Conservation Report - a case for Monteath Mausoleum
By Kin Hui
Executive Summary
This report includes pathology mapping and my proposal for intervention to the Monteath Mausoleum, a monolithic stone building in Glasgow Necropolis. This report examines critically the different technologies available for the purpose of intervention on built heritage. It laid down the principle and guidance for conservation strategy of the mausoleum.
(A) BACKGROUND
(1) DESCRIPTION OF SITE
Necropolis is a category A listed cemetery which was included on the list of monuments on 15 December 1970. This site also entered into the list under Historic Environment of Scotland on 1 July 1987. The main access to the site is from the direction of Glasgow Cathedral via a historical footbridge which spans across Wishart Street.
As shown in Fig. 1, Necropolis is situated on a hill with its top overlooking the city of Glasgow. The top of hill is +146m above the sea level. Beside of multifarious architectural monuments straddling over the hill, Necropolis is also a landscaped conservation area with meandering paths running in zigzag manner over its sloping terrain.
Fig. 2 indicates Monteath Mausoleum in a red dot which is located at the brow of a hill overlooking the south of the city. The mausoleum is situated near to the edge of a steep slope. The exact coordinate of the mausoleum is 55°51’41.7”N, 4°13’57.4”W. Its front entrance orients towards the eastern direction. Monteath Mausoleum is one of the largest and most decorated monuments in the Necropolis.
(2) NECROPOLIS AS VICTORIAN CEMETERY
Due to the industrial revolution in late 18th century, it witnessed an unprecedented growth in population for the city of Glasgow during the early Victorian era. The idea of building a new cemetery sprung from the poor sanitation and unhygienic conditions of the existing burial grounds in the city. It can also be considered as a product of capitalism as the Merchants’ House, the institution that owned the site at that time, saw it a lucrative undertaking to convert the hilly outcrop into a fashionable garden cemetery for the Victorian elite.
The Glasgow Necropolis was modeled on the picturesque Pere Lachaise which was the first and largest municipal cemetery of Paris built in 1804. Being named as Necropolis, the cemetery was to take on a secular theme with grand gesture to impress the visitors. Fig. 4 is a historical photo showing the panorama view of the Necropolis from its entrance location during the Victorian era. The red circled area is the Monteath Mausoleum that stood prominently on the brow of a hill.
(3) BRIEF HISTORY OF MONTEATH MAUSOLEUM
The mausoleum was designed by the Scottish architect David Cousin of Messrs. Cousin and Gale in 1842. Major Archibald Douglas Monteath was an officer of the East India Company. He shares the mausoleum with his brother, James Monteath Douglas. Albeit its intricate stone carvings in facades, one can find no mention of names of the decreased neither inside nor outside the monument.
(B) PATHOLOGIES MAPPING
(4) List of Pathology
Fig. 6 is extracted from the illustrated glossary on stone deterioration patterns published by ICOMOS in 2008 which formulates the standard practice for conservationists who work on built heritage. It defines the terminology of stone decay for monuments.
Under the ICOMOS’s glossary, the pattern of stone decay is categorized into five major sections:
(1) Crack and Deformation;
(2) Detachment;
(3) Features induced by material loss;
(4) Discoloration and deposit; and
(5) Biological Colonization
As revealed in the pathologies mapping, erosion and black crust are the two major pathologies identifiable in Monteath Mausoleum. Erosion is under category (3) and black crust in category (4).
(4) List of Pathology
(5) Overall Observation
Fig. 7 shows collage of facades photos for Monteath Mausoleum so that it will generate an overall picture for the assessment of its conditions. Facades at entrance (SE1, NE1), and those north facing facades including NE2, NE3, NE4, NW4 are identified with severe black crust. Erosion is the most serious at entrance (SE1, NE1) and the southeastern facades including SE2 and SE3. For facades near the steep slope edge, that is NW1 and SW1, we can find at high level with very wide open joints near the roof eaves of the circular structure.
Extensive black crust is shown in fig. 8 at facades which orients toward northeast and northwest. This can be explained by the fact that the said location is always under sheltered from the sun. It prevents the drying up process of the stone wall. Because of the industries that once existed in Glasgow, pollution in the air emitted harmful particles which caused the crust formation on the stone surface.
