Extending Walls - Wall Layers in Revit
Believe it or not, Revit will allow you to extend or contract selected wall layers above or below their base or top constraints!
This means that you can have one part of the wall assembly at a different height to the rest of the same wall. Let me demonstrate:
Start by creating a couple of Basic Walls, I have used a Double Brick wall that came with the default template. These have a few layers already so they should do the trick.
Select one instance of this wall type and then go into it's properties, now click 'Edit/New' to bring up the Type Properties.
Click the 'Edit...' button to bring up the Wall Assembly editor
Make sure the Preview is open and that the View is set to Section in the drop-down box.
Zoom in (using the scroll-wheel on your mouse) to the bottom of the wall and click the 'Modify' button.
Now click on a line at the bottom of your wall assembly. You will notice a small Lock appears. Clicking the Lock to unlock the layer is how we will define which layers will be extended. You can do this to the top of your wall layers as well.
Click OK, then OK again in the Type Properties dialogue.
You will now notice a new Instance Parameter called 'Base Extension Distance'. This parameter will extend the 'Unlocked' layers a positive (up) or negative (down) value. If you unlocked the tops of any of the layers, you will also see a Top Extension Distance.
I have set the Base Extension Distance of this wall to -500 and the parallel wall to -200, then cut a section through. Note how the unlocked layers have moved down while the others stay at their base constraint.
I can also unlock the adjacent layer in the Wall Assembly, note that you can only unlock adjacent layers. To do anything more complex, you will need to use Stacked Walls. Notice that both unlocked layers now move with the Base Extension Distance. That is, there is only one Base Extension Distance parameter per wall instance.
The Base Extension will work with the Base Offset parameter. In the above picture I have set Base Offset to -200 and Base Extension Distance to -500. As you can see (more clearly), this wall has the two outermost layers unlocked.