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Brisbane's windmill
an account of the conservation process

This paper is an account of a conservation study of the Brisbane windmill, and of conservation works which followed that study. The processes used to investigate cultural significance and decide conservation policy are highlighted, and the windmill project used to illustrate how conservation professionals go about their work.


The windmill on Wickham Terrace is the oldest building in Brisbane and is one of only two buildings that still remain from the Moreton Bay penal settlement of 1824-1842. It was built in 1828 as a grist mill in this role it was not an entire success, as Professor Whitmore discusses in his companion paper.(1) In 1861 the mill lost its machinery and became an observation tower part of a signal station which announced shipping movements by means of flags flown from a tall flagstaff nearby. That was the first and most radical of a long series of changes in the use of the structure; each of these changes reflected the state of social and technical development of Brisbane at the time.

The old mill has been recognised as an evocative relic of Brisbane's past for many years it may well have enjoyed this recognition longer than any other structure in the city.

In 1987 a group of firms involved in the design and construction of the Central Plaza office building in the Brisbane CBD offered to assist the Brisbane City Council in the conservation of the windmill. The Central Plaza Project Team, as the group was styled, offered to contribute $160,000 and their own skill to 'refurbish' the exterior of the windmill. Central Plaza was due to be opened in mid 1988, and the Project Team wanted the work on the mill to be finished at the same time. The Council accepted this offer, and the Project Team arranged for work to begin on the removal of cement render from the walls of the tower.

In March 1988, following unease in some quarters about the proposed 'refurbishment', our office was commissioned to prepare a conservation study and later to assist in the conservation work. The study, and the restoration work that followed, were required to follow proper conservation procedures while meeting a series of tight deadlines.

The conserved mill was opened by the Lord Mayor of Brisbane on 3 November 1988. A sketch of how this was achieved now follows, with some observations about the future of the structure and its site.

The conservation process

Historic places, such as the windmill, are like documents in which we can read about the past. They may have significance to present and future generations because they exemplify either the great achievements or the ordinary life of the past. The evidence contained in the physical fabric of these places requires care to prevent its loss or distortion. A century of experience in Europe has shown how vulnerable this kind of evidence is to distortion through inappropriate 'restoration'. The safeguard against loss of evidence, whether it be caused by natural deterioration or by inept interference, is the application of a rigorous conservation process.

The common wisdom of experienced Australian conservation practitioners is most lucidly set out in the Burra Charter(2) and its supporting Guidelines(3), and some practical aspects of the process have been amplified by Dr Jim Kerr(4). The Burra Charter defines six processes 'conservation', 'maintenance', 'preservation', 'restoration', 'reconstruction' and 'adaptation', and offers guidance on which of these are appropriate in particular circumstances.

More importantly, the Burra Charter promotes an orderly process of investigation, assessment, analysis, synthesis and recording, which is the essential mechanism for protecting the value of the place under consideration. It also points out the need for this work to be done by people with a wide range of skills and experience, using appropriate methods and materials.

The conservation study

Our initial commission was to prepare a report dealing with practical and theoretical issues, and containing clear recommendations on how the structure should be conserved. We undertook to have the report complete as a draft for consideration by the City Council within three weeks. To do the study so quickly and at short notice required drastic rescheduling of the office workload. Since the Project Team's offer to the Council was initially confined to work on the exterior of the tower, our study focussed on this part of the fabric, but had to take account of the whole site.

A study team was quickly assembled: Fiona Gardiner, a consultant architectural historian, was engaged to work mainly on the documents; Jinx Miles, a conservation architect with our office, made a detailed examination of the fabric; Dr Alan Spry, a very experienced stone conservation consultant based in Adelaide, was engaged to advise on the masonry; while I oversaw and coordinated the study. This was a small but effective team the members had a good working rapport based on the experience of having worked together on previous projects and on a common agreement about the process to be followed.

Usually, such conservation studies must begin with detailed searching, sifting and analysis of evidence from original documentary sources this is work which can't be hurried. Fortunately, preliminary documentary research had been done in a very competent way by Janet Hogan for the National Trust and the results were available to us.(5) The scope of our study did not permit further historical research to be undertaken, and we relied heavily on the National Trust report. On matters of detail we consulted some of the original documents, held in the Queensland State Archives.

