.p.s if you can somehow propose that you are extending the life of something old, you might find a loophole to shoot down "current" requirements.