Identifying the Problems and their Causes
1. Water seeping into the wall
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The seepage of water is the chief cause responsible for the deteriorating processes that are at work in the wall. Most of the problems - stone deterioration, the disintegration of bonding material, vegetation taking root, the rusting of steel parts etc - stem from water percolating into the wall. Moreover, the problems that are created in the wake of the seepage further exacerbate the percolation and bring with it a new cycle of deterioration (Fig. 1: Chart showing the development of the deterioration processes influenced by water seeping into the wall).
The problem of water seepage is mostly the result of modern intervention in the wall whereby the tops of the wall were sealed in a concave fashion which formed depressions on the horizontal surfaces, without any provision for draining the water from them.
The places through which the water seeps into the wall (Fig. 2):
- Top of the wall (tops of the crenellations and the embrasures).
- The connection between the promenade and the wall.
- The connection between the stone parapet and the promenade.
- The sentry path and the sentry posts.
- The roofs of the towers.
- The remains of the ancient buildings and the walls adjacent to the city wall.
- Cracks in the wall, especially the open cracks along horizontal planes.
- Joints devoid of bonding material.
- Faulty development or the lack of development next to the wall.
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 Top of the wall (the tops of the crenellations and the embrasures).
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The survey revealed that numerous places along the top of the wall are not protected from rainwater. A little of the original sealing which was done utilizing a lime-based bonding material, was preserved between the crenellations, particularly in shaded locations. The manner of treatment, including the materials, the finish and the state of preservation of the top of the wall, varies the length of the wall.
Hence several states of preservation, which characterize the top of the wall, were noted in the survey. Most of them were caused as a result of modern intervention that hastened the deterioration processes and destruction:
- A. The top of the wall is concave-shaped. The concave shape on the top of the wall was formed after the original sealing crumbled and a layer of modern sealing (cement) was applied to the area of the core only. This layer was applied at a level lower than that of the outer stone facade. No preparations were made for draining the water from the "bowl" that was created. Even in those places where it was planned that the water would drain via the side joints, it is evident that the method does not work: the water does not drain and consequently cracks formed, vegetation took root, the sealing itself was damaged (Fig. 3) and water seeped into the core of the wall.
In this instance it is recommended that the top of the wall be resealed in a convex manner.
- B. Just the joints are sealed on the top of the wall.This situation was caused when the original sealing was dismantled and only the joints between the stones were resealed. Cement was utilized to seal the joints. This was done at a level several centimeters lower than the top of the stones of the exterior surface so that the water would drain via the side joints. The shape of the joints forms a system of channels. The water did not drain because of differences in elevations, the channels became blocked with soil and cracks formed in the connections between the sealing and the stones (Fig. 4).
- C. Convex-shaped sealing on the core only. Most of the stones on the exterior surface at the top of the wall have an upper edge that slopes in the direction of the core. Sealing the area of the wall's core only created a seam between the sealing and the stones along a level below the top of the stones (Fig. 5). As a result of this there is no proper drainage and instead water penetrated into the cracks.
- D.Sealing is missing at the top of the wall.
In this condition, where the ancient sealing is destroyed, water seeped into the core of the wall. When the fill in the vertical joints deteriorated and was washed away, the stones at the top of the wall lost their stability and they are likely to move and even fall (Fig. 6).
In the four instances described above, it is recommended that the top of the wall be resealed in a convex manner.
- E. A stone is missing and the sealing is convex-shaped (Fig. 7).
In this situation one must be content that the place where the stone is missing is sealed.
The following three conditions describe a state whereby drainage exists but the cause of the problem lies in the material:
- F. The top of the wall is level. Level sealing at the top of the wall eliminates the phenomenon of standing water. In those places where the sealing is level the condition at the top of the wall is reasonable (Fig. 8). Despite this, it is recommended that the sealing be applied in a convex manner similar to the original sealing.
Since the repairs of lime-based materials will not be effective in close proximity to cement it is recommended that the preliminary repairs be made using sealants that are "polymer neutral" from a chemical standpoint.
- G. The top of the wall is convex-shaped. Convex-shaped sealing is the traditional specification for finishing the top of the wall. Remains of lime-based bonding material on the jambs of the embrasures between the crenellations bear witness to the fact that the sealing was done in this manner (Fig. 9). Although not much evidence remains of how the original Ottoman sealing was done, we can, based on the remains, assume that that was a finish specification at the time the wall was built. In this way it was also possible to drain the water when there were small cracks that existed in the sealing specification.
It is recommended that the top of the wall be sealed in a convex manner utilizing lime-based material.