Jinx Miles examined the structure closely, both to establish the history of its development and to assess its stability and durability. This kind of examination always forms part of a conservation study often the evidence of the fabric extends or contests the history known from the documents, and of course it is essential to know whether the building is about to collapse or fret away. The state of the stone and brick mill tower, and the technical options for its future care were, of course, central questions to be addressed. Alan Spry examined the masonry, looking at the constituent materials and at the mill as a whole structure. He assessed the durability of the bricks, the stone and the mortar as quite low. He tested samples taken from various part of the walls to measure salt content, and he measured dampness with a conductivity meter. He concluded that dampness from rain water entering the walls through the outside surface put the structure at risk.

Armed with information from documents and from the fabric, we prepared a brief account of the historical development of the structure in its social context. This historical account was not written as an end in itself, rather as an introduction to a discussion of the mill's cultural significance. It is an axiom that, if you are to preserve the important attributes of a place, you must first find out what they are. Our discussion of significance examined historical associations, evidence of technological development, symbolic value, the mill as a landmark, aesthetic qualities, and the significance of individual elements and parts of the structure.

Our discussion of significance concluded with the following summary of the mill's cultural significance:


It is the oldest existing structure in Brisbane and is a rare surviving building from the Moreton Bay Penal Settlement. The stone, bricks and timber of the original structure were cut and fashioned by convicts.


It exemplifies an industrial process and technology that is no longer used and which is of great interest. 


During the nineteenth century converted as a Signal Station, the windmill was important as a means of communication of information about shipping. It association with communication continued this century when it was used for pioneering experiments with radio and television.


It is strongly associated with activities and events of the Penal Settlement period.


It is an evocative symbol of the convict past and the evolving history of Brisbane.


It is an important element in the streetscape of Wickham Terrace. Back to text.

It was apparent that the windmill was important for a complex of reasons which related to the history of its development over 160 years. In introducing a discussion of appropriate conservation measures, we wrote in the report:

The windmill as it stands today contains in its fabric the authentic evidence of its history. It has undergone many changes since 1828, these changes reflect the evolving use of the structure. Future care of the windmill should aim to retain this evidence, with the least possible physical interference. The significant aspects of the building are plain to see and it does not need to be radically altered to make these attributes apparent. In fact the significance of the building would be harmed if it were much changed.

As a general principle nothing should be reconstructed without evidence. For example as no documentary or physical evidence exists of the sails and cap of the windmill, so it would be inappropriate to reconstruct these. In any case, part of the significance of the windmill arises from the fact that the building was adapted to be a signal station and fulfilled this purpose for over sixty years. . . . The fabric of the windmill, its deteriorated stones and timbers, provides evidence of its history . . . . nothing should be replaced unless absolutely necessary. For example rotten and damaged timber parts should be replaced only where it is structurally necessary to preserve the whole building.

Deterioration of the masonry walls had been a persistent problem throughout the life of the windmill. As early as 1874 the stonework around the windows was . . in parts cracked and in a dangerous state of decay. It appears that the central brick section of the tower may have been rendered as early as 1861 it was certainly rendered by 1898 when a decision was made to completely render the tower. The existing render, applied in 1950 and partly removed in 1987, was unsound, and it was clear from Dr Spry's investigations that the brick and stone masonry would deteriorate rapidly if its moisture content could not be stabilised.

Alan Spry strongly recommended that the walls should be protected from moisture entry, and his report canvassed the various options. We supported his recommendation to apply a new render coat to those sections which had been stripped of render and to clean, repair and resurface the existing sound sections of render. And we agreed with his rejection of any form of clear water-repellent coating or resin consolidant to the stone and brick surfaces, because of problems of performance, durability and reversibility of these treatments.

In addition to recommendations about the masonry walls, our report also made proposals about minor repairs and repainting of other exterior parts of the mill. Beyond its firm proposals for the preservation of the exterior of the mill structure, our report suggested that the site should in future be explained and interpreted, by means of displays and through appropriate reconstruction. The signal station flagstaff, for instance, could be reconstructed this would demonstrate how the signal station worked, and would not have to take away any significance of the site.

The report was considered by a consultative committee set up by the City Council, and the recommendations were supported without any serious disagreement.

