The wagon vault (ceiling) is attached to an inner wall plate. The stone tiled roof is attached to an outer wall plate. Both wall plates rest on a thick stone wall. Each wall plate is exceptionally large and made of oak. The inner wall plate has been moulded using hand tools.

Parts of the wall plates were missing due to decay. They have been repaired with new seasoned oak using a mixture of traditional joints and modern techniques. Stainless steel has been used to connect the old and new wall plates. This was done to avoid carpentry of old timbers and to ensure a clear distinction between existing construction and the intervention.