Hi Laura,
ok… Right… So in the intervening year, I’ve messed around with various versions when I’ve had time & the inclination.
Who knew it would be so hard?!
Obviously I’m not feeling that there is a perfect version yet, but it does depend quite what you’re after.
As noted above, I went down a different route due to the shear number of pointy buildings I was getting… If it only works for rectangles it seems like a dead end.
However, it that’s good enough for you, here’s a version which works on my PC this morning… Dynamo 2.03 & Revit 2019.2 You will note that it isn’t perfect, as noted above, we need to include references from intersecting walls… But we’ll get there! 
Happy for anyone to chip in and give assistance.
Cheers,
Mark
Dim Walls In Active Plan View.dyn (241.1 KB)
