There may be in some instances where cavity walls and other layer type walls do not behave as you would like when joining to a certain core boundary set. In the following example I have a 280mm Cavity Wall with the following layers; Exterior Finish, Brickwork, Cavity, Brickwork and Interior Finish.
The desired result would be that the 90mm brick wall not to pass though the cavity. We can use the Disallow Join command, but you will be required to do this for all the walls with this join condition. On the other hand you could remove one of the functions of the layers that make up the wall in order for the walls to join as required.
In the example below you I have removed the function of exterior layers resulting in the wall joins to clean up as shown in the picture.
