Restoration / Architecture · Design and Construction
Guide · YOY Mimarlık
Why do historic buildings decay?
Before repairing a historic building there is one question that has to be answered: what caused this damage? Repair carried out without removing the cause wastes both the money and the effort spent on it. This guide sets out how the conservation literature classifies the causes of decay, and how they appear in Antakya.
Diagnosis first, treatment second
A comparison often used in the conservation literature runs like this: the architect who is to carry out a restoration works like a physician facing a patient who can only describe himself through his symptoms. The building is observed at different times — in the heat of summer, in the rain, under snow — and the cracking, efflorescence and moss growth are recorded together with the agent that caused them.
The practical consequence is clear. If the cause of damage is not removed, the decay continues; the time, effort and money spent are wasted. Worse, the damage grows during the delay and new problems appear. Re-rendering a wall whose plaster has fallen away is not a repair but a postponement, unless the damp that pushed the plaster off has been cut.
The causes of decay are examined in two groups: internal causes, arising from the building itself — its position, design, materials and workmanship — and external causes, arising from nature, disaster and human action.
Internal causes: position and ground
Where a building stands determines directly how much it will suffer from the climate. A building at the foot of a slope or in a hollow, where surface water is not properly collected, stands in water for long periods after heavy rain; its timber doors rot, and decay begins in its floors and the lower courses of its walls.
Ground of low bearing capacity, or ground that is not homogeneous, produces visible damage over time in the form of rotation and differential settlement. Made ground is particularly prone to this. The position and direction of the cracks in a building give a rough indication of whether the damage originates in the ground — but firm diagnosis belongs to geotechnical engineering.
A building standing on a fault line, or on rock with fissures in its formation, also carries a raised risk of loss. Antakya falls squarely within that description; the relationship between ground and fault in the city centre is on its own the single most decisive component of the damage picture.
Internal causes: design, material, workmanship
Errors of sizing carried over from the original design produce serious damage. A wall too thin for the load it carries eventually bulges; where buttressing is inadequate, arches, vaults or domes spread and the system can collapse. Foundations that are weak or of insufficient section likewise cause cracking and leaning above.
The quality of the material determines the lifespan directly. Clay seams within a stone lead to rapid erosion. Sedimentary stones lie in horizontal beds in nature; if a block is cut and set against its bedding, the decay takes the form of layers spalling off from the face inwards. Poorly fired brick shows rapid erosion, loss and pitting. In masonry, the quality of the mortar binding the material is at least as decisive as the stone itself: in a wall laid in mud or weak lime mortar, the building disintegrates as the mortar dissolves.
Poor workmanship and wrong detailing waste good material. Where the iron cramps and dowels joining ashlar blocks are not properly insulated, water penetrating the joints rusts them; the metal expands as it corrodes and the internal stress cracks the stone, and if nothing is done the architectural element breaks up. The remedy is usually to change the material: replacing iron dowels and cramps with stainless steel or titanium.
In regions of heavy rainfall, a flat roof is itself an error of original design: waterproofing is hard to maintain, condensation causes decay, and it demands constant upkeep.
External causes: the long action of nature
Buildings weather under nature’s various actions over long years, and without continuous maintenance the damage becomes serious. Material that expands in summer heat is exposed to frost in winter; temperature differentials and freeze–thaw cycles fatigue it.
Water is on its own the greatest agent. Damp rising from the ground by capillary action wets the structure, adds to the load on the load-bearing elements, and produces efflorescence as the salts it carries crystallise on the wall face. In a building whose roof covering or gutters have failed, rainwater cannot be carried away quickly; moss takes hold and fungus develops in timber roofs and floors.
Water that enters cracks and freezes acts as a wedge; the crack widens and large pieces break off. In Ottoman buildings, where the grille sockets at the foot of window jambs are not filled with lead, water entering those voids freezes in winter and splits off part of the jamb. Rainwater running over the surface erodes it: when the lower part of a building is undercut, the sections above are left cantilevered and, unsupported, break away.
Seeds carried by the wind and lodged in joints and wall cavities germinate; fig and tree-of-heaven take root on the facades and roofs of neglected buildings. Birds puncture lead roofing and let water in, wood-boring insects eat timber from within, and lichens and micro-organisms accelerate the decay of stone. What all of these have in common is this: they begin as small damage that continuous maintenance can put right.
External causes: disaster and human action
Disasters such as earthquake, landslide, flood and fire strike suddenly and call for large-scale intervention. In Turkey, which lies on an earthquake belt, monuments have been damaged, destroyed and rebuilt by tremors throughout history; the traces of post-earthquake repairs can be read in many important buildings. The ties and anchor plates seen on facades are often the record of exactly such a repair.
Among human causes, abandonment comes first. The emptying of a historic settlement and the neglect of its fabric usually rest on social and economic causes: when the original owners move to the newer districts of the city, the old houses become rented lodgings and deteriorate rapidly. Some buildings are deliberately left to their fate by owners hoping that they will fall down and can be replaced.
Poor use accelerates ruin. Mezzanines, partition walls, shopfronts cut into the street elevation and separate entrances added at the wish of new occupants transform a building quickly. Some of these damage not only the appearance but the structure: cutting the posts and rails of a timber frame in order to widen a window in a traditional house directly injures the structural continuity.
Poor repair is the most insidious, because it is done in good faith. Repair is specialist work; repairs not carried out by properly trained architects and craftsmen, with suitable materials and techniques, amount to little more than patching, and usually leave irreversible loss behind. The case we meet most often in Antakya is the use of cement mortar in stone walls built with traditional lime mortar: a hard, impermeable mortar forces the soft stone to its own advantage and accelerates the decay.
Frequently Asked Questions
Can I tell the cause from the cracks?
A rough reading is possible. Where a building bears on firm ground at both ends and the ground in between is loose, cracks appear on the elevation starting at the corners of door and window openings and running outwards at roughly 45 degrees. Where firm ground lies only beneath the middle, the cracks widen from the bottom upwards. This is only a preliminary reading, however; firm diagnosis and remedy are the work of geotechnical and structural engineers.
How do I know whether a crack is still moving?
To find out whether a crack is live, a glass tell-tale is fixed across it — if the glass breaks, there is movement. For finer monitoring, the crack width is measured and logged at regular intervals with a crack monitor or a Demec/strain gauge. To see the condition of the wall behind a surface crack, the render may have to be cut back over a limited area; that too requires permission.
Can I cover salt efflorescence with paint?
No. Efflorescence is not surface dirt but the point at which water and salts inside the wall are emerging. Sealing the face with an impermeable paint or render pushes the evaporation deeper into the wall; the salt then crystallises beneath the render and pushes it off from within. The correct sequence is to cut the source of the damp first — rising damp, a leak, a failed gutter — and only then repair the surface with a breathable material.
What is the cheapest form of conservation?
Continuous maintenance. That is the underlying approach in conservation today: in many countries historic buildings are inspected under annual and five-year programmes and the damage found is dealt with while it is still small, so that they are preserved without any need for costly intervention. A few tiles replaced in time, a gutter cleared in time, bear no comparison with the cost of the roof and floor repairs that would otherwise be needed years later.
Source
The principal reference for the classification and technical definitions in this guide is Zeynep Ahunbay, Tarihi Çevre Koruma ve Restorasyon (Historic Environment Conservation and Restoration), YEM Yayın, Istanbul 2009, Chapter 3: Agents of decay in monuments. The observations and assessments concerning Antakya rest on YOY Mimarlık’s own fieldwork.