Dr VARMAN's
OLD GOVERNMENT HOUSE
PARRAMATTA
ARCHAEOLOGICAL REPORT ON TEST TRENCHES TO DETERMINE THE NATURE OF THE FOUNDATION SUBSOIL
REPORT FOR THE NATIONAL TRUST OF AUSTRALIA (NSW)
BY
DR ROBERT V J P VARMAN ARCHAEOLOGIST
IN CO-OPERATION WITH ENGINEERS OVE ARUP AND AUSTRALIAN SOIL TESTING P/L
INTRODUCTION
Within recent years cracks have begun to appear throughout most of Old Government House, including the North and South wings. In an effort to understand the root cause of cracking, the firm of Engineers Ove Arup offered their expertise to the Trust by analysis of the subsoil strata upon which the foundations rest.
The trench sites, once determined,were given numerical and directional designations and work commenced on Thursday August 14, 1997 under archaeological supervision. The work continued on the 15th, 18th, 19th, 20th and 21st. The clay was so hard and the trenches deep, that the excavation exceeded the original estimate of two or three days. Core samples were taken of the foundation subsoil strata using U50 tubes in each of the excavated trenches for analysis. A by-product of this investigation was of an archaeological nature; namely to determine the nature of the footings during the various construction phases from 1799 to about 1816/1817 and to keep watch for any evidence of pre-1799 activities: for example, evidence of the 1790 Government House and out- buildings. A Section 60 was obtained from the Heritage Branch for the excavations.
Those involved on site were Ian Goldschmidt, Laboratory Manager of the Australian Soil Testing Pty Ltd who took the core samples. The men doing the excavation were Glyn Fenton and Michael Ladd of the Hambledon Garden Centre
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and the contact for the latter firm was Geoff Lee. Mr Gus Aranega, Properties Manager of the National Trust of Australia (NSW) organized the works and participants. Our thanks are extended to the curators and guides involved at the house while we were there.
The methodology was to excavate carefully where cultural material was found and any artefacts retrieved. Soil samples were collected by Mr Goldschmidt. The excavations were recorded photographically and in drawn plans and elevations. Any early or significant structural features were not to be disturbed. The site documentation was based on previous reports I prepared on the site for the National Trust of Australia (NSW).
The engineer's report is to be presented separately. This brief report is organized according to the areas excavated (see site plan) as follows:
Trench 1 (south elevation of the 1799 Hunter phase, west side of the cellar entrance).
Trench 2 (north elevation of the 1799 Hunter phase, west side of the cellar entrance).
Trench 3 (west elevation of the Macquarie phase of the main house, north end near the north-west corner).
Trench 4 (west elevation of the Macquarie phase of the main house, south end at the north-west corner).
Trench 5 (North Colonnade, east elevation, below (north) door).
Dr Robert V J P Varman,
Archaeologist & Heritage Consultant.
August/September 1997
Old Stone Pine, descended from the First Government
House Stone Pines. In the background Old Government House,
Parramatta, 1799/1816
EXECUTIVE SUMMARY
-The footings in four out of the five trenches rested on a solid shale/clay deposit. The one exception did not involve a heavy load-bearing wall. The extent and nature of this (including site samples taken from the archaeology room) is to be presented by the engineers.
-The 1799 infill deposits found along the edge of the 1799 foundation walls contained large and small fragments of terracotta roofing tile, indicating that the 1799 house was originally tiled.
-The differences in foundation treatment seen at trenches 3 and 4 indicate differences in phasing of the two ends of the Macquarie addition to the 1799 Hunter house, hinted at in my previous reports.
-Proof was found that a doorway existed in the east elevation of the North Colonnade but further exploration would be necessary to determine whether the doorway dated to the original construction period or the 1830s.
-No proof was found of former paving on the west side of the main building but only the area along the wall could be examined.
-The stratigraphy to the west of the building was found to be well preserved.
-The stratigraphy against the 1799 Hunter house was intact below 700mm-800mm (the 1969 agricultural drain destroyed the upper layers).
Trench 1 (south elevation of the 1799 Hunter Phase, west side of the cellar entrance).
1799 foundation wall to the right. The slightly darker deposit, lower right is 1799 backfill of top soil, discarded bricks and tiles. The tiles strongly suggest that the 1799 to ca 1812 house had a plain terracotta tiled roof. The pit shown here is approximately 1.5m deep. The agricultural drain (mid - note pipe) dates to 1969. See below.
West elevation of
trench
This trench was begun on Thursday, August 14 with the removal of the 1969 50mm thick flagging. A strong Portland cement was used to secure the flagging in place. Despite care taken on site, some of the flagstones chipped and a few fractured. There was evidence of settlement of the flagging on the east side of the house between 30mm and 40mm over the last 28 years.
