The keep is nearly square, a common shape for Norman keeps. The east and west sides are long and the north-south sides about . The main part of the keep stands more than tall, and the turrets rise an additional above the parapets, commanding the countryside around it from its elevated position atop the ringwork. The walls are about thick at the base and average thick at the top. They are constructed from flint rubble bound with lime mortar, but, very unusually for an Essex castle, are faced with ashlar stone transported from a quarry in Barnack, Northamptonshire.