What the title says. I couldn’t find an answer in the forum, and I’m unsure about it, since all weapons I checked have a main damage (slash/crush) plus a little bit of the other. Some have a significant value in both damages, like the heavy warhammer (25 slash / 54 crush). How does this work? When you strike a slashing attack (leftclick/RT) do they both apply and check vs armor separately?
Maybe, you meant blunt?
In a way, they do and in a way, they don’t. But it would be more correct to say that they inflict different types of damage. From what I could observe in the game, they don’t mathematically add-up. “Slash” is essentially cutting damage. “Blunt” is what it is: blunt damage, like concussion. It is easy to observe when you fight an opponent in full plate: you can numb your right hand (I’m assuming a right-handed person with a mouse) trying to fight him with a high-slash/low-blunt damage weapon, but take a low-slash/high-blunt one, and it becomes a matter of several good hits. This is especially revealing, when the raw number of the blunt characteristic is lower than the raw number of the slash one. It works more effective even if the blunt number of your hammer is lower than the slash number of your sword. As you can see, in this case they don’t add-up. On the other hand, if you fight a lightly-armoured opponent or a person only in common clothes, they essentially add-up, but in fact they just inflict both types of damage with the same effectiveness.
Re-read what I have written, I can say the same thing much shorter: they are checked vs armour separately 
BTW, this is very realistic.
Thanks for the replies! I get it, and it makes total sense. This makes the heavy Warhammer quite awesome stats-wise, doesn’t it?
Absolutely!