(6) Detailed mapping by facades
(C) CAUSE OF DECAY
Due to its peculiar location at the brow of a hill, the Monteath Mausoleum has been subjected to constant attack by the prevalent wind since the days it was built in the 19th century. While wind velocity increases with attitudes, the wind effect is exacerbated by the openness of site where the monument is situated. Another reason that accounts for the wind erosion lies with the circular configuration of mausoleum. Vortex shedding will take place when wind flows around a circular object under the law of fluid-dynamics. Vortexd turbulence will be created in the lee side of the building in the wake of the wind’s prevalent direction. With wind predominantly coming from the south to southwest in Glasgow, it leads to the entrance porch and its adjoining facades being subjected to undue wind pressure due to vortex shedding. This is further complicated by the niches and recesses along the façades which tend to heighten the vortex effect.
Stone sample of mausoleum was tested in the laboratory which yielded the result of high content of gypsum in the wall of mausoleum. The Giffnock sandstone, which was used for the construction of mausoleum, is carboniferous in nature. Its petrography reveals its relatively inferior interconnectivity by the intrinsic nature of stone. With the presence of gypsum, stone decay will easily take place under acid rain conditions. We have to bear in mind that Glasgow has rainfall throughout the year with the wettest during the winter seasons. High intensity of dampness will be trapped inside the monolithic structure. The built-up of damp conditions is further aggravated by blocking up of the window openings at the circular portion of the structure. All these factors contribute to the accelerated erosion to take place under the chemical reaction induced by dampness in the structure.
One common occurrence in the facades is the open joints with widened gaps which allow large amount of moisture penetration to extensive areas of the structure. This opens up the vicious cycle of material decay for the monuments. For the last couple of years, plant growth on the pitched roof has increased over time as shown in our conditional survey. The roots of vegetation will penetrate into stone joints that will bring out water penetration and stone disintegration. Routine maintenance needs to be stepped up to halt the further deterioration of the monuments.
Another issue that requires urgent attention is related to the ground conditions of the site where the mausoleum is situated. Due to its proximity to a steep slope in the southwest location, it draws the concern with the structure stability. By visual inspection, one can obviously tell that the entire structure is slightly tilted in one direction. Some parts of the plinth at the inner corner of façade SE2 near to the entrance portico has half sunken into the ground. We identified at roof eave of façades NW1 and SW1 with joints misalignment too. Therefore, it will be likely differential settlement taking place in the structure. This has to be further ascertained with monitoring on the ground conditions and the joints width over a reasonable duration.
(D) INTERVENTION
(7) Philosophy of Intervention
Philosophy in conservation embraces the concept of value. Alois Riegl, the Austrian art historian, touched upon the issue of antique value, historic value and intentional commemorative value. In other words, one needs to approach in the perspective of authenticity and integrity. Any intervention shall not be damaging to the subject artifact or the built heritage. Repair works need to be kept to minimum required to stabilize the monument. The nature of work shall be reversible. Element of new addition shall be identifiable and compatible with the exsiting. Cesare Brandi, an influential figure on historic conservation by the mid-century, formulated his theory of conservation based on the concept of lacuna (missing part). The reconstructed parts shall no larger in size than the original parts without the whole looking like a copy or reproduction. Seen from a distance, the intervention needs to fit into the original as a completed whole, but from close up one shall discern the necessary difference. To name an example, Parthenon in Acropolis serves a good illustration on how this philosophy applies to actual conservation work.
Fig. 9, One can also view the intervention as an ongoing process involving the conservator, the contractor and the client. The interaction among the three parties provides the information exchange that affects the outcome of work. It functions in a life cycle as opposed to the linear configuration. Therefore, one should constantly revisit different stages throughout the course of conservation work.
(8) Overall Intervention Strategy
The primary goal of repair is to restrain the process of decay without damaging effect. It is to conserve rather than restore or reconstruct. Particular attention need to pay on keeping the character of the building and the existing features that emanate the architectural as well as historic significance. The criteria for carrying out of works shall conform to the philosophy of intervention as described in section 7.
One can say the Monteath Mausoleum is in a state of accelerated erosion which requires intervention. There are in various places that column shafts being eroded to such a great extent that will constitute imminent danger to the general public and visitors. The building should be immediately fenced off from trespasses in order to prevent any mishap or accident.
