Stone Castles, the great evolution in castle design

author icon By George Ghidrai

The Motte and Bailey Castles were very popular for almost two centuries. One of the many things that made this design so popular was the use of wood as the primary building material (which was cheap and easy to use).

However, as time passed, some advanced fire-launching techniques were developed to burn down the wooden structure. Moreover, timber also tends to rot easily, and many of these early castles quickly ran into disrepair.

Motte and Bailey Castle

The original Motte and Bailey Castle, made entirely out of timber and earth

To avoid the perils of fire, improve durability and increase the castle defense capability, castle designers decided to replace (wherever possible) timber with stone.

However, the evolution from the primitive motte and bailey castles (made entirely out of timber and earth) to the grand stone castles was not an overnight process.


Evolution of Castle design step 1: Shell Keep Castles

The first obvious solution to improve castle defenses was to replace the wooden keep with a stone keep. However, this solution presented its own set of issues:

  • Stone was more expensive, harder to manipulate and required a skilled workforce
  • Castle engineers did not trust the motte to support the enormous weight of a stone keep

As a compromise, a common solution was to replace the wooden palisade around the keep and the one surrounding the bailey with a stone wall. That's how the so-called shell keep castles appeared.

Shell Keep Castle

Shell Keep Castle

The idea behind a shell keep castle was to replace the wooden outer wall which had previously encircled the castle with a stone wall. The stone shell contained the existing wooden buildings and acted as a shield against attackers.

The image above shows Restormel Castle, a great example of a former shell keep castle. You can clearly see the stone "shell" surrounding the top of the Motte.

Shell Keep castles were a relatively short-lived design and few were ever built, as the style faded at the beginning of the 13th century in favor of stone castles.

Because castle designers were concerned that a heavy shell may cause the hill to subside, the stone walls that wrapped the castle were relatively small in size and encircled only the top of the Motte.

As you might imagine, the word shell keep only refers to the stone wall around the keep on top of the motte. However, most often, the wooden palisade surrounding the bailey was also replaced with a stone wall. As another defensive measure, castle-inhabitants began to reposition the wooden buildings to back onto the newly constructed stone wall.

Shell Keep Castle Diagram

Shell Keep Castle Reconstruction (Restormel Castle) - credit to Worldhistory.Biz

Shell keep castles faded from fashion at the beginning of the 13th century as the entire castle design shifted from the motte-and-bailey style to fully fledged stone castles which were the next stage of castle development.


Evolution of Castle design step 2: Stone Keep Castles

Where time and money allowed, stone buildings were built over preexisting wooden towers. Stone towers offered greater protection and defensive capability, however, they were significantly more expensive and a much greater effort in the form of manpower and raw material was required in their construction.

In addition, stone keeps needed larger mottes that could support the enormous weight of the stone.

Stone Keep Castle

A reconstruction of York Castle, a good example of a stone keep castle

The entire Motte-and-bailey design (including shell keeps and stone keeps) became less popular in the mid-medieval period, and from the end of the 12th century, a new scientific approach in castle design had emerged. And with this new approach, the great era of stone castles had begun.


Stone Castles: The Grandest and strongest Castles

Stone Castles were the natural evolution after motte-and-bailey castles began to fall from fashion. Stone buildings could be much larger and grander than simple wooden designs, providing more luxurious accommodation for nobles who sought to demonstrate their influence and military power.

The first stone castle built in England and one of the first in Europe was the famous White Tower of the Tower of London, completed at the end of the 11th century. Throughout most of the 12th century, stone castles continued to be built alongside traditional motte-and-bailey designs.

Tower of London, the White Tower

Tower of London, the White Tower


What was so special about Stone Castles?

There were three crucial aspects that made stone castles desirable:

  1. Firstly, the stone buildings were much stronger and offered greater protection against raiders. Stone castles could survive attacks using fire, although some elements (such as roofs) were still made of wood.

    Stone walls offered greater protection against catapults and siege engines that were increasingly used in sieges from the 11th century onwards, although they certainly weren't undefeatable.

  2. Secondly, stone castles would last for centuries (many of them survive to this day) whereas wood lasted a decade or two at best.

  3. And, last but not least, these castles were imposing and monumental buildings that would command huge respect to any noble able to afford them. They became, therefore, the ultimate symbol of wealth and power (both political and military) across Europe.


Stone castles layout

Castle design largely depended upon the local landscape and the purpose and function of each castle. No two stone castles had the same layout, and while some castles were designed to culture an air of luxury and grandeur, others were built for purely militaristic pursuits, with strong walls that could be easily defended and provide shelter for the local population.

Most medieval castles did share some common features, so let’s take a look at some of the most important parts of a medieval stone castle. You can get more information on the castle features if you follow this link while you take a look at the image below:

Stone Castle Layout

Stone Castle Layout (credit to BeanBox)


How were these castles built?

Stone castles were extremely expensive and took a great deal of time to build. If some motte-and-bailey castles could be constructed in less than a month, a medium size stone castle would have taken a minimum of five years to build, while a large size stone castle could take more than a decade.

When building in stone, one of the primary concerns of medieval builders was to have quarries close at hand. As opposed to motte-and-baileys that could be built with unskilled labor, stone castles required skilled workmen such as masons (both cutters and layers), quarrymen, smiths, and carpenters.

These large-scale construction projects led to the development of tools and machines that decreased human effort and speed up the construction process. An example is the wooden treadwheel crane, a human-powered device used for hoisting and lowering building materials such as large stone blocks. These cranes were used during both the Roman period and the Middle Ages in the construction of castles and cathedrals.

treadwheel crane

treadwheel crane

Along with improvements in building technology, the techniques of building wooden scaffolding were constantly improving.


Stone castles drawbacks

By the late 1100s, stone castles became so expensive that only the King and the richest nobles could afford them. While the cost of an exceptionally expensive motte-and-bailey castle was as low as £20, the cost of a large stone castle could go as high as £10,000 or even more.

It goes without saying that in the event that a Castle was destroyed, it would spell financial disaster for the noble owner.

Not only were stone castles expensive to build, but they were a nightmare to look after. Castles were large, cold and frequently leaky buildings and often contained a lot of unseasoned timber. As a result, they needed careful upkeep and their constant maintenance was very expensive.


As castle design evolved, so did the tactics used by raiders to attack them and it was evident that there was a need for further innovation in castle defense. From the end of the 12th century, a new innovation in castle design has emerged. It was time for the concentric castles, one of the high points in Medieval military architecture. Read more about them in the next chapter.


See also