Restoration / Architecture · Design and Construction
Earthquake-Resistant Building · Antakya · Hatay
Stone and retaining walls
A stone wall stands by geometry, not by mortar. Batter, staggered joints, throughstones and the right hearting — these few rules decide whether a wall lasts a century or a single winter. The historic fabric of Antakya was built on them.
This page takes up two subjects together: how a stone wall is built, and how a retaining wall is set out on sloping ground. Both belong to the same craft, and both are constantly needed in Hatay.
What follows rests on public traditional walling knowledge and on our own field experience in Antakya. On where stone may be used in a new building, we convey the limit drawn by the regulations as it stands.
How does a stone wall stand?
A stone wall stands by geometry, not by mortar. Even where mortar is used, it is not the mortar that carries the wall but the way the stones sit on one another. The rules of a good stone wall are therefore the same whether it is laid dry or bedded in lime mortar.
The faces lean inwards. The wall narrows slightly as it rises — this is called batter. A wall built with vertical faces topples outwards at the least movement in the ground; a battered wall gathers its own weight inwards.
Every stone covers the joint of the two below it. Vertical joints must not line up. An aligned joint is a split dividing the wall into two independent parts.
Throughstones stitch the two faces together. At intervals, large stones spanning the full thickness of the wall are laid in. Without them the wall behaves as two separate leaves and opens along the middle — the most common cause of collapse in stone walls.
The core is filled with stone, not soil. The hearting between the two faces is made of small stones packed tightly. A soil core swells with water, heaves in frost and pushes the wall apart from within.
Each stone sits on its natural bed. Every stone is laid with its bedding planes horizontal; a stone set on edge delaminates over time. The top course is locked with a coping or capstones; a wall left unlocked at the top begins to shed stones in its first year.
Where stone walls belong in a seismic region
Honesty is needed here. Unreinforced stone masonry behaves badly in earthquakes: it is heavy, brittle and has almost no tensile strength. Because its mass is large, the earthquake force acting on it is large too. Most of the masonry buildings that collapsed in Antakya in February 2023 were of this kind.
For this reason unreinforced stone is not used in practice as the structural system of a new building in Türkiye; TBDY 2018 already sets tight limits on masonry, and stone sits at the narrowest end of them. In a new building the right place for stone is elsewhere: garden walls, retaining walls, cladding, and — within a system confined by ties — as an architectural surface.
The real domain of stone is the existing building. The historic houses of Antakya were built in stone, and conserving them, consolidating them and, where necessary, rebuilding them on documentary evidence is at the centre of our work. There the aim is not to erect a new structural system but to make an existing one safe while keeping its original technique.
One more warning: cement mortar is not used on historic stonework. Cement is harder than the stone, prevents it from breathing and accelerates salt transport — within a few years it is the stone, not the mortar, that begins to crumble. Repairs are made with lime-based mortar.
How is a historic stone wall strengthened?
In a new building you set up the structural system yourself; in a historic building you read what is there and strengthen it. The consolidation techniques used in traditional structures therefore differ from the solutions of new construction. In the conservation literature they are treated on three levels: consolidation of the material, of the structural system and of the ground.
Leaning is measured first. The rough assessment uses the “rule of thirds”: if a plumb line dropped from the centre of gravity falls within the middle third of the wall’s bearing area, the wall is considered safe; if it falls outside its footprint, there is a serious risk of collapse. Widening the section and jacketing enlarge the base area and bring the centre of gravity back within that limit.
A buttress supports, but how it bears matters. A buttress pressing on a wall at a single point is dangerous; under lateral thrust it can punch through and cause damage. A spreader is therefore used and the support distributed over a broad surface. Today, instead of permanent heavy buttresses, temporary shoring is usually erected and removed once the structure has been consolidated.
Ties and ring beams compensate for the absence of tensile strength in stone. Opposing walls are tied together; cracked vertical members are bound with metal rings. The vertical iron bars seen on the facades of historic buildings across the Mediterranean earthquake belt — called kılıç in Turkish — are the ends of those ties, pointing in some buildings to the original design and in others to a repair after a past earthquake.
Grout injection rebinds a wall whose two faces have separated. Voids and cracks within the masonry are filled with a suitable grout under controlled pressure. The compatibility of the mix with the original mortar requires laboratory work; an incompatible grout does not solve the problem but enlarges it.
The invisible solution is preferred to the visible one. Interventions that spoil the general appearance of a monument are avoided as far as possible, and techniques that can be concealed within the fabric are preferred. In practice this means that strengthening in a registered building is usually not noticeable from outside at all.
None of these techniques is chosen from a catalogue. Which one is applied is decided, once the damage and decay mapping and the structural assessment are complete, together with engineers experienced in historic masonry structures, and submitted for the approval of the Regional Conservation Board.
Retaining walls: drainage is the real issue
On the sloping terrain of Hatay, retaining walls are unavoidable. Look at retaining walls that have failed and the cause is almost always the same: water accumulated behind them. Saturated soil exerts close to twice the pressure of dry soil, far more than the wall was designed for.
The back of the wall is therefore filtered with gravel or crushed stone, a perforated drainage pipe is laid at the bottom, and weep holes are left at intervals in the face. If water drips from the weep holes the system is working; a dry weep hole is not good news — it may be blocked.
The remaining rules are the same as for any stone wall: the face is battered, the foundation sits below frost depth on firm ground, and stones are laid on their natural bed. Thickness increases with height; above a certain height an engineering calculation and a reinforced system become necessary.
Finally, two common errors: leaning a building against a retaining wall, or building on top of one. Both leave the wall carrying a load it was never meant to take. On sloping ground the right course is to seat the building on its own ground with stepped foundations and keep the retaining wall independent of it.
Frequently Asked Questions
Should I build my garden wall dry or with mortar?
Either can be right; height, ground and maintenance decide. A dry wall breathes, accommodates settlement and is easy to repair, but it demands craftsmanship and must thicken as it rises. A lime-mortared wall can be built higher. In both cases the rules are the same: batter, staggered joints, throughstones, stone hearting and a coping on top.
My old stone wall is bulging — what should I do?
A bulge usually means the two faces have begun to separate: either the throughstones are insufficient or the hearting has become mixed with soil and swells with water. Rendering over the face hides the problem rather than solving it. The right course is to document the bulging section, take it down and rebuild it with throughstones. In a registered building this work is subject to board approval.
Can we strengthen the stone walls of my registered house with reinforced concrete?
As a rule no; as an exception, sometimes. In a historic building the aim is not to erect a new structural system but to make the existing one safe while keeping its original technique, and interventions that alter the general appearance or the inner fabric of the monument are avoided as far as possible. Concealable techniques are tried first: grout injection, ties and ring beams, widening of sections, foundation strengthening. If these prove insufficient a further solution is discussed — but the justification is set out in an engineering report, and the decision belongs to the Regional Conservation Board.
Do I need an engineer for my retaining wall?
Above a certain height, yes — and that limit depends not only on height but on the type of soil retained, the water conditions and the load above. If there is a building, a road or a car park above the wall, a calculation is unavoidable. On low garden terraces the traditional rules may suffice, but drainage is required at every scale.
Sources and scope
This page rests on public traditional walling knowledge and on our own field experience in Antakya. The reference for the section on consolidation techniques in historic buildings is Zeynep Ahunbay, Tarihi Çevre Koruma ve Restorasyon, YEM Yayın, Istanbul 2009. The choice of structural system in a new building falls under TBDY 2018; above certain heights and loads, a retaining wall must be calculated by a licensed civil engineer. The text and diagrams were prepared originally by YOY Mimarlık.