You go to the store and ask for stones a lot then go home and build.
This depends on what type of castle your referring to. In the Norman times, there were two different types of castles built. There were Motte and Bailey castles and Stone keep castles (Stone castles). The Motte and Bailey castles were made out of wood and the Stone keep castles were made out of stone (obviously).
Stone keep castles were built in 11th - 13th centuries.
Old castles are mostly built of stone.
stone castles were built with stone
Stone castles were built because they could not burn down as ealsily as wood castles can.
Stone
William the Conqueror built two stone castles; Chepstow and the Tower of London. These were the first buildings in England that were not churches to be made from stone, and they were designed to impress and intimidate. Castles made from stone was an idea that did not catch on until the 12th Century.
Medieval castles were built for protection and not for comfort. The first castles were built using wood but, were found to burn easily. Stone was then used in replacement of wood.
motte and bailey castles were the first castles built by william and later stone castles came around they were first rectangular but then were made circular which was better defence. e.t.c. ;-)
Castles in Europe were made out of many different materials depending on what type of castle it is. For example, Motte and Bailey Castles would have been built out of wood and Stone Castles would (and still are) made out of stone because it is stronger and more sturdy.
Castles were built out of stone or brick
They were built with stone and in square shapes lolololololl