I’m currently designing a keep for my players to explore. It will be a ruined keep, taken over by an evil cult. But to start off the design, I am looking at how it would have been designed in its prime. Here are some rooms I’ve thought of when creating the layout.
Military function
- Armory
- Smithy
- Fletcher
- Training room
- Lookout posts
- Infirmary/Hospital wing
- Gatehouse
- Barbican
- Place of Arms
- Commander quarters
- Guard bunks
Every day operation
- Great hall (mess hall)
- Steward’s Office
- Clerks/Tax assessors/Scribes Office
- Kitchen
- Distillery
- Scullery
- Larder/Storeroom/Cellar/Ice House
- Servant quarters
- Bathroom
- Well/Cistern
- Dovecote
- Stables
- Kennels
- Courtyard
- Gardens
Political function
- Hall of Justice
- Dungeon/Prison/Oubliette/Tower
- Throne Room
- Vault/Treasury
Noble quarters
- Drawing Room
- Bower
- Rooms for the Lord/Lady
- Formal sitting room
- Informal sitting room
- Private study
- Personal library
- Private dining room
Research
- Library
- Alchemy lab
- Solarium
- Wizards quarters
Religious
- Temple/Church
- Clergy quarters
Can you think of some more?
Editing to add the suggestions from the comments.
Do not under estimate the size of the “every day operation section” and the “servant quarters”, Stuff like food or fire-wood isn’t delivered at the main-entrance but in some backdoor near the kitchen. You don’t want to see a servant carrying firewood or a bucket full of shit in the main hall-way, so you have “small corridor” for the staff.
Think about “How to feed that many people/animals”, and how to get rid of the wastes, and you’ve done on a long-way in your castle design. It’s also more interesting because suddenly, you don’t have a linear dungeon with a door and an exit, but tons of different way to access it.
I feel like I remember Matt Mercer saying something similar to this when talking about creating worlds, and then Brandon Sanderson said the same thing about his books, so I watched a few of his lectures to help with my world building.
A lot of what he does to make his worlds feel alive and real and expansive comes from putting himself in that world and thinking about what it would need to actually operate, then answer those questions with what’s available in that world. How do they feed themselves? Get water? Dispose of waste? Settle disputes? Travel when it’s too far to walk? Then you expand on those to answer what those things need.
They ride horses? Gonna need a stable and grooms and tack. Where do the grooms live? Who’s their boss and where does he go when not bossing around the grooms? Where does the tack come from? Made in house, gonna need a leatherworker and their own shop and place to live. Horses are also gonna need hay and to store it. Now you’ve got a farm and storage. A farm? Gonna need farmers. Where do they live? OP mentioned a wizard, so they have magic. Would they have used magic to make any of these jobs better/easier? Maybe the Wizard is upset about having to use his gifts to assist with lowly jobs and there’s some old note of him complaining? Now your players know to look for a wizard’s quarters from checking out the stables.
All of that just from them having horses. A little bit of follow-through can turn a boring map into a living world. It’s great.
I don’t know about that author, but definitely something that has been discussed on forums and paper magazines for decades. Even out of the RPG community, many castle visit are oriented across the various usage of the building through history. But it’s indeed a very great way to build stuff more interesting than a linear set of room, and even if you don’t care about “tactical fight” drawing a map that way helps understanding who is there and why (and is fun)
Which is another thing, many castles had various usage ans extension through history. They’ve been a military fort, then a prestige construction for some fancy lord, and finally became an administrative-center or a luxury hotel. Unless you want something big you don’t want to have all these functions at the same place. You can even get pretty small with the “fortified farm” that you often see across Europe, which is basically a large farm, but away from the safety of the village (more than 1h of walk) so which has it’s own walls to protect itself against potential criminal or a rogue army.