Ensure the 'Mesh-To-Roof' add-on is installed.

• Download the ArchiCAD 14 version directly (for Windows) from here
• Download the ArchiCAD 14 version directly (for Mac) from here

(Once downlaoded, ensure ArchiCAD is closed, Install the add-on and then re-open ArchiCAD and the specific Project)

Within the ArchiCAD project:

1. Draw the mesh – the finer the contours, the better the mesh
2. Draw the wall elements approx 5-8m high
3. Drag a copy of the mesh on top of itself
4. Elevate the mesh by the "height of the required wall"
5. Change this mesh's 3D mode to "Zero Thickness" option in the mesh settings dialog (see below)
6. Make a new layer called (for example) "SEO Operators" and hide this layer
7. Goto the Roof default settings and make the roof thickness relatively small e.g. 5mm
8. Convert this mesh element to roof elements using the Mesh-to-Roof Add-on (Design > Design Extras > Create Roofs from Mesh)
9. Go to the appropriate story and group all the new roof elements via Edit > Grouping > Group (possibly turn off all other layers to help selection)
10. Open up the Solid Element Operations dialog from the Design pulldown menu (see the link below for more info on SEO's)
11. Show the model in 3D
12. Click on the walls in the model > Click "Get Targets"
13. Click on all the Roof elements in the model > Click "Get Operators" (they should select as one because they are grouped)
14. Choose the operation type "Subtraction with upward extrusion"
15. Click 'Execute'
16. Change the layers of the roof elements to "SEO Operators" (the roofs will turn off but the operation still applies)
17. Delete the zero thickness mesh

For more info on Solid Element Operations (SEOs), click here to view a PDF