The building of castle walls could be a book unto itself, but we’ll try to hit the highlights here. First, they have to be flat enough to make climbing up very difficult. There are tricks to this. Sure, hiring a clan of dwarven masonry craftsmen to build your wall is an option, but so is plastering the wall. Yes, plastering will likely need to be redone every few years, but it’s still cheaper than the craftsmen (probably) and it makes the castle look all white and new.
Second, they have to be tall enough to make climbing difficult, with or without ladders. Ten feet tall is considered tall enough to stop direct attacks, but not climbing. After all, an athletic man, should be able to jump up and grab the top of a 10’ wall, or at least have a buddy who could give him a boost. A 20’ tall wall could possibly be overcome with a ladder, but a 20’ wooden ladder is likely to weigh about 50lbs. That gets difficult on top of armor, weapons and other gear, in addition to how slow climbing a ladder can be. Ample opportunity to pick him off on his way up. So 20’ is normally considered “high enough”. Sure, you can go a lot higher, but you would need to have a specific reason to go above 20’. Also, the higher you go, the more likely that you will need to add buttressing to hold the walls up.
Castle walls need to have their own defenses. The tops of the walls can have merlons. These are the portions of the wall that stand above the wall itself, providing cover for archers atop the wall. They might have their own arrow slits in them or have the archers simply hide behind them until ready.
But in order to hide behind the merlons, there needs to be a way to walk around the top of the wall. If the wall is quite thick, then walking on the wall itself probably works. If not, then a catwalk might be needed to allow for movement. Anything less than six feet (or whatever measure your rules determine allow two fully grown men in armor to safely pass each other) is too narrow.
One of the greatest ways to stop an opposing force from attacking the wall itself was machicolations. In order to have these, the uppermost portion of the wall (above the walkway) juts out from the wall. This additional portion is supported by corbels, the braces built into the wall to hold the portion that is not in line with the wall itself. Now that there is extra space, the flooring between the corbels can be removed allowing the people atop the wall to look directly down the surface of the wall. In this way, the defenders can pour things down on top of anyone trying to assault the wall. This could be boiling oil, rocks, or simply missile fire.
Walls came in many different styles, but the typical fantasy era wall is about 10’ wide, but not really. Two walls were built parallel to each other, then the space between them was filled in with rubble and mortar. This gave the walls solid surfaces, cheaper thickness, and even a little bit of impact resistance from the filler. What was the rubble? Most commonly the leftovers and scrap that didn’t go into the wall itself. If it were a brick wall, then the filler might be the clickers (burned bricks) or other visually unappealing pieces. Stone walls would often have the gravel created as the stone pieces were cut and shaped, plus all sorts of gravel from the quarry.
We’re assuming that the castle walls are made of stone, but they don’t have to be. We’ll normally consider wooden walls to be “palisades”. Why? mainly because any wooden wall made from lumber (like from the saw mill) would be far more expensive and probably not as strong. It was easier to cut down trees, strip the branches, and then just sharpen the ends of the log. By pounding these logs into the ground and putting some support crossbeams inside, you can put up a fairly decent defensive wall quite quickly.
Placing the towers was a very important part of planning the curtain wall. The towers needed to be placed in such a manner as to allow the defenders to use the walls and the towers to target anyone attacking. If an enemy were able to hide behind the tower itself and therefore be in a blind spot, the defenders were likely in trouble.
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This post was written as part of The Secrets of Siege Magic aka All About Battle Magic for Castles & Sieges, the latest in our Small Bites editions. Each Small Bites book looks deeply at one subject, a character archetype, a race/monster, a style of questing, or some other role-playing/world building subject. This one is showcasing magic used in attacking or defending castles, and then naturally by extension walled cities and other fortresses.
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