@Anonymous
When using wall schedules (quatity and/or takeoff)...as long as 1 layer of the wall remains continuos (not cut by the columns/beams) Revit will continue to compute the wall as a whole element. Example: if you have a plaster/stucco/brick layer which you left running to cover the column/beam ie: the area os the cut core will remain unchanged and cut part not deducted. The accuricy of the take-off schedule is always dependant on the level of detail used.
There are two ways to the above.
- I deally; to have a more accurate take-off quantities I model walls to the closest way they are built. ie: iI do not etirely rely on the multy layer feature of the wall tool to create the complete built up section...In other words I would model the finish layers & the core as two separate walls. Then I would use Join tool to join them and allow inserts to cut through both...going down this road means that one has to model inserts as well as other wall based elements differently (more detailed to fit the purpose)
- The easy way out is to convert the walls to parts and then take-off parts...this will take-off the quantities of the the parts as they are (ie: cut). Although I use parts a lot - namely when phasing - I try to avoid it when it comes to take-offs ... I wouldn't want to convert everything to parts just for scheduling or to avoid modeling more detailed elements.
Up to you which method to pick
IMAGE 1: Scheduling Parts vs Original Wall - notice in the wall schedule the cuts remain not deducted

IMAGE 2: Wall modeled using two separate walls joined