From our first discussions with the client, to the point where the work could begin on the building, a period of about a month had elapsed. This is an unusually short time for undertaking a conservation study of a place as complex and important as the windmill. Three factors made it possible to meet the deadlines without serious compromise in professional standards:


The heavy work of documentary research and preliminary analysis had already been done; 


People with the requisite skills, and experienced in working together, were immediately available to form a study team; 


All steps in the process were closely monitored and coordinated I give credit to Graham Macdonald of Resource Coordination Partnership, members of the Central Plaza Project Team, for this important contribution. 

Carrying out the work

Preparation of specifications and schedules of work had begun in advance of finishing the draft report, so that work could start on the building as soon as approval was given. The work was done by specialist tradesmen, engaged by the Central Plaza Project Team. The role of our office was to prepare documents and to oversee the work.

Conservation of the masonry walls was the major task. This began with the removal of all cement render from the lower stone section of the tower, up to the level where the stage had originally been. Joints in the stonework were repointed with lime mortar.

When this stonework was all exposed to view, perhaps for the first time since 1898, the structure was photographed with a metric camera by the Australian Survey Office as part of the ongoing Australian Heritage Commission/Australian Survey Office Heritage Photogrammetry Project. This is a rapid and accurate method for recording the form and detail of the building. Black and white photographs were also taken with a 4"x5" format camera. The photography was intended to make an accurate and durable record of normally hidden parts of the building, which could be studied at leisure later.

As soon as the photography was finished, a scaffold was erected to give access to all parts of the walls, and the old render was removed from the stone section at the top. Again the usually hidden parts of the masonry were photographed with the large format camera it was not possible to make a detailed photogrammetric record of this upper section, but the 4"x5" negatives record a useful amount of information about the stonework, including the early replacement of some of the stone blocks. A small part of one of the sandstone blocks had broken off, which required a repair with epoxy resin and copper dowels, but otherwise only repointing was called for.

Where the old render was removed, a completely new rendered finish was applied, consisting of a scratch coat of lime mortar followed by a render coat of cement-lime mortar. Where the old render was sound it was left in place, cleaned and coated with a new render coat to match that used on the other parts. The render coat was marked out in imitation of ashlar, as had been done before. A clear penetrating acrylic sealer was brushed onto the render coat when it was dry. The purpose of this finishing system was to completely prevent water from getting into the walls from the outside.

The timber lintel which spanned the doorway at the base of the tower posed some interesting problems. This heavy hardwood beam, probably hewn and installed by the gang of convict workers who built the walls, had been extensively eaten by termites and was incapable to providing any support to the masonry above it. Cracks in the stonework showed that there had already been some settlement. We asked Colin Crisp, a Sydney-based structural engineer experienced with epoxy resin stabilisation of historic timber structures, to examine the lintel and advise us. Following his recommendations, we approached a specialist contractor for advice on the practicalities of in situ epoxy consolidation and for cost estimates. We also considered alternative schemes: removing and replacing the lintel after consolidation in a conservation laboratory; removal to a museum and replacement with a new timber lintel; and permanent propping. We presently favour removing the original lintel to a museum where it can be preserved and displayed, and the installation of a new lintel in the building. In any case, it was decided that time and money were not available to carry out any of these procedures, and that the stonework should remain supported by temporary props.

The timber Observation House on the top of the mill, which dates from 1909, was repainted in its early colour scheme, determined by microscope examination of the paint layers. Sliding window sashes were reconstructed, based on the clear evidence of old photographs and of the fabric of the building these windows had been replaced with glass louvre windows in 1950, and it was decided that the louvres were not significant and that they tended to obscure appreciation of the value of the building.

The flat metal roof at the top of the tower had in the past been fitted with a gutter, but the gutter had been removed around 1950. Without the gutter, rain that fell on the roof simply ran onto the tapered walls below. We were concerned that this increased the stress of moisture on the walls, and we arranged for replacement of the missing gutter. The gutter forms a circle in plan and was neatly fabricated of sheet copper. Old photographs allowed us to reproduce the general form of the earlier gutter with its downpipe and rainwater head all the new elements were date-marked.

The timber casement windows in the tower were repaired and painted, as were the doors at top and bottom of the building.

With the allocation by the Council of Bicentennial funds to the project, the scope of work was expanded to include stabilisation of the internal timber floors and spiral stair, making the time ball workable, and building a new flagstaff as a replica of the one which flew the signal flags.

