Monday, September 16, 2019

Castle Construction Times

Chateau Gaillard
Previously I looked at some real-world data for medieval castle construction costs and found, somewhat surprisingly, that if we read the costs from OD&D in silver pieces (groats; 1/3 shilling) that they're quite close to the actual prices involved. I'm still jazzed at how sweet that was!

But one thing I couldn't figure out at the time was a way to estimate castle construction times. The real-world data was all over the map and not consistent; a small single keep at Peveril could take 2 years; medium to large castles like Orford or Dover took 8 or 10 years; and then on the upper end the "vast" castle of Gaillard which cost twice as much as Dover (and on a difficult-to-reach precipice) itself took only a lightning-fast 2 years. So I left that puzzle for a later day.

Well, that day is today. The players in my ongoing campaign are advancing in experience and treasure enough that they're starting to ask about options for castle-construction. The night of this writing I sat down and played with some numbers and discovered a remarkably simple rule that gives fairly realistic results. Here it is:

The base time for construction is the square root of the OD&D total cost, read in weeks. If speedier construction is desired: Each multiplied cost factor divides time by a like amount, up to quadruple cost/speed.

Let's compare that to the real-world data; it's a small sample size, but for game-design purposes I'm comfortable making a decision on this basis. Gray and yellow highlights are things added to the spreadsheet since last time. The bottom row for Gaillard is special, because it's the only one where we're applying our quadruple speed-up rule.

Castle Construction Time Estimates

In the 8th column, we have our squart-root estimate for time in weeks. For example, with the top row of Peveril, we take the square root of the D&D cost (identical to real cost in this case): sqrt(12,000) = 110, rounded to nearest whole number. Dividing that by 52 weeks in the year comes out almost exactly to 2 years, exactly the real-world time it took to build it (in the 4th column). Doing that for Orford and Dover likewise comes out within 1 or 2 years of the actual figures.

Now let's look at the last case of Chateau Gaillard. Just looking at a map of the place, it looks smaller than Dover Castle (compare "Details" in the 5th column). My estimate using the OD&D tables it that it should cost about 208,000 sp or so; and construction time ought to be sqrt(208,000)/52 = 456/52 = 8.8 years or so. But to this we will apply a speed-up factor of 4, quadrupling both price and speed of construction; then the price jumps to 832,000 sp and the time drops to 2.2 years. Note that these figures now align with the real-world prices: Gaillard cost some 720,000 groats (i.e., 12,000 pounds) and did indeed get built in just 2 years time.

Consider: Gaillard was the major work of Richard the Lionheart, who worked feverishly to stake the world's finest castle directly in the heart of his French enemies. He personally supervised the work and drove laborers unrelentingly, even through reported rains of blood. Said one observer: 

... the king was not moved by this to slacken one whit the pace of work, in which he took such keen pleasure that, unless I am mistaken, even if an angel had descended from heaven to urge its abandonment he would have been roundly cursed.

Note also at least one nifty side-effect of our square root rule: Designing a large castle up front will take overall less time than if you build a small construction and add to it over time. Say, two separate rounds of 10K construction would take sqrt(10K) * 2 = 100 * 2 = 200 weeks. But one round of 20K value construction would be just sqrt(20K) = 141 weeks. This sort of jives with the classic engineering experience that it's more efficient to get a design right early rather than late; and provides a neat in-game dilemma on whether a PC should get started with something small with available resources, or wait to gain more treasure so as to start on a larger (and ultimately faster) construction.

(N.B.: There's a bolt from the blue waiting for the first person who suggests Agile castle construction methodology.)


25 comments:

  1. Split your stories. What is the smallest piece of a castle that has value to the user?

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  2. The gamist in me says, “let the castle be finished in one calendar year.” This is what I will do when my first player builds a castle.

    But as usual your application of real world data and smart maths makes so much sense from a simulationist standpoint.

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    1. I think sometimes in these case (particularly big-ticket campaign items) letting the facts of reality lead me in a place I wouldn't have made up on my own provides freshness and productive struggle.

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  3. "If speedier construction is desired: Each multiplied cost factor divides time by a like amount, up to quadruple cost/speed."

