The desire to repair and conserve structures is very different in different cultures. Buildings constructed by the first European settlers in the United States, Australia and New Zealand are now national historic
monuments, whereas buildings of the same age in Europe barely receive a second glance. European and other ‘Western’ views of the conservation of historic sites are perhaps the most stringent, aiming at rehabilitation to conserve cultural integrity, rather
than restoring a structure to return it to its original condition and function. In this philosophy it may be considered better to turn a historic site into a museum than to return it to a functioning property.
By contrast, Eastern philosophies tend to champion renewal, meaning that religious buildings constructed in the previous year are of equal importance to those constructed in previous centuries. Here a philosophy of replacing old with new is considered perfectly acceptable, and conservation strategies need to reflect this attitude.
International documents, such as the ICOMOS Venice and Burra charters, set standards for
practices and strategies to be followed in conserving historic monuments. Although such charters are very broad, they offer principles that should be adhered to in the conservation of historic buildings, and which should be applied to earth buildings.
The charters advocate a cautious approach to repair, and a practice of minimum intervention:
‘to do as much as is necessary but as little as possible’, to care for and to maintain a site, such that the cultural significance is retained. A high value is attributed to the cultural significance of the structure, the construction materials, and the fixtures of a building. The conservation process is viewed as one of change, where change reduces the cultural significance of a site. Any intervention should be clearly visible and reversible, so that if improved methods become available in the future, it is possible to implement them without causing damage to the structure. When a site is being
conserved, the charters call for a detailed assessment of the reasons for deterioration and the production of a well-defined conservation policy. The process of conservation should be clearly documented, to ensure that the site does not deteriorate further, and a maintenance and monitoring regime should be implemented.
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5.3
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EARTH-BUILDING ANALYSIS AND REPAIR STRATEGYA suggested strategy for assessment of earth
structures is given below. The primary concern during implementation is for the safety of the workers
involved. The structure’s stability should first be assessed by an engineer, and the structure made safe through temporary works such as propping. When a building is deemed safe to enter, a full survey such as
that shown in Figure 5.1 should be undertaken. This survey should note construction materials, the phases of construction, and any demolition or reconstruction that may have taken place. Evidence of previous damage and repairs should be noted, to provide clues to causes of current damage. Different damage types occurring to an earth building are likely to be linked, and repair strategies should not be carried out in isolation.
Dateunknown
Brick structure on the site of the current building.
Arch acts as entrance to current courtyard.
Remains of further arch at the north of site at base of current gable end.
Date unkno wn
Rammed earth building to south of site.
Stream running north of this building.
Only remaining rammed earth block
Date unknown
Stone building constructed above foundations of previous stone building. Stone possibly used as base for rammed earth structure.
Building extends to current stairs to south.
Brick arch filled.
13th century
Previous stone/rammed earth building collapses/removed. Build new rammed earth and brick building.
Large rammed earth formwork used.
Possible roofline still visible within formwork.
Tower constructed at south of site, access at ground floor level.
Figure 5.1: Example building phase and cracking plan. Convento de San Juan, Ambel, Zaragoza, Spain
CONSERVATION STRATEGIES 55
Before 1536
Construction of major face. Similar to the rest of the north west.
Gable end constructed vertically above outward leaning base.
North section may have been higher.
Date inscribed on column at ground floor.
Before 1796
1st floor collapse, likely due to overloading of floor when used as a granary.
May exacerbate central cracking, causes 1st floor to fail. Removal of north section of tower (change in roofline).
Af ter 1796
Continued lean of gable end causes alarm.
Placement of timber beams tying the gable end to the perpendicular walls at the roof and 1st floor level.
Reconstruction of the ceiling arches at the 1st, ground and basement levels. Reuse of timbers at the basement and 1st floor, additional timbers placed at arch crowns at ground floor.
Cracking of floor at 1st and ground level, suggesting differential settlement of gable end.
Possibly reconstruction of the roof.
Af ter 1536
Cracking in centre of wall, likely caused by differential settlement of north section of wall.
Continual rebuilding of north section of this wall indicates settlement problems.
Diversion of watercourse may have led to change in groundwater distribution.
1796
Repair of 1st floor collapse, installation of octagonal columns on ground floor, reconstruction of 1st floor level floor. Possible construction of of basement columns.
1st floor columns not placed above basement columns.
Removal of 13th century tower.
Removal of north section of tower.
Construction of windows in central section.
2000
Continued movement of gable end.
Placement of H bars, placed at the face of the rammed earth, and bolted to the ceiling beams.
Figure 5.1: Continued
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Figure 5.2: Earth mixing and preparation area. Asslim, Morocco
Once a building has been made structurally safe, attention should be focused on arresting the reasons for the damage. Many of the issues relating to earth buildings involve water, so drainage,
evaporation and water retention issues should be addressed first. Significant repairs such as crack stitching and face filling should then be attempted.
Finally, the heads of the walls and the wall faces should be repaired to ensure that rainfall does not damage the structure further.
Suitable earthen materials should be identified for the repair. Local knowledge should be tapped to understand sources of material, and samples from these sites may need to be compared with the historic material. Areas should be set aside for mixing and preparing soil (Figure 5.2), and for producing and drying earth bricks if needed.
Once the primary conservation works have been completed, a conservation strategy and plan should be developed and implemented for the lifetime of the structure.