The building is timber framed, constructed mainly of oak; the method of framing is similar to 17th century domestic work with principal posts supporting bessummer rails and wall plates with close studding. The framed walls were sensitively repaired in 1908 and were generally in reasonable condition. However, some ad hoc repairs over the years had left some important frame members in a precarious state.
On the south elevation a false brick plinth had been formed burying the sole plate in brickwork. During repairs it was found that the sole plate had completely rotted away, together with the first 200-300 mm of each of the timber posts supporting the Gable end. It was necessary to piece-in new oak along the whole elevation. The timber frame has been thoroughly repaired, replacing timbers weakened by wet-rot and beetle infestation with new oak. A damp proof course has been introduced to protect the new timber sole plates.
Much of the existing roof slating was in good condition, but it was necessary to remove the slates in order to carry out repairs to the roof structure below. Because the roof would be open for a long period and the building had to be protected with a temporary roof, in itself a massive structure.
As well as repairs to the main hall structure, it was necessary to repair the roof of the Reading Room and the area now used as the toilets, where the distortion of the walls to the main hall had pushed the roof structure of the side rooms away from its original support.
The opportunity was also taken to improve the design of the hidden gutter to the south of the main hall, which in the past had blocked regularly with fallen leaves. The gutters have also been provided with electronic circuits to prevent ice forming in the drainage pipes to the gutters.
In order to repair the frame it was necessary to remove much of the plaster covering the walls. This allowed a comprehensive analysis of the existing framework, particularly around the north front. It became apparent that the building originally had an open portico supported on four circular wooden columns in the positions now occupied by the rendered pilasters. The portico was enclosed at the beginning of the 19th century to form two small service rooms, each with a fireplace. The individual staves of the columns were reused as ceiling joists and still exist in the ceiling of the cloakroom and disabled toilet. The main entrance was where the new glazed draught lobby doors are sited and stairs to the balcony were in the corner of the new cloakroom. These stairs must have been very narrow to fit in the space but as none of the parts have survived, the form can only be guessed.
The roof structure is also an unusual form based on a braced collar truss with cambered collars and arch braces designed to accommodate an arched plaster ceiling. Unfortunately, a combination of a shallow pitch and notching the roof structure to accommodate the ceiling weakened the roof trusses and early in the building's history the roof structure began to spread. Fragments of plaster in the roof space show that the roof truss had sagged at the least 400mm., at which point the ceiling had to be re-plastered. It is thought that the iron ties were added to the roof at this time. The builders seem to have been aware that the trusses were vulnerable to spreading and had attempted to counter this by introducing large diagonal braces topped with ornate corbel brackets in the side rooms. Unfortunately they omitted to tie the soleplates of the braces to the soleplates of the main hall and as the main hall walls bowed they pushed the soleplates of the side rooms up and out. These braces still exist and are located within the south wall of the Mallett room and the north wall of the Reading room.
The major requirement of the structural repairs was to stabilise the roof trusses and prevent further spreading of the main hall walls. New steel trusses have been introduced to the existing structure to support the roof. The existing timber trusses have been left in place and after repair could be used to support the ceiling.
The ceiling plaster was in a very delicate state and it was feared the vibration of mending the roof's structure would cause it to collapse. During the repairs the plaster was supported with scaffolding and a timber framework was shaped to match the radius of the arch. The loose areas of plaster were bonded in position using plaster of Paris reinforced with stainless steel mesh.
The ceiling plaster is supported by timber ribs which, in turn, are supported by binders fixed between each of the roof trusses. The connections between the ribs, binders and trusses have been weakened by the movement of the roof and new fixings were introduced to ensure that the weight of the ceiling was safely transferred to the roof trusses.