The Writer’s Guide to Castle Construction
If you’ve read my previous posts, The Writer’s Guide to Castles and The Writer’s Guide to Castle Defenses, you have probably realized that there were many types of castles throughout European history. As a result, the cost and time involved in castle construction varied widely.
If you are planning to have a castle under construction in your novel, I recommend you first decide on the type of castle, the location, and the budget of the builder.
As always, magic is the exception to the rules. Because magic.
Wood and earth were the cheapest materials for building castles. They were also plentiful and easy to transport. Most people did not need specialized training to work with them, meaning that a lord could call up his unskilled vassals and serfs to build his castle.
Stone was more expensive and harder to transport. It was also not as available as timber and earth. The blocks had to be cut out from a quarry then moved to the site. Some castles, such as Chinon, Château de Coucy, and Château Gaillard were constructed from stone quarried on the site. 
As a result of the high cost and difficulty of using stone, many castles throughout medieval Europe were made of a hybrid of the two.  It was also common for a country to have a mixture of timber, stone, and hybrid castles.
Another building material that is often forgotten is brick.  A brick castle is almost as strong as a stone one and there are castles that appeared to have been deliberately made of brick even when stone was available, such as Tattershall Castle in Lincolnshire, England.
It appears that both timber and stone (and possibly brick) castles were coated with a layer of plaster. This coating would protect them from the weather and make it difficult for attackers to know what they are up against. If you want to learn more, I recommend this video by Shadiversity.
Most of the surviving records of the cost of building castles are for royal castles, which were quite a bit more expensive than a country lord’s castle.  However, we do have some figures. For example, a small tower at Peveril Castle in Derbyshire, England would have cost around $137 USD. Château Gaillard in France, which was built between 1196 and 1198, cost between $20,600 and $27,500 USD. Much of the money went to paying for labor, especially skilled craftsmen, and materials. Master James of Saint George, who oversaw the construction of Beaumaris in Wales, explained it this way:
“In case you should wonder where so much money could go in a week, we would have you know that we have needed – and shall continue to need 400 masons, both cutters and layers, together with 2,000 less-skilled workmen, 100 carts, 60 wagons, and 30 boats bringing stone and sea coal; 200 quarrymen; 30 smiths; and carpenters for putting in the joists and floor boards and other necessary jobs. All this takes no account of the garrison … nor of purchases of material. Of which there will have to be a great quantity … The men’s pay has been and still is very much in arrears, and we are having the greatest difficulty in keeping them because they have simply nothing to live on.” 
The early castles could be constructed in a relatively short amount of time. It’s estimated an average-sized motte would have taken fifty people about 40 days to construct. However, it was common for stone castles to take a decade or more to complete. For example, Tattershall Castle took 20 years (1430 and 1450) and Beaumaris Castle was constructed between 1295 and 1330, 35 years. 
Timber and earth castles required only simple tools and techniques to build. However, more advanced techniques were needed as castles became more complex and stones was increasingly used. Scaffolding was employed and improved from it’s use by the Greeks and Romans.  The treadwheel crane was vital for raising and lowering large loads. I recommend this video of a reproduction treadwheel crane lifting a car.
Castles were not only expensive to build but also to maintain. Since the timber used in their construction was unseasoned, it often needed to be replaced. To give you an idea of the cost, Exeter and Gloucester Castles recorded repair cost of $27 and $68 USD annually in the 12th century. 
I hope this was helpful. Let me know if you have any questions or suggestions by using the Contact Me form on my website or writing a comment. I post every Friday and would be grateful if you would share my content.
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Copyright © 2021 Rebecca Shedd. All rights reserved.
 Erlande-Brandenburg, Alain (1995). The Cathedral Builders of the Middle Ages. Découvertes Gallimard ("New Horizons") series. London, UK: Thames & Hudson Ltd. ISBN 978-0-500-30052-7.  Higham, Robert; Barker, Philip (1992). Timber Castles. London, UK: B.T. Batsford. ISBN 0-7134-2189-4.  Cathcart King, David James (1988). The Castle in England and Wales: An interpretative history. London, UK: Croom Helm. ISBN 0-918400-08-2.  McNeill, Tom (1992). English Heritage Book of Castles. London, UK: English Heritage [via] B.T. Batsford. ISBN 0-7134-7025-9.  McNeill, Tom (1992). English Heritage Book of Castles. London, UK: English Heritage [via] B.T. Batsford. ISBN 0-7134-7025-9.  https://en.wikipedia.org/wiki/Beaumaris_Castle  Erlande-Brandenburg, Alain (1995). The Cathedral Builders of the Middle Ages. Découvertes Gallimard ("New Horizons") series. London, UK: Thames & Hudson Ltd. ISBN 978-0-500-30052-7.  McNeill, Tom (1992). English Heritage Book of Castles. London, UK: English Heritage [via] B.T. Batsford. ISBN 0-7134-7025-9.