This technique is for wainscot, or glazing areas where the trim of multiple window units runs together. Short version: a thin wall with empty openings. It's a good example of 'throw down and fix'. Here's the subject structure:
In the ArchiCAD library, there are niche objects, such as W Niche and W Niche Round. These are actually windows. They are built on the WALLNICHE GDL statement. The trouble with these niches is that with the Doors & Windows display option set to Hide on Plan or Reflected Ceiling, they appear to be full, through-wall openings. In addition, they may not handle composite walls correctly.
This is fine:
But when you turn the Doors & Windows off, you get a misleading graphic:
Instead, try a slab and an SEO subtraction.
Start with a polygon wall in the shape of the firebox and chimney plan. The height should be the height of the firebox opening. The fill should be rubble, assuming stone veneer.
1 Stone polygon wall
Instead of cutting a hole all the way through the grade mesh, use slabs on the X Site Cutting layer to subtract material to the proper depth.
Place layout lines where you plan to split the wall.
Solid Element Operations allow you to modify the geometry of one element using the geometry of another. You can add volume, subtract volume, get the intersection of two volumes, or subtract upwards or downwards with a volume.
SEOs make several things that used to be hard easy (true roof thicknesses with nice eaves), and some things that used to be practically impossible possible (differing materials at a slab's perimeter and a hole).
As follows...
Here goes...
When you put a regular hole in a slab, the hole edge material is the same as the slab outer edge. This is a problem, since the slab can't clean up to walls of different materials. Using SEOs instead makes it possible to have a different material at a hole. The key is the option for new surfaces of target to 'inherit attributes of operator.'
Yes. Perfect. If you're into that sort of thing. It takes some doing.