Here's a trick I used on my Arcade Hotel to give a controllable "breakaway", with stucco on top and bricks below.

The key is the Spots node, which goes directly to the Bump input and also
controls the stucco (Noise) via the Blender.  The Image Map (not fully visible)
is the underlying brick pattern.

You might want to use a smooth painted surface for the "above" (where I have
the Noise for stucco here) and a rough image for the "below" (where I have the Image
for bricks.)

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