When I was initially asked to look at the roof, the problem was immedi~ ately apparent. Nearly all the cut branch rafters had been seriously affected by worm and beetle infestation to a degree where many of them had simply broken.

In discussions with Paul White of Broadland District Council and Stephen Heywood of Norfolk County Council, it was agreed that it would be acceptable to provide a ceiling at the level where some collars exist. This gave me the opportunity to consider the form of structure that we could place within the remaining triangular space to pick up every rafter - initially in a temporary situation - but then retained as part of the permanent system of structural support.

After some discussion and thought, I proposed the use of a plywood-faced lattice-girder beam constructed in timber running down the length of the roof supported either off the existing gable brickwork at each end of the gallery or off two new A-frames distributing the load back onto the eaves brickwork. The idea was that load would be transferred from the existing rafters to the plywood beam by the use of plywood gussets profiled to the underside of the distressed rafters, even though rafters were simply hanging in the air. if we could make the structure safe enough for the thatchers to work then we would have achieved our initial objective. This would cause as little damage to the existing roof structure as possible. The plywood beam being constructed is shown in the photograph below.

In preparing our design, we had to take account of the requirement to replace the thatch leaving perhaps 6 in (150 mm) of the existing and providing a new structure over the top to support new thatch. (see sketch). We decided that this structure must be self supporting; thus, we designed a series of Aframes with the collars penetrating the existing thatch and undecorated plaster. In providing a new roof structure over the top at eaves level, the further problem is that it does not bear on the existing brick walls. We have, thus, devised a gusseted support at the base of the rafters to carry the load back onto the existing walls. Fortunately, the additional overhang front and back is hidden by the gable brickwork.

Currently we are at a stage where the plywood beam is in position and the thatcher is about to commence work. I initially thought that plywood spreader sheets would be needed on the existing roof thatch to spread the load, but the contractor - W S Lusher of Norwich - suggested that a system of horizontal scaffold tubes supported from the temporary roof structure would work rather better and this is the current proposal.

In a project of this nature every small piece of opening up suggests a change to the design proposals. it has only been with the help of the conservator and contractors that we can progress the job in a sensible engineering and conservation manner. At the beginning of the work on site I made it clear to the contractors that nothing was written in stone. We would need to be flexible in our approach if we were going to be able to achieve our objective of providing a new thatched roof without damaging the wall paintings. This, after all, is the objective that we are all striving to achieve.