Using slates as cladding for walls must have seemed like a great solution……at first. Slates are an inexpensive material, self cleaning, easy to source and the skills to install them are readily available i.e. roofers. But unfortunately they fail the robustness test. See the photographs below of a building in Dublin where they have been used to clad a wall.
As can be seen from the photographs it can easily become a target for stone throwing vandals and once broken the tile will fall away and the building may be left open to the elements. Assuming a breathable membrane was used to protect against water ingress, this will still be easy to cut and a thief might be able to gain access. So it is a fragile and not very secure cladding. But it is also dangerous.
If one of the broken tiles happens to be over a doorway it makes for a very dangerous situation as it could fall when someone is walking underneath. This would make for a very bad day for the unfortunate person.
Slates are best left on sloped roofs and not walls. See photograph below.