The timber floor structure, built in 1861 during the Signal Station conversion, had suffered some minor rot and termite damage, and was not safe for public access. The spiral stair installed at the same time was also unstable and unsafe. While perhaps of lesser significance than the work of the penal period, these internal timber elements were still important parts of the structure and care was taken to safeguard authenticity by introducing only the bare minimum of new material. Where rotted or ant-eaten sections of timber were removed, they were replaced with new timber which was readily identified, on close inspection, by means of neat punch marks showing the year 1988. A small number of steel reinforcing plates were called for these were date-marked in the same way. In this work we were advised on matters of structural adequacy by Maunsell & Partners Pty Ltd, who were members of the Central Plaza Project Team Steve Turner was the engineer responsible.

The stair had been built around a central cedar pole into which slice-of-pie shaped cedar treads and risers were housed. An hexagonal drum of vertical pine boards surrounded the stair and supported the treads at their outer edges. Distortions in this structure had allowed the treads to slip out of their housings. Small amounts of new timber and new fastenings, and careful refitting, restored the stair's lost structural integrity. With long use, the cedar treads had worn thin and their nosings been damaged or removed they could not sustain traffic indefinitely. Each tread was fitted with a protective timber nosing and a protective pad of tempered hardboard.

The time ball a copper spherical shell on an iron armature still survived on the pole on top of the tower. This was fitted with a new wire halyard, and a winch was provided for working the time ball by hand for the opening ceremony. The winch was a standard yacht self-tailing capstan winch, installed in such a way that it could be removed without having damaged the building.

Probably the most noticeable alteration to the site caused by the project has been the addition of the flagstaff. This was built as a replica of the pole which was put up in 1865 and removed in 1949. Careful examination of the many old photographs of the site provided quite detailed information about the way the original was built. The new pole was made by the Millcraft boat yard of laminated Oregon.

We thought the flagpole would help to evoke the form of the site in the Signal Station period and would have a useful interpretive role. We did not think its presence on the site would take away from the site's cultural importance except that we were very concerned about the substantial footings needed to support the pole and its three stays. We knew that evidence of past use of the site would be contained in the ground this archaeological resource, once disturbed by ordinary excavation, would be destroyed. Thorough archaeological investigation of the whole site would take more time and money than were available. At first we advised that the flagpole reconstruction should wait until better resources were available, but our clients pressed us to find a way. Our first suggestion to mount the flagpole on a temporary above-ground base was rejected. Our next suggestion was accepted: to commission a consulting archaeologist to excavate just the footings for the base and the stays.

This limited archaeological dig turned out to be an effective compromise. Gillian Alfredson, who did the work, found remains of the original flagpole base, proving that the positioning of the pole was correct. The other evidence she found has been documented in a report. It will add to the understanding of the site, especially if a more extensive archaeological investigation is carried out later.

The future

The project I have just described has helped to preserve the mill for the future, and has protected its cultural significance in the process. It has also gone some way towards the appropriate care and interpretation of the site. Positive treatment of the termite-damaged lintel still waits to be done, but the structure is held in a stable state until this can be done.

The mill and its setting make up a place of outstanding cultural significance. The whole site, with its rich layering of physical evidence of different themes of Brisbane's social and technological past, should be the subject of the same kind of conservation process applied so far only to the mill.



WHITMORE, R., "The Industrial Archaeology of Brisbane's Windmill". Institution of Engineers Australia (Queensland Division), Queensland Division Technical Papers. A companion to the present paper. Back to text.


AUSTRALIA ICOMOS INC. The Australia ICOMOS Guidelines for the Conservation of Places of Cultural Significance (The Burra Charter), 1981. Back to text.


AUSTRALIA ICOMOS INC., Guidelines to the Burra Charter: Cultural Significance & Guidelines to the Burra Charter: Conservation Policy, 1985. Back to text.


KERR, J S, The Conservation Plan: A guide to the preparation of conservation plans for places of European cultural significance. Sydney, National Trust of Australia (NSW), 1985. This second edition includes an appendix containing the three Australia ICOMOS publications cited above. Back to text.


HOGAN, J., The Windmill of Brisbane Town: A study of the social and structural history of the Windmill Building, Wickham Terrace, Brisbane. Report for the National Trust of Queensland, 1978. Back to text.

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