As wind phenomenon plays a significant role on the material decay, the theoretic wind pattern behaviour shall be further investigated by the necessary empirical findings. In this regards, simulation of computation fluid dynamics (CFD) or wind tunnel will help to provide better understanding of wind effect on the structure. The wind tunnel is more costly option than CFD due to the need of constructing a physical model for simulation. Besides, it will take longer period to implement than computational study. Subject to finding of CFD, appropriate measure such as planting of tree as wind break shall be introduced. In Tuscany, it is a common practice to plant Italian cypress to protect church on the hill top. The pointed and pencil like form of the Mediterranean cypress provides good shelter for buildings from wind effect. Cypress also symbolizes for death and after world in the western culture. (Fig. 10)
Stone matching exercise by stone specialist will help to identify the viable source of compatible stone quarry for any conservation work in the future. With the use of X-ray Diffraction (XRD) technology, it provides crystallographic structure and mineral composition of stone. Stone matching via petrographical analysis will identify the suitable stone with similarity in appearance, mineral composition and texture, and permeability. From preliminary matching exercise by the conservation scientist from the University of Strathclyde, Drumhead will possibly be a close match to the Giffnock sandstone. One has to take caution to match the colour and surface appearance of the stone. It is good to point out that the control sample shall be the original stone of the monument itself in lieu of any other fresh sample of Giffnock sandstone. Therefore, one may need to set up matching session on the spot of the monument.
Monitoring on ground conditions and open joints over a reasonable duration will help to identify for any structural movement. Settlement gauge can be set up for ground monitoring of differential settlement. Tell-tale over gaping joints will detect for degree of movement in the structure over time. To avoid damaging the stone, tell-tale of surface mount with screw fixing is not recommended. Instead, one shall specify electronic gauge with connection to wifi that will provide the convenience in taking measurement, and serve the purpose of avoiding physical damage through mounting of devices. Plumb line will help to check the verticality of the building. As the monument is currently tilted to one direction, regular monitoring of verticality will convey the picture of differential settlement. For the underground, level of water table in soil shall be monitored through the use of piezometer.
Routine maintenance should be carried out to prevent deterioration. Plant growth needs to be stemmed from taking place. One needs to identify what species of plant growth on the building and to assess depth of root penetration for determining the removal process. Roof conditions have to be regularly inspected to prevent water ingress. Before the erection of scaffolding, roof access can be via the means of mobile platform. (Fig. 11)
Stone joints are to be re-pointed properly to prevent any unwanted moisture migration. Surface cleaning shall be performed prior to proceeding of repointing. Lime mortar shall be used for repointing in lieu of cement mortar. Cement mortar is usually not recommended on the ground of irreversible damage due to its impermeable nature and hardness which restrict thermal expansion and contraction of the existing stone material. Another issue with repointing is the choice of colour of mortar. It will affect significantly the visual appearance of the monument. To facilitate matching process, digital simulation of the mortar colour can be performed on desktop computer. Sample of works should be submitted for approval prior to the site work. Smallest joints, of a width smaller than 3mm, can be filled with lime putty. Pinning stones shall be inserted into joints, which are larger than 15mm thick [1]. After re-pointing, mortar joints are supposed to be aesthetically unobtrusive to the overall appearance.
Removal of black crust is one of the major concerns of intervention. The formation of black crust causes moisture trapping inside the stone fabric. Laser technology is considered to be the best solution. With high selectivity, it provides safe and gradual removal of the black crust without damaging the substrate. The drawback with laser is the cost implication. Laser technology is an expensive tool that requires for generous budget. Biological cleaning shall also be taken into consideration. With the procurement of sulfate reducing bacteria, it performs quite effective cleaning without involving damaging effect to the stone. On the other hand, aggressive mechanical method is not recommended. With its abrasive agent, mechanical cleaning will constitute irreversible damage to the stone. For chemical solution, one need to make sure the chemical agent is proven with long term tested records.
The mausoleum is also plagued by efflorescence and discoloration, though the extent is comparatively lesser than black crust. Removal of efflorescence shall be performed by gentle dry brushing. One of the main causes of discoloration is due to rising damp. Therefore, the provision of good drainage to surface run-off of the ground is very important. It is advisable to provide channels along the perimeter of the building at ground for collection of rainwater. Channel covers shall be made of stone pebbles on stainless steel strainer for visual integration with the monument and the surroundings.
Due to the decay of the mausoleum, it is highly recommended to have conservation structural engineer to provide expertise and to carry out structural analysis prior to any intervention. It has to review the structural integrity of the monument with respect to the stone quality, the strength, and its ground conditions. With the input of structural engineer, it can ascertain will the depth of stone decay affect the structural safety of the building. Measures and intervention shall then be formed in place on the consolidation of stone and the building with adjoining ground upon findings by the structural engineer.
