I have noticed that european castles have been made out of different materials and I realise why this was done (stone would be a lot harder to get than brick in the Netherlands, for example) but I was wondering which would be "better" against a siege involving, for example, catapults and so on.
The comment I first saw spoke of walls of solid rock being better than thinner walls of rack with loads of rubble in-between but is that true?
How well would a castle made of brick respond to such abuse?
Have there been documented sieges using such weaponry against brick castles?
Brick was a very popular building material for castles and urban fortifications in Eastern Germany, Poland the Baltic, the Ukraine and Russia and proved very resilient both against mediaeval mechanical artillery and gunpowder weapons. Some of these fortresses stood up surprisingly well against even WWII era artillery, for example the Teutonic Knights' castle at Marienburg (now Malbork) in Poland.
Re stone walls, building a thick wall of solid cut stone masonry was a very expensive proposition in the middle ages so it was only done comparatively rarely, unless money was no object or you had a source of free cut stone (such as abandoned Roman ruins) near at hand. The more common method of building a stone castle wall was to build two parallel walls of cut stone or coursed rubble as facing for an interior core of rubble mixed with mortar. As the outer facing was valuable and extremely nickable for use in later buildings, at many sites it has been stolen and all that is left is the rubble cores.