I have a 3x3 column of up-down stairs that I've dug out, and accidentally broke through to the caverns before I was ready. In trying to block the bottom, I dug out the bottom set of up-down stairs and tried to replace them with an up stairs construction.

DF won't let me build a 3x3 up stair in the space; it says it's blocked. However, it does let me build a 2x3 stair and a 1x3 stair to fill the same space. Why?

z+1 is the level above the build issue where the last up/down stair (designation) is.. z is where the 2 up-stair constructions are (2x3 on top, 1x3 is the row on the bottom) and z-1 is cavern.

z+1      z       z-1
-----    --££-   .--  
-XXX%    £<<<%   -----
%XXX%    £<<<%   ,,',-
%XXX%    £<<<%   '𝓇-'-
%%%%%    ☼☼☼%%   ---.`
  • Mind providing some pictures of what you've got? Hard to know what we're dealing with without knowing what's on the 3 z-levels (level in question and +/- 1) – Raven Dreamer Dec 29 '13 at 20:19
  • Sure, as best I can. I can't figure out how to get an RTF dump of the map, so I've got to approximate with what I can type in. – mpounsett Dec 29 '13 at 20:50

After consulting your diagrams, it seems that you are building all of the staircases you want/need to, you just couldn't build them in a batch, correct?

If that's the case, then there are a few one-off issues that could have caused this -- trying to order the construction while the previous structures are still there; transient issues with claimed building materials being or not-being in the appropriate square.

In short; I'd not worry about it, as I don't think this is a common scenario to run into.

  • 1
    That's right. I was able to build a 2x3 and a 1x3, but not a 3x3; the 3x3 was marked as blocked. I couldn't figure out what was supposedly blocking it. – mpounsett Dec 29 '13 at 21:15
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    @mpounsett I think you need one accessible tile outside of any combined construction job - it acts like the mass of staircases is one building while placing it. – Brilliand May 16 '14 at 21:16

I would advise that you just build floors! A dwarf will end up stuck at the bottom but if you add another 1x1 up stair with a down stair above he will get back out of there. Replaing the Up/Downs with just Ups will stop walking creatures from coming in, but flying ones will go straight up!

  • You can't build floors without stairs in place because then there are no materials available (no way to carry them down). Leaving a single stair lets the materials down, but then that square isn't blocked against flying creatures. And it looks like you can't build a stair on top of a floor because the space is blocked. – mpounsett Dec 29 '13 at 21:14
  • That's why I said a guy would be left down there. You floor off the outside 8 stairs - the guy who floors off the final one gets stuck. Getting materials there in the first place is a non issue - if you've just dug the stairs, there will be stone lying around, if not, use a stockpile. Better than leaving the stairs open to flying invaders – Josh W Dec 29 '13 at 21:21
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    Up Stairs include a floor, so they're perfectly valid for blocking things off from below. – Raven Dreamer Dec 29 '13 at 22:33

I believe the issue is with carving/designating vs building/constructing. Since you already designated, or carved out the floor to make a up/down stairs you cannot designate/carve out a upstairs on that tile.

One of your options are to remove the stairs completely, then place a floor or up stairs through the build/construct command "b"-"C". If you do not have access then you need not designate another stairs next to your original 3x3 staircase to get there.

I always looked at a tile like this: It has a floor section and a block section. A up stair would have the floor in tact and a staircase in the block section. A downstairs is basically just a tile without a floor so it can reach the staircase below it. A up/down stairs have both a staircase and a hole in the floor.

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