Although there are no documents about the early years of Guildford castle, it is almost certain that it was built shortly after the Norman conquest of 1066.
Guildford was an obvious site for a castle as it was the only town in Surrey (apart from Southwark). It was also on an important route between London and the south coast and the west of England.
The bailey boundary ran along Castle Street, South Hill, the edge of what is now Racks Close and along a line parallel with Quarry Street but to the east. It may have used part of the Saxon borough boundary. The bailey was probably divided into an inner and outer bailey, partly along the line of the path between the bowling green and the castle grounds.
There was probably a wooden tower on the motte, providing a lookout post for the garrison. In the early 12th century a chalk wall, or shell-keep, was built around the top of the motte. Later, perhaps in the 1130s, a keep, or great tower, was built to one side of the motte. It was probably over part of the shell-keep and also used the natural chalk below the artificial motte to take the weight of the tower.