I have been looking into kingdom building rules for the sake of my newest game and I noticed that a lot of buildings have prices like 42 BP or 38 BP and that made me think that they were somehow made using a set of rules similar to how buildings are made using rooms as a basis. So what I want to ask is that are there any rules for designing custom kingdom buildings based on their effects and how many lots they occupy?
Are there rules for designing custom buildings for kingdom
content-identificationpathfinder-1erealm-management
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Birthright is a larger scale system designed for interaction between multiple mature countries. The AD&D 2nd Edition campaign setting is set in the world of Aebrynis on the continent of Cerilia which is ~very~ detailed at the ruling level. The setting has divine magical "bloodlines" from the old (dead) gods that allow the regents to rule Law, Guild, Temple, Source and Province/Land Holdings as a core concept. Domain development is done in turns, a turn is a season of three months and the regent gets one Domain Action per month. You can construct some general high level holdings, conduct trade and war, etc. but the building is abstracted into Holdings. E.g. Increasing a Temple Holding from level 1 to 2 in a province may involve upgrading your existing chapel, or building another one in a neighbouring village, or it may just result in more worshippers at existing structures.
A fully 3.5e'd version of Birthright has been created by the community at birthright.net. These rules are meant to be the primary focus of a campaign with "adventurer level" action as a sideline. So much so that there is a Domain Action specifically for it called "Adventure".
Kingmaker is mostly a specific adventure path with some specific rules about carving a new civilization out of largely-unsettled areas and being sustainable. It has a more micro focus - exploration and then construction down to the building level ("I build an inn this turn!") Also keep in mind these are supplemental rules in an AP; there's 9 pages of kingdom building rules, then more later on mass combat and exploration, but the core is small. The rules have been reprinted in Ultimate Campaign, but not in significantly more detail. They are suitable for settlement building as an adjunct to a normal campaign.
Sorry, it took me a bit to finish reading Ultimate Campaign. All right, a comparison of the kingdom building rules in "Of Cities and Kings" from Rivers Run Red, the second issue of the Kingmaker Pathfinder Adventure Path, and the kingdom building rules from the Pathfinder RPG hardback Ultimate Campaign.
They are basically the same rules, slightly expanded. What is 10 pages in Rivers Run Read is 30 pages in Ultimate Campaign, plus some pages of optional rules.
Some of that is more options - like in terms of Leadership Roles, Rivers Run Red has 11 and Ultimate Campaign has 14 - and some of it is padding; for example the Councilor entry has the same mechanics but 6 lines of fluff verbiage rather than 1. So that additional page count is part more stuffs and part blabbering (though if you were confused by the sparsity of explanation in the Kingmaker version, that's not necessarily bad).
The "Improvement" phase gets renamed the "Edict" phase and other such, but in general you're getting the same system with a bit more of each of the lists-of-bits. There are some more buildings; you can do terrain improvements (waterways, bridges)... What it doesn't appear to have a bit more of is playtesting. Same system, most of the same holes. They did do bolt-on fixes to plug some of the most well known holes, like in the Income phase you can no longer sell magic items created by your city (no real in-game reason given, just to stop the "infinite monies exploit" popular among Kingmakers). They also took the Economy +1 and left only the Loyalty +1 benefit on graveyards, to avoid the Necropolis Gambit. So the various costs and DCs are left 90% the same, with some tweaks.
In general you are getting the exact same system in Ultimate Campaign (same grid layout page, same mechanics) with some additions and some cursory changes to prevent the most well known of the exploits in the previous system.
Best Answer
No (and there's only a little bit of guidance)
There are no rules from Paizo for custom buildings. There is some guidance on what drives BP prices, but it's not enough to constitute rules for custom buildings:
(source: Ultimate Campaign)
(source: Ultimate Campaign)
The closest you can get to deriving rules for custom buildings is to try to reverse-engineer the existing building prices, but that actually points to there not being a specific formula for it: this post and this post from the Paizo forums by bmcdaniel finds that there's no deterministic way to derive BP from the inputs. If Paizo used a formula, they massaged the results in a way that they have not defined in the rules, so any custom building will inherently be homebrew.