Trying to do a simple Boolean shatter on a building model.

I've attached 3 pics.
In the 2nd and 3rd you see BEFORE and AFTER the Boolean operation with the building geometry.
It seems that the actual grid geometry used for slicing the building is becoming part of the result, but I have no clue why.

Even though it appears to work with my source geometry set to Surface, I assume the result will be incorrect. Saw this thread about bad topology when using the Boolean SOP https://www.sidefx.com/forum/topic/49549/?page=1#post-224078 [www.sidefx.com]

If I do as suggested and use a PolyDoctor SOP to ‘Visualize Maximal Manifold patches’ then I get multicolored geometry (first attached) . Question is how do i correct this?

I guess you have to start from whatever your Boolean SOP is complaining about
but if your geo A is not solid then you better treat it as a surface, but then you will not get any internal faces
so maybe instead just ensure that all your input pieces are watertight and have correct winding on polygons