Are there any rules for building settlements from the ground up?

Question

I am running a game set in a destroyed city (in a destroyed world), almost every building has been flattened to its foundations or reduced to just a few standing stones.

Are there any published rules; or homebrew rules that you can back up with experience, that cover how long it might take to reestablish the town as a functioning settlement; including rebuilding, setting up farms etc?

I am aware there are costs associated with buildings in the DMG, but I am not looking for the players to run the town, or finance it. I just want to ensure it grows in an organic manner as the populace put their efforts into rebuilding.

Bonus points if someone has a set of rules which include finding enough food for the townsfolk, setbacks and any other sensible flourishes.

Answer 1

They’re in Acquisitions Incorporated.

The semi-official book Acquisitions Incorporated, written by Penny Arcade and published by Wizards of the Coast, includes rules on PC parties building and expanding bases of operations for the group, as well as managing NPC minions to run and maintain said bases.

Some of the example bases for PCs include things like abandoned lighthouses or ruined mansions, so a flattened town would likely also work - maybe they’d start off camping in the sewer system or an intact basement.

Answer 2

5.0 does not contain any mechanics for economic growth or large-scale repairing.

The DMG has a section called "Building a Stronghold" which contains gold costs for various structures (p128 in my version). This attributes gold costs for various structures. You can determine the cost of the full structure, translate the damage done to a town to gold cost per building, and use these tables to assist in calculating reconstruction effort. Most of those put a value on the size of the structure, the cost of the raw materials needed to build it, and the manpower required to construct it. So, a farm would be much cheaper and quicker to create than a fort although the farm is unlisted.

These efforts can be modified by spellcasters. Smaller repairs can be done using the Mending spell, while larger might be done with Fabricate. This would greatly reduce the time needed for reconstruction.

Mending

1 minute cast time, 2 lodestones as materials

This spell repairs a single break or tear in an object you touch, such as a broken chain link, two halves of a broken key, a torn cloak, or a leaking wineskin. As long as the break or tear is no larger than 1 foot in any dimension, you mend it, leaving no trace of the former damage.

This spell can physically repair a magic item or construct, but the spell can't restore magic to such an object.

Fabrication

10 minute cast time, consume raw material as per below effect

You convert raw materials into products of the same material. For example, you can fabricate a wooden bridge from a clump of trees, a rope from a patch of hemp, and clothes from flax or wool.

Choose raw materials that you can see within range. You can fabricate a Large or smaller object (contained within a 10-foot cube, or eight connected 5-foot cubes), given a sufficient quantity of raw material. If you are working with metal, stone, or another mineral substance, however, the fabricated object can be no larger than Medium (contained within a single 5-foot cube). The quality of objects made by the spell is commensurate with the quality of the raw materials.

Creatures or magic items can't be created or transmuted by this spell. You also can't use it to create items that ordinarily require a high degree of craftsmanship, such as jewelry, weapons, glass, or armor, unless you have proficiency with the type of artisan's tools used to craft such objects.

Player characters with high strength stats would also be able to help rebuild much faster by moving the raw components where they need to go, and helping craft the necessary components to aid in reconstruction.

These are ways for you to create a plan for reconstruction and how to expedite it if the characters wish to contribute their time and effort.

Answer 3

There are currently no published rules for this

It's hard to prove a negative, and this answer may become outdated if a book on this will eventually be published, but as of this posting, there are no detailed offical rules on the economics for growing or building up a settlement. The focus of the game is clearly on the small adventuring party, and much less on estate management than earlier editions.

If your setting is a "destroyed city in a destroyed world", the availability of resources and knowledge may be quite different than what the game assumes as the default setting in the Forgotten Realms, so even if something gets eventually published, it might not be a good fit.

There are general rules about designing settlements in the DMG on page 15 and following. Designing and growing settlements is done by DM fiat, narratively. You can decide it the city prospers and grows, based on the adventures and actions of the PCs (they defeat the raiders, secure the water supply from the dragon etc.), and just describe it.

If you want to turn it into a mini-game for your players, you would need to come up with your own or use third party rules. It might be useful to look at the Dark Sun setting for an example of a destroyed world. Or you could look at earlier editions of the game, like OD&D which has flexible rules on keep building, hiring specialists and running "Baronies" in Volume III: The Underworld and Wilderness Adventures, p. 20-25; or AD&D first edition DMG, which has more in-depth sections on hirelings and construction that translate quite well to 5e. If you want to convert the prices into 5e, based on all the equipment in 1e that also appears in 5e, 1 gp in 1e has about 26% more value than one in 5e. I think it is close enough so you can just use the prices as is.

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P.S. I also find the free A Magical Medieval Society: City Guide well written for thinking about fantasy cities in general, but it would be more useful for a bustling, not a ruined city, and does not contain detailed economics to build a settlement from scratch, either.