I FOUND A 'GLITCH' IN REVIT: Draw order matters - Go Figure! 

Not exactly what I thought but still learned alot of new stuff, thanks for your time Mike!

Thank you Mike.

Great tip & trick, more like these kind of videos hopefully. Thanks Mike.

I do not see that as a glitch. Since this is predictable. Draw order is recorded from the 1st click to the last click of your project. I should say from the 1st vertex to the last vertex. Visually, we are creating a building, but on paper we are creating a math equation. And in math we have priority. That's why draw order is important when a geometry affect another geometry. (Which happen A LOT in revit). And that's why we have to cut and paste back in place our ''existing wall'' over the new construction wall to reset the draw order. Same thing will happen with all 3D modeling software that i know. When using 3D software, the order of drawing is much more important compare to 2D (2.5D) software like Revit. But even in a 2D Cad drawing, each vertex are indexed. Even if changing the index order randomly change nothing visually on your screen, the index is needed to build the ''save file'' itself. But i think it's nice to understand what is happening in the background. The index start to effect the final result of your sketch mostly when a geometry will modify, in any way, another geometry. In revit, when you add 2 vertex, you add much more then just 2 (x, y, z) positions. 2 simples vertex can contain pages and pages of information / parameter. Thus, when you manually add 2 vertex on the screen (Wall simple line), Revit generate from 8 to nearly infinite number of vertex depending on how many layer you add in your material list. I've never check what is the maximum number of layer we can create lol You also need to respect draw order when using Model in Place for example. The ''Phase created'' function as not been made to recreate a new draw order. It's just for visual effect.

Great

It would be great if you make a tutorial about this, a complete small building modeling in Revit.

A SMALL PROJECT, HOW TO USE PLUMBING USING ARCHITECTURAL TEMPLATE?

This glitch happens regardless of the drawing order.

at 13:40 you say "grab your existing walls, cut'em out of the plan and paste them back in". Shouldn't it be 'grab your new walls.." ?