Stone keep castles were built in 11th - 13th centuries.
In 1066 by the Normans
All castles that exist today are made from stone because stone lasts for a long time. In total there were three types of castles: Stone Keep castles (Stone castles), Motte and Bailey castles and Concentric castles. The Stone Keep castles were made out of stone along with the Concentric Castles and still stand to this day as great monuments. The Motte and Bailey castles, however were made out of wood and have all rotted away to leave none left standing today.
Stone or square keep castles were first built in Medieval England by William the Conqueror. Stone keep castles were the natural extension of motte and bailey castles. Motte and bailey castles were only temporary features (though many mottes exist to this day) while stone keep castles were built to last. (this was copyed and pasted off the website below.)Go to www.historylearningsite.co.uk/stone_keep_castles.htm for more information.
William The Conqueror. Aka William of Normandy.
1847
A castle which have a series of different sized walls surounding them
Stone castles were built in 1277 and usually had more that one wall, the inner wall being higher than the outer ones.
Motte and Bailey Castles are created on a raised mound which is either natural in formation or built. At the top perimeter of the mound a wooden post fence is built and within this enclosure there is usually a watch tower built. The design probably dates back as far as the neolithic period when hill forts were constructed to protect towns. These type of castles are temporary in nature unlike the stone keep castle which as its name implies is made of more permanent materials and is surrounded by a stone wall. Later versions of stone walled castles employed such structures as gatehouses, moats keeps and watchtowers, including the grander ones having both inner and outer courtyards.
They were built in the year 1172
There is no particular year, but most castles had fires to keep warm. For more information on life in castles read this:http://www.castles.org/Kids_Section/Castle_Story/inside.htm
Top floor :- Areas of the Lord's family and guests. Lord's family sleeping quarters. 2nd :- The Great Hall Dinning Hall Ground :- Guard Room Chapel Underground :- Dungeon Storeroom Cellar More Dungeons Somewhere in the castle :- Spiral Staircase Small, long windows
No one really knows the exact date someone created a castle but obviously they were needed to keep towns safe so to answer your question the Normans invented building castles first by using wood and timber and then even after their the Norman invasion of Britain in 1066 they were still using wood and timber to create castles and then through necessity turned to stone castles.