Thanks for your response, it's much appreciated. I'll see about getting a couple of images, but it certainly sounds like it (I Googled it, and it's the spitting dabs). Is any asbestos used (probably a 50s construction)?
I'm not a roofer, just an ex-engineer dad with lots of decent DIY skills...
Basically a 6m x 2.5m outbuilding front half belongs to one house, back half to next door. Each half has a narrow (coal?) Room and a bigger shed/utility.
Each half has a slab roof, with a thin layer of concrete (I think). It's about 2" thick and its middle, the mass, looks like shredded...