Butser Ancient Farm


Principal Christine Shaw

Lessons from the Pimperne House Dismantling.

Reynolds, in Harding, Blake and Reynolds (1993), describes in detail the thinking behind his first Great Roundhouse project and used in the construction of the best available interpretation of the structure of the Pimperne House in Dorset, UK. This was undertaken in part of the grounds of The Queen Elizabeth Country Park, South of Petersfield in Hampshire, UK and in the shadow of Butser Hill, where his first work on Iron Age farming began.

Work on the Pimperne House began in 1976. The house was finally dismantled in September 1990. The lessons from the construction stage have been summarised on a previous page.

This page deals with lessons from the dismantling stage and which were also described in Harding et al. It should be noted that the particular discoveries made when excavating the post holes left behind when the uprights were removed, led to the specific hypotheses and conclusions reported in the lecture and subsequent publication on the Life and Death of a Post Hole.

Dismantling took place over two weeks of work and careful observation and recording covering various features of the building. The whole was in good structural condition, except for the outer porch posts (the most exposed parts) and these had already been replaced because of rotting at the soil interface. Clearly they would have needed replacing again quite soon.

All visible support timbers were in good order and well secured. The worm infestation observed in the first years after construction had penetrated no more than 2 mm into the pith wood. This was found to be so for the rafters, also. Only one principal post had started to rot at the soil interface and no subsidence had occurred. Purlins, rafters and ties were all in an excellent state. The hazel of the purlins had set but, unlike a hurdle fence of comparable age, were not brittle and could be used to scale the roof during inspection. The rafters were hard and fit for reuse. Smoke blackening was confined to the upper third of all members.

The very detailed observations of the deterioration of the main structural posts showed that the early stages of decay did not give the full picture of how post holes appear in the archaeological record and it is the bridge between these two time scales that led to the above mentioned paper "Life and Death of a Post Hole" [link above]. Very briefly, the early decay could be accelerated by any long-term ingress of moisture. However, even when this occurred, the first stage of decay left the bark intact and, where the pith wood rotted rapidly, an air gap developed which generally led to the remaining central hard wood being dry and long lasting. Thus the original stone infill lay up against the bark and no extra infill was inserted in the relatively short life span of the Pimperne construct. The essential hypothesis is that had rotting progressed, over the normal life span of such a house, then there would have been a growing gap that would be filled with the sort of objects and artefacts often found during post hole excavation. The presence of these objects as a post-abandonment feature has always been difficult to explain and the interpretation offered by Reynolds, based on these findings, is compelling.

The sort of degradation observed does not imperil the structure because all loads on the posts are essentially vertical and, as the hole is infilled, the residual post above ground level continues to sit on a firm base. This practice mimics the situation observed with what is seen with more recent cruck-framed farm buildings, where ultimately the support pillars end up on top of a raised stone plinth. In fact, this very process and its success is proof that the building design, both for the Pimperne construct and for the cruck-frame barns, results in vertical loading of the support pillars/posts, for otherwise these would become laterally displaced.

The porch structure is independent of the main structure and its deterioration pattern is not as regular. This may be why post holes around supposed porches are at best distorted and at worst obscure !

"Destroying" the outer wall proved to be the most arduous of all, requiring the use of sledge hammers. The wattle work, once the daub had been removed, was found to be dry and strong and had not become embrittled in the way that exposed field fences routinely and rapidly deteriorate. This must contribute to the stability and longevity of such constructs as this. In a similar manner to the main structural posts, the vertical stakes supporting the wattle were beginning to rot back to the surface but less markedly so in the time scale tested. One suspects the process would end at the ground surface, out of sight, and that the outer wall would rest happily on the ground, held in place by the rigid cylindrical shape.

An incidental observation over the life of the house was that the level of the inner floor varied according to the wear due to passage of people and to cleaning. The variety of patterns of the processes involved are detailed in the Monograph.

Another ancillary record is that after five years the soil fibre content of the inside floor had fallen to about 5%, compared with an initial value for the grassland, prior to construction, of some 24%.

In his final words, Reynolds unwittingly wrote his own epitaph, judging by statements in his many obituaries and in the eulogies on the day to celebrate his life's work :

"That it was an important construction, which fulfilled all the criteria of the archaeological evidence, is beyond question."

It is only fitting that this record be completed with a picture, from the Monograph, of Reynolds approaching completion of the thatching of the Pimperne House construct.

 

 

Reference:

Harding D.W., Blake I.M., Reynolds P.J., "An Iron Age Settlement in Dorset - Excavation and Reconstruction", Monograph Series Number 1, Department of Archaeology, University of Edinburgh 1993.

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Created 01 August 2001 - Updated 4 September 2002