v0.34:Bridge

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v50.12 · v0.47 · v0.34.11 · v0.31 · v0.28 · v0.23 This article is about an older version of DF. More Info · V

Bridges are extremely useful buildings for crossing dangerous terrain and also for fortress defense. Using them to control fluids can save a ton of mechanisms and time, especially when the fluid in question is free-flowing and not pressurized (by pump, river or hydrostatic anything) and needs a wide tunnel.

Building Bridges

Bridges can be built (b -> g) of metal, stone or wood. They are first designed by an architect, then require a specialist worker for the material used (e.g. a mason for a stone bridge). The size of the bridge can be altered with umkh while placing it, up to a maximum size of 10 squares in each direction. The bridge must be anchored to a solid surface on at least one edge. Before placing the bridge ensure that the bridge raises in the direction you want it to using wadx or retracts using s. The direction points to the side of the bridge which will become a wall when the bridge is raised.

Materials: When choosing materials, the order that they are presented on the list determines how the bridge will be labeled, NOT WHAT ORDER YOU PICK THE MATERIALS! The highest one up on the list is the core construction material. This will define the color of the bridge (and possibly how fire resistant it is, although this hasn't been tested extensively). Materials are placed on the list in order of distance, so simply make sure the primary material is the closest or at least closer than any secondary materials you wish to use. You will need the number of tiles divided by four plus one ( Tiles/4+1 ) of material to build the bridge.

Dragonfire is so hot that it can destroy bridges made of almost any material, but a bridge made of adamantine can sustain dragonfire for extended periods of time before it melts.

Big bridges can take weeks or even months to complete. You can shorten construction time by moving the materials to the site before starting construction, and by using blocks instead of rocks. The material-gathering time is somewhat shorter for blocks due to their lesser weight, and the actual construction is three times faster for blocks.

Raising and Retracting Bridges

All bridges in DF can be raised or retracted by linking it to a lever. This requires a mechanic's workshop and a dwarf with the mechanics labor activated.

If a bridge is set to retract when the lever is pulled, the bridge essentially disappears dropping anything (friend, foe, or object) on the bridge onto whatever is underneath. Clearly this can be used to drop your enemies to rocky/watery/fiery deaths (or anything more imaginative you can think up!).

If a bridge is set to raise when the lever is pulled, the bridge becomes a wall along the edge selected with the wadx keys when placing the bridge. The resulting wall is always one z-level tall, regardless of the length of the bridge. The wall acts as if it was constructed, rendering it invulnerable to building destroyers and also watertight. ^[Verify] The bridge also "moves" to this position very fast, firing anything on the bridge into the air. The key advantage to raising bridges is the creation of a wall when the bridge is raised. This can be used to block fortress entrances/corridors. Using 2 bridges at opposite ends of a corridor creates a very large and simple trap by walling in enemies. Or... Smashing them to tiny bits if placed to raise facing each other, with no space in between. For added effect, place pressure plates on both ends to raise the bridge when stepped on, to fling the units. If there is a floor directly above, they will be stunned. If there is a floor beneath the bridge, and if nobody is on the pressure plate, they have to be lucky to not be smashed on the floor when the bridges come down. If there is no floor beneath the bridge, they will fall, sometimes into something very, very bad.

Walls cannot be built along map edges. Because bridges can be built along map edges and then raised to act as walls, they can be used to control where enemies spawn on the map.

If you aren't sure whether or not a 1 tile thick bridge is raised or lowered, try to build a piece of furniture, like a bed, on it. If it says blocked, the bridge is raised, if it says building present, it is lowered.

The lowering of a drawbridge can also be used as a waste disposal for unwanted stones, refuse, goblins (dead or alive), legendary cheese makers and nobles, to name a few. Even fluids get destroyed (this is especially useful considering lack of chasms in the new version). However, lowering a drawbridge onto a sufficiently large creature (such as a forgotten beast) simply destroys the bridge.

Notes

Bridges will not operate if any one creature of size 1200000 is on them. This weight limit is not cumulative - a bridge will still retract if a hundred goblins are standing on it, but a single rutherer accompanying those goblins will prevent the bridge from operating. Attempting to lower a drawbridge onto such a creature (in order to atom-smash it) will cause the bridge itself to deconstruct.