The trench extended from the west flagstone to the cellar entrance to the east down to the base of the 1969 agricultural drain, about 1570mm in length and 800mm wide but sloping inwards toward the foundation. The trench from the 1969 level to the base of the foundation took place directly under the cellar window. The clayey soil was very difficult to excavate, hence the longer time necessary than originally planned.
1969 Evidence
It was an unexpected surprise to find that a wide and deepish trench had been dug along the foundation walls in 1969 approximately 550mm wide and 800mm deep to act as an agricultural drain. The trench narrowed as it became deeper to a minimum of between 300mm and 400mm. Unglazed terracotta pipes of a 95mm bore were installed in the base of the trench butted end to end without the use of mortar or cement and were found to empty into the 1909 entrance to the south cellar through a small vertical rectangular slit. A layer about 13mm thick of medium sized, screened, blue metal was packed around the pipes over which some originally clear plastic sheeting was laid (seen clearly at Trench 2). Over the blue metal was a thick layer of unwashed river sand (grey in colour) approximately 350mm thick. Over the unwashed river sand a layer of washed river sand approximately 200mm thick. The flagging was laid on the fairly compacted river sand but had settled as noted above. The cause of the settling could have multiple explanations: excavation by ants (there were hollows under most flags with the exoskeletons of invertebrate creatures, two shells of micro terrestrial mollusca were found); further sand compaction; and soil movement.
The brick work of the 1909 cellar entrance and the 1799 brick foundation wall, where exposed by the trench, were cement (of a Portland mix) rendered. The original stone sill of the cellar window was exposed, approximately 85mm below the present surface.
It is clear that a trench was dug as an agricultural drain on either side of the 1799 Hunter building in 1969 to reduce rising damp problems. The replaced solid clay deposit with compacted sand may have contributed to the shifting of the foundations but that is for engineers to determine.
The drain had to be removed to reach the base of the 1799 foundations.
1909 Evidence
In 1909 a pit was dug to extend (?) the entrance into the cellar and walls of dry-press brick constructed. The building was virtually gutted in 1908 and a fair amount of early building materials scattered about with later material resulting in the raising of the soil profile; note the original sill of the cellar window now below ground-level. Some of this material was recovered when the trench had to be widened of access. Remains of the glazed terracotta 1909 downpipe drain were found.
1799 Evidence
After the agricultural drain was removed, the trench was taken down to foundation level. This brought up 1799 surface material, a rich loamy clay soil, dark brown in colour, and brick and roofing tile fragments used as back-fill between the 1799 foundation and the original pit dug for the cellar. This is very interesting because it is strong evidence that the Hunter Government House was roofed with terracotta tiled. This complements a 1812-1814 demolition deposit found in the archaeology room dating to the early Macquarie period demolitions when the extensions began behind the 1799 building. The roof was shingled after that.
The original excavation for the cellar probably took place late in 1798. From our trench excavation, it is clear that that the original excavation had sloping sides of a minimum width of 750mm at the top to probably less than 200mm at the base of the 1799 foundation wall. There was no special treatment for the footings, no lower plinth course, just the brick wall of the cellar laid on grey shale (Shale and shale clay). The wall is only about two or three courses below the present internal paving of the cellar. The bricks and shell-lime mortar were similar as elsewhere in the 1799 structure: no evidence of original render below ground.
Ian Goldschmidt took samples of the grey strata under the first course of the brickwork, and lower.
Trench 2 (north elevation of the 1799 Hunter phase building, west side of the cellar entrance).
This trench was begun on Friday, August 15 after the removal of the 1969 50mm thick flagging. As elsewhere, strong Portland cement was used to secure the flagging in place. There was evidence of settlement over the last 28 years of the flagging of between 30mm and 40mm, and even greater, along the 1799 house and ca 1816 North Colonnade. The ground level is approximately 185mm lower than at trench 1 (assuming that the two sill levels are the same). The surface of the 1969 flagging level was set just below the sill of the cellar window, at trench one it was about 85mm below the surface.
The trench extended from the west flagstone to the cellar entrance to the east and down to the base of the 1969 agricultural drain, as at trench 1. Here the trench was made about 700mm wide at the top but sloping inwards toward the foundation. The trench from the 1969 agricultural drain level to the base of the foundation took place directly under the cellar window. The clayey soil was very hard.
1969 Evidence
The same 1969 agricultural drain was found here as in trench 1. Here there was evidence that machinery was used to excavate the drain, as the 1909 glazed terracotta downpipe drain was found to be crushed.
