Can creatures move diagonally through walls?

Question

I've told my dwarves to build a protective rock 'sheath' around my column of up/down stairs (thrust to the floor of a cavern) in the following pattern:

OOOO
RXXO
RXXO
OROO

O = Wall build order R = Rock X = Stairs

But they've decided (in their wisdom) to leave the parts above cavern-ground-level as such:

OWWO
RXXW
RXXW
ORWO

W = Wall

Since the walls are preventing my dwarves from completing the building, will they also stop bats and other horrors from getting in and scaring my dwarves away from my main (and only) staircase?

I know, I know, I should have put preventative measures in place before breaching the cavern, but it's my first time!

Answer 1

To answer your first question, yes, all creatures can move diagonally.

Your underlying problem is with the order of the designations. Dwarves operate on a Last in First Out system (LIFO) which means that for squares, if you, intuitively, mark all four walls at once, you'll get one corner (if you went clockwise) or a variable amount (if you went horizontal -> vertical or vice versa) that can still be less then four.

Once this has happened, you must deconstruct walls to reach the corners, as construction can't happen diagonally.

Prevention of this is actually pretty easy as long as you're aware of it: simply build corners first, either by not assigning other construction jobs until the corners are complete, or by suspending one or more adjacent wall constructions until the corners are complete, then unsuspending them.

Answer 2

Things that can move/be done diagonally:

• Water
• Creatures
• Digging
• Deconstruction of buildings

Things that can not move/be done diagonally:

• Miasma
• Construction
• Structural Integrity

This is not a comprehensive list.

Answer 3

Dwarfs and other creatures will happily move diagonally. In your case I would tear down those walls and rebuild the corners first. The only thing special I can think of is that given a flood, diagonal moving water looses pressure.