Hello! I am somewhat new myself, but while experimenting, I have gotten something similar to what you are asking with:
- Blending a grunge map, and perlin noise
- Then a directional warp
- And adjusting with levels and perhaps a gradient blended with that.
Try that and see where it gets you. You can also try masking out that initial grunge map and noise blend before continuing if you want to isolate your sag in the brick to the lower region.