Put this in the category of “The Missing Revit Manual” in the same chapter as “View Discipline“.
Turns out, Wall Function isn’t just an extra parameter to filter by. We just came across this one. When you change the Wall Function to FOUNDATION, it forces the placement of those wall types to be “Depth” and not “Height”.
Did you even know that was a thing? I would say that 99.99% of the time when a wall is placed, it is assumed to go in the positive Z direction, or in other terms, “up”. The good old Options Bar lets you change the placement from “Height” to “Depth” meaning you can make your wall go “down”. Who changes this? Does anyone ever change this?
Anyway, if you change your Wall Function to “Foundation”, you can ONLY use “Depth” which can cause some hilarious errors as you place a wall.
I am confident some of you knew this already, but it’s news to me and it was news to everyone who I talked to in real life (or “offline” as the kids say… they don’t really say that).
The HELP file has nothing that lays out what specifically happens when you change the Wall Function. I guess it’s time to dive in and see what else might change when we adjust that previously-thought-innocuous parameter.