    Well, Dwarves, Profit Minded Stone Giants, and binding earth elementals ain't gonna come cheap.

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    1. Oh wow, nice. Now I'm fantasizing about different pros/cons to pursue for each of those. :-)

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  4. The things to keep in mind that castles were fantastically expensive especially considering they were not productive in of themselves.

    So it likely the widely variable construction times doesn't represent the true time but rather that the builder spaced out their outlays over a period of time to match what they had in revenue.

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  5. What Robert says. Also, my understanding is that (at least in northern Europe) construction pretty much stopped during winter (because e.g. mortar wouldn't set, ground too hard, etc). So probably productivity is higher in summer, standard in spring/fall (maybe lower than expected because of planting & harvest requirements), and very low in winter.

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    1. I'd like to see a citation for that. Related: I'd gotten the impression that in that same area, travel basically stopped in the winter. But when I pursued the academic literature on that, the data shows pretty strongly it was a myth.

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  6. I can't recall where I read this, but my understanding has been that medieval peasants owed a certain numbers of days of free labor to their lords - in pre-Black Plague Europe, anyway, peasants in general had greater bargaining power due to the labor shortage and began to wrest better terms from their landlords starting in the 14th century. But I digress. Point being, to the best of my knowledge most castles would be built using this free labor, keeping costs down but limiting its speed based on the number of days' labor that a lord's peasants collectively owed. Whereas for Chateau Gaillard, King Richard was presumably using hired laborers since it wasn't in England, so the cost skyrocketed, but it also meant that he could have construction progressing continuously for 6 to 8 months out of the year instead of only 1 or 2.

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    1. I'll wager that some/many of those peasants also saw the castle's construction as benefiting them with protection down the road. But most peasants probably weren't highly trained craftsmen. So, lots of 'dumb' labor for clearing land, digging moats and foundations, and filling walls with rubble. But the finished stonework and carpentry are going to be expensive and time consuming.

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    2. The word you're looking for is corveƩ. Peasants would be required to work approximately one day out of every 12 on public works, or about 30 days a year.

      It sounds like a lot but peasants actually didn't work a lot of days in the fields - something like seven months.

      It was the exception rather than the rue for a peasant to labor on the lord's private property but undoubtedly it happened. More frequently it was to maintain public works such as roads and ditches.

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    3. Sure, I never said that it was excessive or coerced, just that it was owed. The most detailed estimates I've read are that medieval commoners worked between 240 and 250 days out of the year, which is actually pretty close to what you work at a modern Monday-Friday job, just the work days are distributed differently across the calendar. And for sure some experts were needed in addition to peasant labor, which is why even the (relatively) cheaper castles were still expensive. But actually, the daily rates for carpenters and masons weren't that much higher than for unskilled laborers. When labor was plentiful and cheap, a carpenter might make double what a laborer did, and a mason 2.5 to 3 times as much. However, at times when the labor supply was lower, such as post-plague, the rates might be something along the lines of 4 pence per day for a laborer, 5 pence per day for a carpenter, and 6 pence per day for a mason.

      Point being, just needing to hire any kind of worker using actual money, instead of receiving labor as a type of rent payment, was expensive no matter what - and it sounds to me like King Richard was probably relying exclusively upon hired hands for Gaillard.

      Also agreed that a peasant's labor was usually allocated to more mundane works like roads; castles lasted centuries. As a ballpark figure just from ones that I've anecdotally looked into, a smaller 12th-century castle might be expanded/improved somewhere around the 15th century, and by that time the peasants were almost certainly paying their rents in coin rather than in goods and services. Between 2 and 10 years spent castle-building out of 300 or more is quite a small percentage.

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    4. It's something that I definitely wrestle with from time to time in regards to issues like this, early knights-service versus later scutage, levies vs. standing army, etc. There are times that I want to model all of those systems that feed into support of medieval armies.

      But the truth of it for our D&D games that practically all of us play PCs as showing up with no land or fiefs and big sacks of coins instead. So it makes for a pretty crisp simplification to assume some kind of late-era economy with everything based on cash payments. Gives us a thinner system and interfaces with our PCs better in that regard.

