Is sheetrock/drywall required under woodpanelling?
If I am not mistaken I believe there are 2 things that are going to play a role in this when dealing with older homes from the 50s on back.


Meeting fire codes and
Will meeting fire codes endanger the integrity of the dwelling based on load bearing capacities. 


For instance, many homes back then had rooms with wall to wall knotty pine, plaster in place of drywall, load bearing walls made of all bricks with 2 fireplaces to match. Not to mention, was the roof sheeted or were slats used. 

That type of weight starts adding up real fast.

I think a private or city engineer and then/or a city inspector can tell you what the answers are.

Might want to see if you can access the prints of the home if you do not already possess them. It may save you some $$$.

If you get bored or find this interesting here is a link to a live load and dead load calculator. You will quickly see that weight plays a huge factor that is often overlooked when you're talking numbers like 40 lbs per sq ft and a fish tank is in one corner.

http://www.awc.org/codes-standards/calculators-software/spancalc