corbelled walls

8/22/2019 Corbelled Walls

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This project is financ ed by the MEDA pro gramme of the Europea nUn ion. The opinions expr essed in the pres ent doc ument do not nec es sarily reflect the pos ition of the Europe anU nion or of its member States 1/5

PRÉSENTATION

Geogr aphical In f luence

Definit ion

Corbelled Vault

- Dry stone vault, g enerally carried out wit hout formwork or for mw ork supports.

- The span is li mi ted and cross ed by meansof a succession of supports overhanging oneanother, creati ng the corbelling. Each row overlaps the previ ous: balance is found on

the tail stones .

- The stones are laid horizontally, or slightly

tilted outwards to run r ain off.

Environment

Its presence is li mited to three M edit erranean countries: France, Spain and Greece.

This structure is gener ally used in r ural environment.

Associated Floors:Corbelled vaults are only used on gr ound fl oors, never for upper floors.

In Spain , corbelled vaults are found in rural environment; its presence is exceptional.

I l lust rat ions

Plans and secti ons:

Spain

BuildingTechniques :

Country :

C7 – Corbelled vault



C7 Spa in – Corbe l led vau l t


CON STRUC TION PRINCIPLE

Mater ia ls

Nature and Availability (in what form)For corbelled vault constructions, the most used materials in all countries are limestone and earth. Other kinds of stones are also used according to local availability (schist and granite.. .)

In Spain, the material used for corbelled vaults is stone.

Modules, dimensions, dose ratioThe corbelled vault is a dry stone masonry: modules are stacked one on the other, l aid horizontally, or even slightly tilted outwards to prevent rainwater from entering. The ratiobetween the size of the building and the stones must be respected: the width must enable

proper crossing and the length mus t enable a deep anchoring in the mass of the cons truction.During the preparation of the work site, it is necessary t o sort s tones and classify them by thickness. Since there is no bi nding material to fill the holes, the dry stone construction ruleconsists in seeki ng the best support for each stone on the l ower element: it is a slow care ful work of observation, to think ahead and find the best possible interlockings. Small stones can

be wedged i nto the finis hed wall to lock it better still.

In Spain, the corbelle d vault is carr ied out with the flattest stones possibl e, collected byfarmers at the time of ploughing.

Type of lay ing

Type of laying, Use of a formwork, formwork supportsThe asse mbly of a corbelled vault is generally carr ied out without use of a for mw ork. Thelaying of the s tones is started from the key, balancing the loads on both side axis of the vault.It results from the superposition of the various rows of stones which close up as theconstruction advances. Each row overlaps the previous one, hardly more than its own

thickness, except for the very last r ows: thus, balance is obtained at the tail of the stones.The stones are carefully crossed, rows become interdependent. The two vault heads would collapse one against the other if the builder did not balance them by loading the tails.

In Spain, the vault is carried out without formwor k or formwork supports.

Too ls

In addition to the traditional mason tools, no particular tool is necessary f or the implementationof corbelled vaults throughout the studied countries.

Trades

Trade, Number of people necessaryCorbelled vault is generally an is olated construction linked to agricult ural and farm activities , it is thus often carried out by a mason or private individuals (us ers).

In Spain and France, the corbelled vault is carried out b y a mason or far mers usi ng thematerials available on the site.

Performances

Physical (span...).This constr uction technique results i n a crossing of spans which extend from 1 to 3 meters for a thickness of about 40 cm.

Thermal - Acoustic.This constr uction technique has average ther mal and acoustic perfor mances, as reported by the s tudi ed countries

Waterproofing, protection against bad weather (top floor)In the auxiliary agricultural constructions, this vault i s covered by an earth layer, progressiv ely

colonised by vegetation, and which ensures a relatively good w aterpr oofing.

I l lust rat ions

Construction principle - type of l aying :Vertical section, sche matic plans




This pr oject is financ ed by the MEDA pro gramme of the Europe anU nion. The opinions expr essed in the pres ent doc ument do not nec es sarily reflect the pos ition of the Europe anU nion or of its member States 3/5

ASPECT, PATHOLOGY

Aspect

Finishing, associated roofing.Corbelled vaults are generally le ft bare

In Spain and Greece, in certain areas, corbelled vaults are covered with special clay or render ed with clay mort ar.