It is impossible to channel out stone that is directly under a raiseable bridge when it is in the raised position. Likewise digging a ramp under a raised bridge will not remove the floor tile.

Non-magma-safe bridges will heat up and eventually melt if the center tiles get covered in magma or exposed to dragon fire, whether the bridge is raised, lowered, or even retracted.

While bridges do not provide structural support, the game will still allow you to place unsupported constructions adjacent to them which will result in an immediate cave-in once completed, often tossing the unlucky mason off the edge to a horrible death. However, extending a supported construction alongside a bridge will not cause a cave-in.
Example:

Will cause a cave-in	Will not cause a cave-in	Key
B B B . B B B X B B B . F F F W	B B B . B B B X B B B W F F F W	B Bridge F Floor tile W Existing wall X Wall to be constructed

Destroying bridges can be hazardous, as dwarves are not as compunctuous as with constructions and diggings to make sure no one is standing on them before destroying them.

A raised bridge cannot be linked to a lever from the inside - the mechanic must be able to stand in the center of the bridge.

Uses

Remote controlled gateways

Lever-controlled bridges are one of the safer ways to control access. They are immune to building destroyers, though care must be taken to avoid operating them in the presence of exceptionally large creatures. Magma safe material should be used in the construction if there is any chance magma might flow over the bridge.

Retracting bridges can be built covering the top of a ramp and can never be destroyed from beneath.

Floodgates

Raising bridges make a good replacement for most floodgate uses (e.g. flow and access control). They have the advantage of not being as easily jammed: they fling or atom smash all items and all but the largest enemies on their tile/s when they open or close, whereas a floodgate will jam open with a discarded sock in it. Further, bridges cannot be destroyed by building destroyers, while floodgates can be. A single bridge can also be made up to ten tiles wide, potentially replacing ten floodgates and saving many mechanisims and much work. One minor downside of bridges compared to floodgates is that bridges with a width of 1 look the same when raised as when lowered, so it is easy to confuse whether they are closed or not. If you are unsure of a bridge's status, check the control lever if there is one (in most tilesets, lever to the right means closed), or try to build furniture on top of the bridge and check the resulting warning message ("blocked" means the bridge is raised, "building present" means it's lowered).

Ocean drains

Dig out ramps leading up to the first level below an ocean. Build a retracting bridge on that level, directly over the ramps (be sure to leave them in place!) and link it to a trigger. Carefully seal off the chamber to make it water tight. Now with the bridge in place, designate ramps up to the ocean adjacent to the bridge. Diggers with access to the level below the bridge can dig those ramps up from the level of the bridge, allowing the ocean to fill the chamber; even with the ramp squares underwater they can still dig them out. And not a drop of water will touch them... provided they clear out before you pull the lever.

Caravan exits

A bridge to nowhere, built well above ground level at the edge of the map, can sometimes serve as a handy exit for caravans and diplomats when goblins harass. But sometimes it stops working, and I'm not sure why.

Cave-ins

Since bridges don't support adjoining rock, it is possible to set up a cave-in so that dust can't come up, dwarves can't fall down, and flying creatures can't come up from beneath the cave-in before you set it off.

Stops on the elevator

Designate a dumpsite or set up a floodgate at the top of a shaft; use multiple remote-controlled bridges to decide on which level the stuff, water, magma etc. gets off. (bonus: use water falling at one end of the bridge to flush stuff off that was dropped onto the other end without the manual labor)

Minecart routing

Minecarts can travel along unraised/unretracted bridges as if the bridge was a minecart track. This can let you change minecart routes via pulling levers.

Single Lever Airlock

Raising bridges and retracting bridges controlled by a single lever will be in opposite states of being open or closed. When one is closed (raised) the other is open (retracted) and vice versa. This fact can be used to construct airlocks that are not vulnerable to building destroyers or mistimed lever pulls e.g.

  Side View:
  Z1    XXXXXXR____      D = Raising drawbridge   / = Ramp   _ = Floor
  Z0    D_____/XXXX      R = Retracting bridge    X = Solid Rock or Constructed Wall

With a suitably long distance between the two bridges, the controlling lever can be placed within the airlock, and by setting the profile of the lever specific dwarves can be moved between isolated areas.

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