- H. Stones missing at the top of the wall; sealing exists. Cement sealing exists on a partially destroyed top of a wall in many places on the crenellations and embrasures (Fig. 10). Nonetheless, the slopes and water drainage are reasonable.
In such instances sealing using a lime-based material is recommended. Localized repairs should be sufficient as a preliminary treatment.
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The connection between the promenade and the wall.
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On the level of the promenade the seam between the flat part of the promenade and the wall is not sealed and there is a gap that was filled with earth and vegetation (Fig. 11). The space is located above the core of the wall, which is built of soil-based rubble construction (debesh). Water seeping into the core of the wall is likely to wash away the bonding material; create lateral pressure on the outer sides of the wall; cause the stones to deteriorate which in turn will result in the wall losing its stability.
Insofar as this weak point is concerned, it is recommended that a rolka specification (a semicircular casting) be formed that will repair, as much as possible, the opposing inclination that was created by the promenade pavement. Vegetation should be removed; the gap should be filled in with an especially durable lime-based material and routine conservation maintenance should be performed.
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Stone parapets on the inside of the promenade.
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Drainage was not properly prepared in those places where a stone parapet was built on the inside of the promenade. In the absence of an outlet the water seeps into the wall and into the parapet (Fig. 12). The bonding material is subsequently washed away from the first courses of the parapet. This situation is likely to undermine the stability of the parapet followed by the stones becoming detached from the wall. The condition of the stone parapets in the fa?ade facing the city was not examined due to limited accessibility.
With regard to this weak point it is recommended that drainage be prepared in the vicinity of the stone parapet which disrupts any possibility of drainage; vegetation be removed, the existing gap be filled with an especially durable lime-based material; and that routine conservation maintenance be conducted.
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The sentry path and the sentry posts.
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The upper level of the sentry path is not sealed; soil has accumulated on it and a rich assortment of vegetation has developed along most of it (Fig. 13). The rainwater percolates through the sentry path into the core of the wall and thus washes the bonding material from the core and destroys the stones on the side that faces the city. The water also seeps from the path to the sentry posts, via the firing slits and flows along the fa?ade. As a result of this the stones in the vaults of the sentry posts, in the fa?ade of the wall and in the firing slits are deteriorating and vegetation is growing in the joints of the stonework.
It is recommended that special attention be paid to seal the walking surfaces and sentry posts; that vegetation be removed, drainage prepared and that routine conservation maintenance be performed.
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The roofs of the towers.
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The sealing on the roofs of the towers is damaged and water therefore seeps into the walls and vaults, and vegetation is taking root on the roofs (Fig. 14).
It is recommended that the damaged pavement on the roofs of the towers be repaired; that the tops of the walls of the towers be sealed and that conservation maintenance be implemented.
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Remains of ancient walls and buildings that are adjacent to the city wall.
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The remains of the ancient city walls on which the existing wall is built have been neglected. The horizontal surfaces are not sealed and water seeps through them into the wall (Fig. 15). The remains were covered with vegetation. This is a detrimental situation that endangers the ancient remains and the wall that was built alongside them or on top of them.
Insofar as this problem is concerned, it is recommended that the upper surfaces of the remains adjacent to the wall be sealed and that conservation measures be carried out on the remains of the ancient walls.
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Cracks in the walls, particularly cracks which have opened in horizontal surfaces
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See Problem 4 - Cracks
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Open joints
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See Problem 3 - Deteriorating bonding material
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Development or the absence of development and the maintenance next to the wall.
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The survey has pointed out four destructive factors that are the result of faulty development or the absence of development and maintenance:
- Opposing incline. In the regions where the area next to the wall was not developed there is often an incline that slopes in the direction of the wall. As a result of this water that is standing next to the wall is absorbed into the foundations and capillary action draws it up into the wall. This situation promotes destructive processes in the wall.
- Drainage flowing in the direction of the wall. In certain areas the drainage of rainwater next to the wall was arranged in such a manner so as to cause damage to the wall. In most of places where drainage was prepared in recent years the water flows in the direction of the wall, along the wall or through perforations in the wall. There are cracks in the channels that run the length of the wall through which the water seeps into the wall (Fig. 16: development without proper drainage). Improper drainage of the parking level located on the inside of the wall has resulted in vegetation taking root in the lower part of the wall's outer surface.
- Gaps in development. Unsealed gaps exist between the pavements that were installed next to the wall and the wall itself. The spaces create a place for vegetation to take root and allow water to be absorbed into the wall.
- Landscape development.
The development of the wall promenade included the planting of trees and lawns next to the wall. The irrigation of these plants is a source of water that is absorbed into the wall. Moreover, the roots of the trees damage the building material.
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2. Stone Deterioration
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