How big can I make an underground room before it collapses?

It's a simple question that I haven't been able to get a good answer to. I assume that rooms made of stone can be larger than rooms made of clay or sand.

If I want to make a very larger room, can I place pillars in it to hold up the ceiling? (i.e. Can I just not dig out small sections of the stone, to leave small sections of wall to act as pillars?)

2 Answers 2


In the Current Versions of DF (.34 as of this writing), he Earth, Stone, and Soil of Dwarf Fortress does not obey the laws of physics (yet!).

This means, you never have to worry about collapse, as long as the tiles above you are anchored to something other than simple air. Material has nothing to do with it; dunes of sand can be hollowed out just the same as loamy hills or dacite mountains.

Tiles in Dwarf Fortress have two parts: the tile body and the tile floor. If you mine out the tile body, the tile floor remains. If either of these pieces is wholly disconnected, a cavein will occur. Therefor, you might be causing caveins if you're hollowing out rooms via a combination of dig and channel. Instead, start from the top, and tell your dwarves to Carve Ramps into the layer below. This will hollow out the same area, but removes the risk of dropping floors that channeling has.

  • Actually, it obeys them no longer. 2D version had cave ins if you didn't have enough supports.
    – kotekzot
    Commented Oct 26, 2012 at 17:49
  • @kotekzot good point. 2D predates me, however. Commented Oct 26, 2012 at 18:00
  • @Just to be clear, you both agree that cave-ins won't happen in the newest version? Capnduck mentions something about them in one of his first videos. (It's just a passing comment.) Commented Oct 26, 2012 at 18:30
  • 1
    @theJollySin Correct. Capnduck's videos are quite old. Commented Oct 26, 2012 at 18:44
  • @theJollySin yes, supports for large areas were necessary before and likely will be necessary in the future, but not at the moment. Take advantage of the opportunity to build structurally unsound fortresses while you can!
    – kotekzot
    Commented Oct 26, 2012 at 20:05

Currently, only totally disconnected material collapses. See the cave-in article at the Dwarf Fortress Wiki for lots of details.

  • 2
    Can you highlight the salient points from your link, please? Answers should be able to stand on their own, without requiring a link to fully answer the question. Adding a link for more information is fine, but it shouldn't be the crux of your answer.
    – Frank
    Commented Oct 26, 2012 at 18:55

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