The 1799 wall and the 1908 brick entrance to the north cellar were cement rendered in 1969, whether this indicates that the whole of the building was re-rendered them (high Portland cement content) is not certain. However if the structure was re-rendered with cement, it may have contributed to the cracking because this would not have allowed any sort of flexibility as the subsoil below expanded and contracted, resulting in the build up of stress at certain points.
The sequence of deposits was slightly different here, besides the lower level of the sandstone flagging. The base of the unglazed terracotta pipes was about 700mm below the surface. The deposit of medium screened blue metal was only about 80mm thick and there was strong evidence of a layer of clear plastic sheet having been laid over the blue metal.
Over the blue metal and plastic was a 150mm (maximum) layer of 1909 plaster - with a number of pieces of cornice retrieved. The plaster was very soft and crumbled to white powder as it was removed - it seemed that it was made of partly unconsolidated Plaster of Paris with a harder outer edge. It seems now that some of the ceilings were renewed in 1969, the material being thrown out of the windows. The workers at the time seem to have swept some of this material into the trench for the agricultural drain.
Above the plaster layer was a layer of unwashed river sand (grey hue) of 400mm thickness (minimum). The light unwashed river sand layer was not seen here, unless directly under the 50mm thick flagging.
1909 Evidence
The surface deposit next to the 1969 agricultural drain was made up of hard packed surface soil mixed with demolition rubble from the 1908 overhaul. A trench for the down pipe drain of glazed terracotta interlocking pipes had been cut across this area in the direction of the west side of the cellar window, similar to trench 1: the only remains of this trench and pipe is to be seen on the north profile of the excavation. The infill of this 1909 drainage trench also contained material from the 1908 demolitions.
Though the plaster found in the agricultural drain was deposited in 1969, the fabric relates to the 1909 rebuilding phase (removed in 1969).
1799 Evidence
Above. Fragments of 1799 plain sandstock roofing tile (single plug?). Note the 'drag' marks of the stock on the smaller fragment. The stock was used to scrape off excess clay.
The excavation for the 1799 cellar was wider on this side than the south side, being 350mm-400mm wide at the base. The upper side of the 1799 excavation was difficult to determine because of later soil disturbance.
The nature of the brick foundation was the same as in trench 1, as were the hard clays and the foundation subsoil of grey shale and clay.
The 1799 back fill was of a brown compact clay soil with fragments of brick and roofing tile from the construction of the 1799 house.
Trench 3 (west elevation of the Macquarie phase of the main house, north end near the north-west corner).
This trench was begun on Monday August 18th. The 1969 flagging had to be taken up to allow for the excavation.
East
Elevation
1969 Evidence
A shallow trench along the wall was found here as at trench 3. The purpose was to cement render the walls to approximately 200mm below the flagging. Here there does seem to be evidence that the walls were re-rendered in 1969. The fill in this shallow trench, against the render, had definitely Kings School- related artefacts; a tennis ball and a marble. The deposit also contained fragments of earlier cement render (most likely from the 1908/1909 reconstruction period, supporting the idea that at least parts of the exterior wall were re-rendered in 1969. The material found in the plaster dump to the west of Old Government House did contain some fragments of cement render but these were almost certainly from 'patching' episodes dating from after the 1870s. There was also demolition material from 1908, fragments of brick and early mortar.
Also in the fill deposit were lumps of asphalt, both in this trench and that of 4. This suggests that there was asphalting done during the Kings School period but whether it was the whole yard or just a path cannot be determined from the trenches. Evidence of former paving was looked for but not found, though it should be kept in mind that areas along the walls of structures are often more frequently disturbed than areas further out, such as work on rendering and service trenches.
The yard surface was evidently compacted in 1969 without too much damage to the stratigraphy below. The compacted material is similar to the deposit along the edge of the wall. Washed river sand was spread across the yard and the flagstones laid on that deposit.
1909 Evidence
The glazed terracotta pipe carried off water from the downpipe formerly located there. Material from the 1908 demolitions and earlier found its way into the trench infill of the terracotta pipe and layers above that.
1812-1816 Evidence
South
Elevation.The original foundation trench can be seen from the mid to
lower right hand side. A crack appeared along the line as the clay
dried out.
The original trench excavated for the foundations of the early/mid Macquarie extensions to Old Government House were clearly seen in profiles of the north and south elevations of our trench. The trench was very narrow, tapering from about 200mm at the top to as narrow as 35mm at the base course of bricks. These contained brick fragments from the construction phase and a number of small fragments of roofing tile from the demolished roof (sheathing , at least) of the 1799 phase. Again it seemed that surface material was used to backfill the foundation trenches.
