| The Old City of Akko (Acre) |
| The Hospitaller Center |
| Conservation measures undertaken in Hall of Pillars (“Grand Munir”) |
| Orderer | Old Akko Development Company, Ltd. |
| Duration | 2003 |
| Address | Block: 18009, Lot: 2 |
| Implemented by: |
Yotam Carmel
Orit Soffer
Vadim Zaytlin
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The purpose of the conservation measures undertaken in the Hall of Pillars was to resume the process of physical and structural stabilization of the hall while at the same time restore its architectural features which were severely damaged over the course of history and/or by previous conservation steps that were carried out.
The first restorations in the Hall of Pillars were done in the 1970’s, after the hall was partially exposed. The restorations that were conducted at that time were done so without documentation and without studying the original Crusader building methods. The materials that were used were, for the most part, unsuitable (such as cement based bonding materials) and the masonry stones used did not take into account the size of the original stone courses.
From the beginning of the fortress conservation program by the Antiquities Authority, extensive conservation and restoration steps were carried out in most parts of the hall, save the southeastern corner where the excavations were only completed at the beginning of 2003. In the initial phase the work included engineering reinforcements – pouring concrete pilings, restoring elements that collapsed with concrete and supporting pillars with steel bands. In the second phase the vaults and pillars were strengthened by means of grouting and the conservation of the stone’s surface. Finally in those places where it was necessary to restore the structural function of the pillar, complete restorations were made using sawed and dressed stone while allowing for the dimensions of the original courses. The walls of the hall and the pillars, which fulfill a structural function, underwent minimal treatment only aimed at preserving their current condition (without restorations).
Decisions regarding the nature of the conservation intervention were guided by the following criteria:
1. Addressing structural problems: Where structural problems existed due to missing stones, the stone work was completed in order to stabilize the wall.
2. Maintaining uniformity with previous undertaken conservation measures: It was decided early on in the work that no restorations and supplemental work would be carried out that were not structurally necessary and only minimal conservation treatment was done to maintain the current conditions (joints were pointed up, inner cavities were filled with stone, grouting).
3. Conservation of elements that document historical processes.
4. Climatic conditions (humidity and high levels of salt): The materials were selected in accordance with the climatic conditions in the structure. No use whatsoever was made of any organic materials in order prevent the development of biological nuisances in the future.
The Treatment to the Vaults (A)
Vaults I and P were found cracked and have shifted as a result of the loads they bear. Vault I (between Pillars 9, 10, 11, 12) was strengthened and grouted early on and was in a better condition than Vault P to its south (Pillars 11, 12, 19, 20).
The following problems were readily apparent in the vaults: the detachment of the outer layer of the vault’s stones (This problem is characteristic of all of the vaults in the hall. It probably stems from mechanical tension: cracks, weathering and deterioration of the surface of the stone); empty spaces inside the stones (an early stage before the detachment of the outer stone surface) and detached remains of the original plaster. The conservation measures we performed included: installing instrumentation to measure cracks, grouting – injecting pit lime and hydraulic lime based liquid bonding materials into the inner cavities between the stones and behind them; pointing up the joints and reinforcing the stones with fiberglass pins.
The Treatment to the Wall in the “Beautiful Hall” (B)
When the vaults were built in the Hall of Pillars, a recess, in the shape of an arch and c.12 cm deep, was roughly chiseled in the façade of the “beautiful hall”. This was done so that the wall would conform to the shape of the vault. This measure caused massive mechanical damage to the stone. Today we can clearly discern between the recessed area and the original surface of the stone. The difference in the state of preservation between the side of the wall that faces the “beautiful hall” and the deep weathering in the façade facing the Hall of Pillars is a fascinating example and important evidence of the construction process of the fortress. The difference is particularly evident in the region of the window connecting the two halls.
The nature of the conservation intervention in the wall was determined with the aim of preserving the traces of the mechanical damage that was caused to the stones in the vicinity of the recess.
This wall was characterized by spaces between the stones and behind them (mainly in the region of the window), missing stones, joints that were devoid of bonding material and the natural weathering of all the stones. Deep weathering is evident in the stones located in the vicinity of the recess as compared with the stones of the original surface. The state of preservation of the arched window in the area was particularly problematic. There is a significant difference in its condition on either side of the wall. From the side of the “beautiful hall” the window was unblemished and from the side of the Hall of Pillars its condition was bad from both a structural and visual standpoint. The voussoirs on the side facing the Hall of Pillars suffered from advanced weathering (c. 50% of the stone mass was missing) and there was almost no bonding material between the stones. The arch, which was detached and no longer secured to the wall, was not fulfilling its structural function.
The conservation measures that were taken consisted of: injecting pit lime and hydraulic lime based liquid bonding materials into the inner cavities between the stones (grouting), replacing missing stones, pointing up the joints and filling the inner cavities with stones, completing the stone work in the window frame so as to restore it to its structural function.
The Treatment to Pillar 16 (C)
The upper part of the pillar and the bottom part of the vault’s ribs were partially restored during the 1970’s. The restoration was done with small stones, utilizing cement based bonding material and without taking into account the original stone courses. At the beginning of 2003, the first three courses of the pillar were reconstructed again. During further treatment two additional courses were added including a stone seat for the cornice. The stones for the cornice were dressed by hand, using tools and techniques that closely approximate Crusader stone dressing.
The conservation measures that were carried out in the locations mentioned above have not been completed and they will continue during the current work year.
To view the figures, click on the figure caption
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