Walls and Ceilings - plank walls

My home is over 150 years old. We recently remodeled two rooms and discovered that the walls were plank. The planks are about 1.5 inches thick, 12 - 18 inches wide and run from the foundation wooden beam to the beam on which the rafters sit. There are no 2 x 4's in the walls, only these planks, nailed to the exterior(outside) of the beams. They are holding up the house! We have put in vaulted ceilings in two rooms, new 2 x 6 walls and 2x 6 rafters, My problem is that when the front door shuts/slams, there is an annoying amount of movement in the wall the door is in and another wall. Any suggestions?

Hi sherryburdick,Did you do the remodel?You cant just add all that weight to a house,if the foundation cant support it.If a contractor did the job,shame on him,he should know better.You have a serious problem that needs to be address fast.