It's extremely useful to use wall styles when you're creating the project. If you are…
Vectorworks Tip 395 – Wall Styles for Additions and Alterations
If you use Wall Styles for drawing the existing building you might end up with several wall styles for all the different wall thicknesses. Then, when you want to demolish any of those walls – you have to create copies of these wall styles. It’s better to use unstyled walls for the existing and set the wall to use the graphic attributes of the class. Then when you want to demolish the wall just change the class of it.