Agei ng pathology

Linked to materials and climatic conditions :It is important to note that direct erosion wears the materials, especially in the case of corbelled vaults which only provide average roof pr otection: waterproofing not being their main quality.

In Spain, vaults can suffer from pathological problems when built with sandy stones whichundergo decalcification.

Linked to the technique:The non-observance of the fundamental construction r ules for dry stone walls is the source of most problems: chain reaction sliding if a stone is poorly laid, problems linked to thr ust of

overhanging materials.No specific pathology linked to ageing in this construction technique were reported b y Spai n

and France.

ASSOCIATED WORKS

O en in s

Small openings are p ossible on w all level to ventilate the rooms or to give light. Narrow and small in all types of dry st one housi ngs, they of ten inform us on the key use for the builder

(herd, crops, game, landscape...).

Connection framework - Vert ical Structure (wall ) :No type of connec tion was reported: the vault is assembled in the continuity of the walls, at the same time and by the sa me people. The two works are link ed.

I l lust rat ions

Construction principle :sections and schematic plan





REALI ZATION D ESCRIPTION

In Spain :

PREREQUISITESThese are isol ated constructions r elated to agricultural work, built using t he stones removed from the soil when i t is ploughed. I t is the farmersthemselves who build these huts using the materials available. T he roof of the hut is a vault built by compression, as it is co nstructed in courses,

not arch bricks, unti l it is covered in.

Materials:Stones whic h are as flat as possible, normall y limestone. They are often found under an initial la yer of topsoil. Before starting construction, thefarmer cl ears the ground to remove stones, piling them up on the site where he i ntends to build the hut.

Clay

ToolsVery few tools are used, as they would have to be taken to the site of building, which could be some distance away.Hammer

Mortar troughPicks and shovels to clear the ground

STARTING W ORK- Laying out the ground plan of the hut.

- Construction of the walls using large stones. The walls tend not to be very high, as the vault begins quite l ow down. The usual height of the

walls is between 035/040 m and 1.50 m at the highest.- Construction of the portal in the form of an arch or with stone jambs and lintels.- The construction of the vault begins wit h flat stones , as large as possible. The stones are laid i n courses. Each course advances a li ttle over the

last until the vault is closed.

- The stones in the vault are wedged together to rei nforce the circular courses.- The stones tilt slig htly so that rainwater runs outwards off them.- Closing the vault. The s ystem used to close the vault does not always involve a key; this depends on the place. Sometimes the s tones are

placed on edge, to act as a key, in other c ases the vault is closed in courses, and another sol ution is the use of a flat stone.- The extrados of the vault is filled in with rubble and small stones to form a mound.

- In some areas, the outside of the roof is covered wit h earth.- Infrequently, the inside is rendered with cl ay mortar.

OBSERVATIONSIf the plan is square, construction invol ves squinches, whic h take many different forms.

In areas where there is plenty of regular-sized stone, we find barrel vaults built with arch bricks of varying regularit y.





USE, EVOLUTION AND TRANSFORMATION

U se

Types of buildingsCorbelled vaults are exclusively used for the construction of the annexes for far ms , sheep-folds, shepherd shelt ers (bories.. .) Found especially in

places where li mestone is broken or split i nto thin stones and plates.In Spain , these constructions ar e isolated constructions, lin ked to farm activities.

Period when the technique first appeared. Period when the technique is in use – still used today or disappeared :This technique of construction is prior to Antiquity. It is disappearing except for Greece where its use remains in cert ain areas.

Reasons why the technique disappeared or has been modified :The reasons evoked by all countries are mainly the slowness of work and the regressi on of the know-how linked to this technique.

Evolut ion / Transformation

The materialsNo evol ution, nor transfor mation. When the corbelling vault is s till built, the technique used remains identical to the original one, secular.Respectful to the si mplicity of the ancestral model, it is always directly related to t he immediate proximi ty of the materials necessary for i tsconstruction (stones).

The technical aspectsNo evol ution, neither transformation.

Evaluation of materials and replacement techniquesNo obj et.

corbelled walls

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