The base of the base course of bricks is about 780mm from the flagging surface. As in trenches 1 and 2, it rests on grey solid shale and clay.
The main difference in the construction of the footings compared to trench 4 is the base course of bricks which steps out by about 40mm to 50mm, like a plinth. This is significant and lends support to previous evidence that suggested that the west Macquarie addition was not constructed at one time. Not enough mortar could be retrieved from between the bricks to determine if there were any differences (soil contamination extended in at least 10mm from the face of the brickwork.
1790 Evidence
Only one brick fragment was positively identified as from the foundations of the 1790 structure (kitchen?). The position of our trench would have been in the middle of the 1790 structure. It was noticed that there was a distinct horizon between the undisturbed subsoil about 300mm-350mm from the present flagged surface (showing some pebble displacement from trees or shrubs growing in the area probably before it was cleared). Overlying this a deposit of neutral tan-reddish clay, probably displaced soil during the 1790 construction. No typically underfloor deposits were discovered.
Trench 4 (west elevation of the Macquarie phase of the main house, south end at the north-west corner).
Begun on Tuesday August 19. A complex area but having similar deposits as at trench 3.
1969 Evidence
As for trench 3. The concrete pad for the metal plate could be seen in profile on the north elevation of the trench. Glazed terracotta pipes relate to the present downpipe near the corner of the south elevation of the building. The backfill was similar to the backfill along the wall (down to the depth of the cement render), asphalt, fragments of cement render, brick and some stone.
1909 Evidence
An iron pipe, approximately 95mm in diameter, was found to run in a
north-south direction about 400mm west of the building wall and 430 deep from the flagging surface. This is more like a pipe used for sewerage (not seen at trench 3). The size of the trench for the pipe, which can be traced in the soil profile, is unusually wide: the backfill contains brick fragments probably from the 1908 demolitions. Here remnants of the original soil profile is as shallow as 220mm.
1812-1816 Evidence
Here the original trench for the Macquarie foundations is very narrow, 90mm at the top, narrowing to less than 20mm, away from the brickwork. The backfill contained a few fragments of brick.
Here also the foundations were found to rest on the grey shale/clay deposit (as in trenches 1, 2 and 3).
Ian Goldschmidt needed one area where the foundations did not reach the solid grey deposit, so a new site was chosen under the east door of the Northern Colonnade.
Trench 5 (North Colonnade, east elevation, below (north) door).
Begun on Wednesday, August 20. This trench site was chosen, in part, because it had already been partly disturbed during works in 1995 and previously in 1969 when, as it turned out, the former steps were removed.
This was the only area where the foundations were not on a solid shale/clay base.
1969 Evidence
A wide trench was excavated, as much as 750mm away from the wall so that the walls could be cement rendered to a depth of 300mm. The backfill consisted of building material mainly from the 1909 demolitions, brick fragments, plaster fragments, several phases of shell lime mortar and cement render. A large submerged stone was scraped and shifted slightly during this phase (the stone turned out to be a base stone relating to the stairs, or steps, here, demolished 1908).
The flagstones are set on a thin layer of washed river sand; and have dropped by 33mm.
1909 Evidence
Mainly building material from the 1908 demolition, further disturbed in 1969 during the re-rendering of the exterior wall. A large stone was found which is almost certainly the base of the last step from the door above. The edges of the stone on the underside were choked with small pieces of sandstone (these proved that the big stone had been shifted slightly). There were also some bricks and another small stone, part of the same base.Dr Robert V J P Varman, Archaeologist & Heritage Consultant. Aug.1997
From the south-east corner. Note base stone
of old stone steps.
ca 1816 Evidence
A quite wide trench was excavated for the construction of Colonnade wall, a minimum of 700mm for some unknown reason. The backfill contained brick fragments from the construction period. The stairs, or steps, were probably constructed after 1816 because the remains begin above the backfill. I would suspect that the steps were constructed during the 1830s when the colonnade was given an overhaul (the yellow shell lime period) but see comments in relation to the base of the wall footings.
The footings are quite shallow, beginning just 550mm below the present level of the flagstones. Unlike anywhere else, the base course of the Colonnade wall footing appears to be of bricks set on edge. From other studies I have made on Old Government House, the Colonnade is later than the main building Macquarie extension and very likely later than the North Wing. Perhaps a different set of builders were responsible for this area.
There is another explanation regarding the base course of bricks on edge, considering only a small section of the wall was uncovered below the door: very often in earlier buildings bricks are set on edge under the location of doorways. If that were the case here (note the change on the base course, right hand side), the bricks on edge may be proof there was a door here from the construction period. We would have to extend the excavation a little further (or check the area from the underfloor area).
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