Decals maybe, like other siad. talking abotu decals, I think it can only add ‘paint’ to walls, but not bump or normal.
Edit: YOu can add normal ro decal. See page.
.unrealengine.com/latest/INT/Resources/ContentExamples/Decals/1_2/index.html
So I think you might be right. I don’t know whether the person doing environment has posted it here yet but might be of some interest 
All those details and rounded corners are made with “mesh decals”, it is a very nice tecnique to achieve realism. Some time ago i found a guy who datamined the game from ps4 and extracted the game files and the hallway 3d model and texutres. The main walls texture are very simple and plain but the hallway has A TON of mesh decals allover the corners and walls. If i find the place where i downloaded the hallway file i’ll link it for you here so you can take a look at how the actual game is made. (sorry for my bad english)