How much does a road cost? How about town walls?

Question

My campaign has just finished Hoard of the Dragon Queen, and the players want some downtime activities. I'd like to give them the option of renovating the Hunting Lodge they captured from Talis, and also help renew the quality of life in Parnast after long occupation by cultists.

So I'd like to give them a bunch of possible investments for their newfound fortune. Are there standard costs for roads of various types (dirt, clay, paving stones) in various environments (mountains, forest, swamp, etc)? What about town walls, defenses (wood, stone, guard towers)?

Answer 1

There's almost rules

Actually, not quite. There aren't rules for building or maintaining roads, and certainly not which makes considerations for environment. D&D 5e trusts this kind of adjustments for your (the DM's) good sense.

That said you have some guidance to base yourself on. The Building A Stronghold section in the Dungeon Master's Guide (p. 128) includes some costs and construction times for things like towers (fortified; 15,000 gp), keeps (50,000 gp), or forts (15,000 gp).

You might be able to find more detailed descriptions for older editions or on the web, but they might not translate properly. Your own judgement is trusted, and I would personally advice that you set the cost to be substantial relative to their wealth; but then make particularly good use of the Hunting Lodge/settlement in your campaign going forwards.

Answer 2

There's no specific table for "price to build a town" anywhere in official rules that I know of, but if you're trying to get an idea of the default value of money in the D&D world, be sure to understand the "Trade Goods Table" and the cost of "Services". So for instance, raw iron costs 1 sp per pound, and hiring workers to convert the raw iron into whatever you're trying to turn it into costs between 2 sp and 2 gp per worker per day, depending on the skill level of the worker.

Note that, of course, those are very generic and "default" valuations of things, and assume that one can readily find somebody selling the desired materials and people ready to work. It's quite possible, and even likely, that getting enough material to a place that doesn't already have it may be an adventure in and of itself (as who would want to escort the caravan of highly valuable building materials through the wilderness except a band of hardy adventurers). And of course, the local economy may not always have everything listed at the "book" price, particularly if there's suddenly a flood of resources coming into a region from the loot the party has brought with them.

I expect that for building roads in particular, a lot of the cost would be labor based (digging up dirt, using wheelbarrows or carts or the like to get it where it would go, and cutting down trees and bushes in the way, and so on) rather than materials based. So you may just need to make an educated guess about how quickly a road can be built in whatever environment using however many laborers, and if those laborers are available to do the work, then use that to come up with a cost.

And if that number doesn't seem to be right or make sense to you, make up a different one. The numbers in the book are all made-up anyway.

Answer 3

As stated in the comments, the asker is okay with roping in non-5E content, so let's look at some options.

Stronghold Builder's Guidebook

This is a third edition book that, as the name implies, is all about building strongholds. However, the rules are flexible enough that you can build basically anything with it (a couple auditoriums, some common areas, a few labs and workshops, barracks-as-dorms, and a number of offices makes for a pretty good university. A workshop with a bedroom above it could easily be a blacksmith's home/shop. And you can use the rules for building curtain walls to build walls around the town. The one thing it is missing is cost to build roads)

It also includes rules for modifying construction costs based on the environment you are building in, and has allowances for available natural resources being around to help reduce costs.

Something to keep in mind is that this book is extremely granular and will be having you pick out doors and locks individually for your rooms. Additionally, the construction prices in this book are pretty high.

Kingmaker

Kingmaker is from first-edition Pathfinder (which is mechanically very similar to D&D 3.5E), while it is technically an 'Adventure Path' it includes an incredibly robust kingdom-building and management system.

Unlike the Stronghold Builder's Guidebook, Kingmaker is much more high-level. Instead of building out your castle piece by piece, you just build "A Castle" and that is that. It has rules for laying out your towns, adding buildings to them, upgrading the connections between them, and so on. Then you eventually move on to claim more land and expand your territory.

Most of the rules are available on the Pathfinder SRD Website

Kingmaker abstracts the cost of building things into Build Points--however, there is a conversion of build points to gp,

1 BP is worth approximately 4,000 gp; use this value to get a sense of how costly various kingdom expenditures are.

and Kingmaker provides a table listing BP costs of roads in various terrain-types. So that can give you a baseline to work off of as well.

It is very important to note, however, that using the Kingmaker Rules fundamentally changes the game you are playing. These rules are very, very involved and tend to shift PCs from roving adventurers to being rulers working on a more political level.

My Suggestion

In your case, it doesn't sound like you really want to fully-absorb the Kingmaker Rules...but you want more civilian options than the Stronghold Builder's Guide gives so. So, my recommendation would be to look at the two rulesets and use them for inspiration to figure out how involved you want them to be in the town--and then use these things as a crude guide to get you pointed in the right direction for what it would take to repair/upgrade/etc all the things your players want to do.

Use them to get a rough ballpark of what things would cost, then go from there and mess with the numbers as suits your campaign.

Answer 4

Conversion from older editions

Other answers already pointed out that the 5e rules are very light on stronghold building and estate managment. It is mostly the "Building a Stronghold" prices for various buildings (DMG, p.128), the "Maintenance Costs" section (DMG, p. 127), and the overall equipment and price list for services (PHB, p. 159) with its cost for labor.

As you are OK to look at other sources, the 1e AD&D DMG has a flexible and rather comprehensive list of what various elements for building keeps cost, too (p. 107, Construction and Siege). 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.

By the way, there is an excellent investigation of real world castle construction costs on Delta's blog that concluded the values given in D&D 1e are pretty decent in matching up.