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    5. That's fair to just assume all labor will be hired; my real point was conjecturing that much of the true cost of those first three castles was obfuscated by non-hired labor. And that Castle Gaillard might have cost nearly the same amount of money to build whether it was built in 2 years or 10 years.

      My hypothesis is that for "cheap" castles that leaned heavily on peasants' manorial labor obligations, construction time was largely a factor of that labor supply. Meanwhile, for castles relying on hired laborers it would be a matter of financial throughput rather than absolute cost - if you could only afford to devote £2000 per year to building, then a castle equivalent to Gaillard would take 6 years to complete.

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  7. Slower or no construction cold climes during winter, but also slower or no construction in warm climes during summer.

    I know many departments of transportation reschedule roadwork during the summer for overnights (probably not an option for castles) or pass altogether. There are other summer weather factors too - hurricanes and just summer thunderstorms. So at the extreme northern/southern limits I'd bet that there's an equal amount of time lost to weather/climate.

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    1. I don't think that summer slowdown would hold in Europe. Hurricanes are few and far between there, and when they do get something one it's nowhere near as bad as what hits the US South. As for thunderstorms, the warmer parts of Europe are along the Mediterranean, and have a reputation for very dry summers. As for the DOT scheduling construction at night, that's primarily due to the fact that there's less traffic as night, so they can work on three lanes out of a four-lane highway without causing a 20-mile traffic jam. They're out during the day if it's only a one-lane job.

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    2. Admittedly for me I might say that those two characteristics mostly cancel each other out. Maybe. :-)

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  8. I prefer the waterfall method of castle construction, where a castle is built on a suitably scenic waterfall.

    (Your math more-or-less lines up with my math: https://coinsandscrolls.blogspot.com/2017/09/osr-building-castles.html)

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    1. Why, I oughta... oh, actually that's an extremely pleasant idea.

      And a very nice system on your blog, thanks for sharing that!

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  9. I'm assuming you take the square root of the cost because you're dealing with square footage... so if you were building a wall instead of a castle, you'd be dividing the cost instead. Although I'm thinking you could work out a standard unit of square footage that would make sense in the game and just multiply the number of areas you are building in by the base time.

    I would probably have to go that route, since I came up with an idea of estimating costs by using the cost of a ship as the base cost and asking "how many people are going to be housed in the structure?" and adjusting the cost accordingly... then doubling or tripling the cost because it's stone rather than wood. But I never got to the point where any players actually needed to build anything, so I never worked out building times, anyways.

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    1. Actually, no, it's just a simple mathematical model that seems to match the real-world time data pretty well.

      Or in other words: Perhaps more research needed for why that's the case.

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  10. To add to my previous conjectures that, if the PCs are paying entirely in coin and don't have any feudal peasants contributing labor, that something on the order of 3 to 4 times the OD&D price might me needed:

    From the UC Davis Medieval Price List web archive (http://medieval.ucdavis.edu/120D/Money.html) there is a section about Langeais, a rectangular, tapering stone tower built in 992-
    994. The dimensions at the base were 17.5
    meters by 10 meters; the height was 16m - so about equivalent to the Peveril Castle tower.

    Labor Costs, in Average Working Days (AWD):
    procurement: 14 250
    transport: 2 880
    labor:
    unskilled: 63 500
    mason: 12 700
    smith: 1 600

    Later in the list, they give pay for a laborer circa 1300 as "£2/year max," which would translate to 2d/day. Rolling the year back to 992, let's assume half the pay, or 1d/day for simplicity. The mason and smith might earn 2d/day, and I'm unsure on the procurement and transportation costs, but I've read accounts qualitatively claiming that it was costly to transport goods in the medieval period, so let's say those are at least twice as expensive as unskilled labor as well.

    We end up with labor costs in the ballpark of 120,000d = 10,000s = £500. That doesn't even count the cost of any materials that the lord was unable to extract from his own lands and had to pay for. So adding in an unknown amount extra for material costs, it's looking like at least triple the £200 for Peveril, and over 100 years earlier as well so possibly some inflation occurred during that time, perhaps making the inflation-adjusted cost of Langeais in 12th-century pounds closer to £800 - or 48,000 coins in your 1 groat = 1 silver piece system.

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    1. That's great data, I'll have to think about that. Thanks so much for pointing that out!

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