Two Options:
1. The Roof's Building Material Intersection Priority must be stronger than the Wall's.
2. Use Solid Element Operation > Subtraction with upward extrusion to remove the upper part of the Wall.
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David
David Maudlin / Architect www.davidmaudlin.com Digital Architecture AC27 USA • iMac 27" 4.0GHz Quad-core i7 OSX11 | 24 gb ram • MacBook Pro M3 Pro | 36 gb ram OSX14