On the subject of stone consolidation, in-situ conservation shall be adopted as far as possible without the removal of original pieces from the building. The cramp or dowel for fixing new pieces to existing stone should be made of non-corrosive metal. Therefore, mild steel is highly not recommended. Mild steel tends to rust easily in contact with moisture. With occurrence of rusting, the metal part will expand and disintegrate the stone fabric. Good grade of stainless steel, such as 316, is preferred for use in fixing cramp. For the case of Parthenon in Acropolis, titanium alloy was procured in for reason to ensure the fixings not to rust and fail in the long run.
Indent repair shall be performed on the defective stone pieces that need replacement. With the installation of scaffolding, a thorough inspection on the surface of the monument shall be undertaken. Joint site inspection between conservator and contractor shall be carried out to mark the defective stone that requires indent repair. But one has to bear in mind that indent repair shall only be carried out due to problem relating to structural performance.
On surface protection to arrest decay of stone, application of consolidants shall be assessed with reference to their long term tested records. For example, the organic-silicon product or ‘silanes’ that has received wide application for stone conservation. ‘Silanes’ was first appeared in stone conservation by the mid-19th century. Nevertheless, there are on the market nowadays various types of products for ‘silanes’ that require one to balance the pros and cons in their application. General speaking, the philosophy as described in section 7 shall provide the basis and principles for intervention. It is also important that the chosen consolidant will not alter any of the surface quality and appearance of the original stone material.
Dampness is the major reason that accounts for the decay of the monument. The installation of scaffolding to provide shelter will facilitate the drying process of the building. The Hill house in Helensburg designed by Mackintosh is currently protected under scaffolding for which it will sit for couple of years to let the monument dry up naturally. Due to the use of Portland cement in surface rough cast or harling during construction, Hill House had the problem of moisture trapping inside its external walls. Therefore, it is recommended to allow in the conservation works programme for the monument with problem of seepage to sit under shelter for reasonable duration prior to commencement of repair works. As Monteath Mausoleum is situated in a prominent location in Necropolis, one should pay particular attention to the aesthetic of scaffolding. The scaffolding will stay for quite a lengthy period that merits good design.
In this report, reference to the scaffold for Silver Pavilion in Kyoto is made (Fig. 16). The use of horizontal truss system that made of tubular steel will provide for long span across the monument without the need of too many vertical supports which will obstruct the view of the monument. Besides, due to its promixity to the edge of slope with very limited space on the ground for the erection of scaffolding, the truss configuration will be a good solution for the case of Monteath Mausoleum (Fig. 17). The scaffold enclosure echoes the form of mausoleum with inspiration taken from the barge project by the late italian architect, Aldo Rossi, for Venice Biennale.
Finally, the work programme shall be reviewed against the available funding. In the case of limited funding, some work items shall be put into the top priority list in the first phase of work, while the latter phases are to include the rest of the items. The urgent works include fence off the dangerous zone from trepassers, monitor of ground conditions and the open joints, remove of plant growth at roof, consolidate loosen stone pieces, and repair the collapsed rubble wall at slope. The rational behind is that the public safety shall always be the utmost concern. Any elements susceptible to falling hazard should be consolidated in-situ and addressed immediately without any delay. Besides, due to the tilting of the building, the adjoining ground conditions have to be first investigated with repair works duly taken to stabilize the building. Roof inspection and maintenance shall always precede other repair works to prevent water ingress which will be detrimental to the building fabric. We have to realize that scaffolding is an expensive installation within a conservation project. Since scaffolding is crucial to provide proper shelter for works to proceed including removal of black crust, stone consolidation and repointing for open joints, sufficient funding will need to be secured prior to proceeding with subsequent phases for the main body of works.
CONCLUSION
Upon entering, one will encounter a circular ambulatory surrounding a high and soaring central space. The screen of ambulatory forms a dark counterpart to the upper space. It is suffused with brightness, lit by lantern windows at high level. The interior is highly meditative. The space is evocative of the mausoleum of Santa Costanza in Rome which was built in the reign of Emperor Constantine during A.D. 354. Santa Costanza is regarded as a prime example of the early Christian architecture. With the facilitation by the management operator, it will be a good consideration to have the mausoleum interior open to visitors for a wholesome experience after the completion of conservation works.
Fig.22 can graphically summarize the effect to be applied to the façade of Monteath Mausoleum. The diametric contrast of the new with the old clearly illustrates the concept of ‘lacuna’. One can easily identify the new work with no disguise. This honest expression admirably aligns with the value of authenticity and integrity. In all, it sits in the orbit of minimum intervention to achieve the maximum effect.
