I think it's mostly a liability issue. It was built 200 years ago most likely using what we call here "the farm method" which is basically "eye balling" or guessing what sizes to make the members based on experience. Now that it is used as part of a historical landmark that is visited by the general public, I am guessing that it will need to meet at least some (if not all) of the current codes. The owners have hired us to advise in the repair and restoration which makes us liable should anything fail. The loads used from today's codes have built in safety factors and can be quite conservative at times which is why I am wondering if there any other factors involved for these kinds of situations. I will get in touch with a PE as suggested.
