Building a castle: The mundane way

I was reading Hermetic Projects and think "the rate the Great Tower is build is pretty OP no?". Maybe my conversion is wrong (because I play the game in spanish). But my investigation is that four floors 80 feet tall in total and 2.000 in diameter is bigger than any castle that exist in earth, and you do that in ONE year with a profesional mason. In fact, in one season you can construct 2.000 diameter 20 feet tall floor, that's crazy.

I really don't like this, more because I like my sagas slow and steady. My players wants to build a castle and, in fact, they want to do it by parts and necesity (two floors as base, and new floors being added as needed), and I don't know how to say to them "you can build the entire castle in one seaon."

So, I come here for some more reasonable advice in construction speed. Don't be shy with calculations, I really like the 5 Craft calculations for products, but the construction ones are a little vague for me (a castle in five seasons sounds good, what don't sounds good is what is the size of that castle? How many floors and square meters it has?)

Thanks for reading <3

I think you miss a critical sentence

This chapter assumes that
a sufficient workforce can be retained and
enough materials obtained to keep the
building work going in perpetuity. [HP:36]

Yes, you only need one master mason to manage the works, but you need a huge force of labourers. Comparable historical works used slavery (to the extent that they exist at all). I would consider it very unlikely that the characters can pull this off, except in border areas with populous neighbours where they can take slaves in bulk.

I agree that 2000' diameter is enormous, and feels ridiculous, but we are talking about the Tower of Babel. It will need such a broad base to build into Heaven ...

I know that too, is the reason I want to know how much 20 feet tall square feets is the average of construction in Mythic Europe for a more general speed construction.

Instead the "a tower is 2 seasons and a castle is 5", I want a "mason with Craft 5 and 10 laborers can build 60 square feet of 20 feet tall in one season"

I sometimes use this medieval price list when considering medieval prices.
It quotes:
The following are the estimates of raw materials and labor that went into the tower of Langeais, a rectangular, tapering stone tower built in 992-994. The source is [6], pp. 47ff. The dimensions at the base were 17.5 meters by 10 meters; the height was 16m (3 floors); the walls were 1.5m thick, made of two shells filled with loose rock.
Limestone in building: about 1050 cubic meters, or 2 600 000 kg
Wood in building: 47.5 cubic meters, or 34 600 kg
Nails: 3 400, or 50 kg
Mortar: 350 cubic meters.
To make the mortar:
sand: 225 cubic meters, or 360 000 kg
limestone: 40 cubic meters, or 160 000 kg
green wood: 540 cubic meters, or 286 000 kg
Labor Costs, in Average Working Days (AWD):
procurement: 14 250
transport: 2 880
unskilled: 63 500
mason: 12 700
smith: 1 600
[6] "The Cost of Castle Building: The Case of the Tower at Langeais," Bernard Bachrach, in The Medieval Castle: Romance and Reality , ed. Kathryn Reyerson and Faye Powe, Kendall/Hunt, Dubuque, Iowa, 1984

So, the cost for Fulk III of Anjou to build a decent stone tower over 3 years includes a vast amount of labour, a lot of which will have to be scheduled around the agricultural year (as the unskilled labour will be needed for preparing the land for sowing in spring, and harvest uses every scrap of labour available.)

In the late 13th century, Caernafon castle cost £25,000 over 47 years from 1283-1330, so £500/year represents quite a lot of labour.


Oh, that's a classic. I have not seen it posted for more than twenty years.
It is really solid work.

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Realistically it will depend on a thousand factors you don't want to consider- type and availability of stone being a key one, how much effort is being put into safety, for a really large/long project you may even be training your workmen at the and as apprentices at the beginning. How much security is required and how much that may delay building (also depending on the type of security- holding off wildlife and raids is very different from preventing spies from infiltrating construction)

This is interesting, as it suggests that you'd need 5 unskilled workers (probably mason's apprentices) working full time with 1 mason, and that the mason would take up roughly 1/8th of a blacksmith's time (presumably in chisel sharpening and/or making new chisels).

Since it was done over 3 years there was probably at least two masons involved, as there's only so much time in the day and weather and holidays limits available working time. I could easily see it being broken up into 3-5 masons, what with potential illnesses/injuries and whatnot.

So it could be as much as 5 masons and 25 'helpers' over 3 years to build one tower.

If you work the numbers quoted, you have at least 100 people involved at a time, on average ... probably more, both because there were a lot of feast days, and because the work would be concentrated off-season.

I was focusing more on the mason side of things because the skilled labor is the highly limiting factor (each mason can only dress so many stone blocks a day, regardless of how many blocks you can bring them). Explains why they used rubble fill wherever they could, a much quicker/cheaper way to fill volume once you've got the external dressed stone in place.

For a modern analysis of what it would take to build a castle I would suggest taking a look at Guedelon (

This project gives a good insight into what levels of labor are involved. The website says that they are 40 people and they have been going for at least 10ish years now. However it is not clear to me how many hours each person works. I would suggest sending them a message to get a feel for the amount man-hours put into the effort.


I know this is about mundane castle building, but its also worth noting that even quite low level magic can MASSIVELY speed up the process of building.

Simple things like digging out pits for foundations, digging moats, creating perfectly square stone blocks ex nihilo, even incredible basic magic items like a glove that lets you carry stone blocks easily, or a chisel that can swiftly cut stone, can hugely speed up what are otherwise extremely time and staff intensive activities. And they can generally be done by very low level magi too.


for this purpose my personal favorite is any items that casts any version of Rock of viscid clay. The ability to turn stone temporarily into clay and be able to mold it and have it revert to being hard is super useful.

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We should keep in mind that even without magic, people in our own history already were employing lots of time/cost saving techniques that should significantly influence estimates on construction. The recycled spolia in what would be the Theban Tribunal comes to mind. From Saradi's The use of ancient spolia in Byzantine monuments: The archaeological and literary evidence -

Convenience was certainly a determining factor in recycling earlier building material. This is the impression we gain from several imperial decrees. A passage of St. Gregory of Nyssa referring to the erection of a martyrium at Nyssa seems to allude to the same reason: since it was time-consuming to cut the stones in the appropriate manner, clay bricks would be used to fit in with stones that could be found around. Thus time would not be wasted in adjusting the surface of the stones with one another..

And this practice, with so many others from the Byzantine Empire, was cheerfully adopted and further developed by the Rum Seljuks during the 1200s - developed so far in fact that it led to an unprecedented boom in stone construction which included the most extensive single decade of new completed stoneworks in the history of medieval Asia Minor. From Redford's City Building in Seljuk Rum: 1210-1230 -

In medieval Anatolia, building meant rebuilding, recasting and recycling. The Seljuqs of Rum may have learned architectural recycling from the Byzantines, who had long plundered the stone blocks of buildings from earlier eras for the stuff, and ornament, of their buildings. The quantity of building undertaken by the Rum Seljuqs during this period is unthinkable without this thrifty building principle in mind.

Like the Rumis prove, even non-magical construction circa 1220 can happen quite "fast" in some respects with the right conditions and clever planning.