We've just removed the Gyprock (drywall) from our walls to install acoustic/thermal insulation and new acoustic plaster. In doing so, we've found that our 1969 home has nothing at all against the outer wall between the brick veneer and the plaster. We can see into the ceiling space above the eaves and down under the house in the gap between the timber frame and floor boards. Additionally, sheets of Gyprock were covered in ants and there were mouse droppings on the noggins.
Before we install the acoustic insulation batts and new plaster is there something we can do to seal and separate the outer wall (bricks) from the inner part (considering the insulation batts as inner)?