Is there a way to "merge" two extruded regions to one? I have a model as shown below, which is the product of two extrudes, bottom step followed by upper step. These are disjoint which I can see if I select the front face of the upper stair and drag it up, there's even a hidden face between.

Is there a way to merge them by deleting said hidden faces (orange arrow in the bottom image) and perhaps triangulate like I outlined with two lines on the bottom image?

If I had extruded upwards from the bottom step my hidden face would be along the wall instead, so no improvement. (I think it's a non-manifold mesh but https://blender.stackexchange.com/a/7914 does not help here as it selects no vertices or anything).



I could fix this by deleting the two faces touching in the above image and manually recreating the 3 triangles seen below. I was just hoping there was an automatic way to collapse "touching" geometry.
Delete both overlapping faces. Then select the edges on both steps and do bridge edge loops.