Adobe and Timber

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Adobe and Timber Ties as MainConstruction Materials for an HistoricGreek DwellingAnna-Maria Vissilia a & Maria Villi ba National Technical University of Athens, Athens, Greeceb Private Practice, Athens, Greece

Available online: 11 Jun 2010

To cite this article: Anna-Maria Vissilia & Maria Villi (2010): Adobe and Timber Ties as MainConstruction Materials for an Historic Greek Dwelling, International Journal of Architectural Heritage:Conservation, Analysis, and Restoration, 4:4, 295-319

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ADOBE AND TIMBER TIES AS MAIN CONSTRUCTIONMATERIALS FOR AN HISTORIC GREEK DWELLING

Anna-Maria Vissilia1and Maria Villi

2

1National Technical University of Athens, Athens, Greece2Private Practice, Athens, Greece

This article examines a composite construction system concerning a Greek historic dwelling.

Various aspects of current proposed interventions are discussed illustrating the subsequent

restoration based on the architectural and structural analysis of the dwelling and its con-

struction methods and building materials, as well as on laboratory tests on the properties of

its main construction material, the adobe (mud bricks). In addition, the main causes of the

current weathering of the dwelling are reviewed, with primary focus on the various mechan-

isms that affect the load-bearing walls of adobe bricks, a local construction material that

endured the climatic condition of the region and kept the building extant for more than 100

years. The restoration–reuse proposal aims to integrate the dwelling in contemporary life

through appropriate interventions so that its architectural, typological, functional, and

constructional characteristics will be preserved, based on an internationally accepted frame-

work of principles regarding historic architecture.

KEYWORDS: historic architecture, restoration, structure, adobe (mud brick), timber ties

1. INTRODUCTION

The historic buildings of Itea, a city of 3,000 inhabitants located in mainlandGreece, date back to the second half of the nineteenth century. They evolved slowlythrough time, responding successfully to the climate through the appropriate selectionof construction techniques and materials. Our case study building reflects the sameprinciples of construction and design since it belongs to the historic architecture ofItea.

The existence of the historic architecture in Itea is under threat in recent years.Historic dwellings are disappearing rapidly since adobe is now considered inadequatefor structural use, in contradiction to the old saying ‘‘I promise to protect you fromearthquakes on the condition you protect me from rain’’. The abandonment ofhistoric building methods and materials took place around 1945 due to extensive useof reinforced concrete versus masonry, a construction material of significantly higherresistance and reliability. Although such buildings are usually not designed to con-form to the texture of the architecture and the climatic conditions of the region, livingin them has been considered by the local people as an indication of status. This fact ledto the deterioration of the historic architectural texture of the city, and a significantnumber of the historic buildings of Itea are facing oblivion.

International Journal of Architectural Heritage, 4: 295–319, 2010

Copyright # Taylor & Francis Group, LLC

ISSN: 1558-3058 print / 1558-3066 online

DOI: 10.1080/15583050902934973

Address correspondence to Anna-Mari‘ Vissilia, Department of Structural Engineering, National

Technical University of Athens, Kodrou 13, 105-58 Athens, Greece. E-mail: [email protected]

Received 16 March 2009; accepted 31 March 2009.

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Therefore, rehabilitation strategies for the remaining fragments of the historicheritage of Itea, aiming at ‘‘sustaining’’ their essential qualities while adapting them tonew conditions and needs, may contribute to the strengthening of local culturaltraditions and forms. The economic aspects concerning rehabilitation and revitaliza-tion schemes are also important. It is interesting to point out that experience in manycountries has shown that it may be easier and less costly to restore historic buildingsthan it was originally thought. In contrast, the cost of demolition and replacement bynew buildings has almost always turned out to be more expensive than expected(Steinberg 1996). Historic buildings are important components of city life and it iscrucial that political support be generously offered for such substantial rehabilitationand revitalization schemes. It can then be argued that proposals of appropriatemethods for intervention and reuse can help in strengthening the argument towardspreservation.

This article comprises a historical review of the building, an analysis of itsarchitecture, a discussion of its structural system, and of the strength and durabilityof its materials (including laboratory tests), a presentation of the current state of thebuilding, and finally, the philosophy of its restoration.

2. ARCHITECTURAL–STRUCTURAL ANALYSIS AND DOCUMENTATION

The protection of the architectural heritage has been a subject of numerousdiscussions in Greece in recent years. Nevertheless quite often, current restorationpractices seem to be preoccupied with issues of appearance rather than with an indepth study and understanding of the buildings form and their relation to structureand construction materials. The authors of this article maintain that, before formulat-ing appropriate restoration concepts, it is important to study a historic constructionby researching its typology and architectural character, investigating the qualities ofthe building materials and the history of the structure, and documentation the currentdamages and their causes.

This study includes an architectural analysis (typological and morphological) ofthe building, a discussion of its structural system, construction materials and techni-ques, laboratory tests concerning its main building material. It also comprises acollection of data (photographs, drawings, old photographs, and interviews), biblio-graphic research, as well as description and assessment of current damages and theircauses, and finally the proposed methodology for restoration and reuse.

2.1. Historic Use, Occupancy Patterns and Typology

The historic dwelling of the case study is a two-story nineteenth-century buildinglocated on the front district of the city of Itea, which adjoins the sea. It is a represen-tative example of the neoclassic type of houses incorporating, at the same time,vernacular elements of the traditional architecture of the area, as they were typifiedat the nineteenth century (Figure 1) (Kolokotroni andYoung 1990). It was built in twophases: the first part of the dwelling was built in 1876, being one of the first housesafter the major earthquake of 1870, and the second part was added in 1890.

The first part of the dwelling, constructed in 1876, consistedmainly of a compactbuilding form of a square plan layout of 10m and an extensive garden, incorporated inits typological layout, which allowed flexibility of use according to climatic

296 A.-M. VISSILIA AND M. VILLI

INTERNATIONAL JOURNAL OF ARCHITECTURAL HERITAGE 4(4): 295–319

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conditions. It was developed in two stories: the ground floor was used as a workingplace for agricultural purposes and storage, and the upper floor was divided into fourrooms organized around a central corridor of relatively small size. An interior woodenstaircase unified the two floors of the residence. The two rooms placed on the south sidewere occasionally unified and functioned as themain living room, the so-called sala of arather large size. The other two, placed symmetrically on the east and west side of thecorridor, were used as bedrooms. A main fireplace was situated on the western outerwall of the main living room, which was used for cooking and heating. Indoor bath-room facilities, as well as a separate kitchen were not yet available (Figure 2).

In 1890, the original square plan layout of the dwelling was transformed to arectangular layout (10 X 15 m). The spatial arrangement remained conventional.

Figure 1. Illustration of the general view of Itea circa 1910 (figure is provided in color online).

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KITCHENOVENSTORAGE ROOM

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PLAN OF THE GROUND FLOOR

STORAGE ROOM

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Figure 2. Plan of the ground floor (figure is provided in color online).

ADOBE AND TIMBER TIES 297


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Another wooden staircase leading to the ground floor, a central corridor and threedistinct rooms set around it, one of which was used as the kitchen, were added. Theground floor was still used for agricultural storage where olives and olive oil were keptin kegs along with other food items and household objects. A one-storey orthogonalbuilding was also added to the main house on its north side. This additional buildingwas used to cover further agricultural needs, as well as additional cooking and laundryfacilities. Finally, a small room was located in the garden away from the main livingunits, which was used as the bathroom of the dwelling (Figure 3).

2.2. Construction Materials and Techniques

The method of construction of this historic dwelling is highly place-specific: theconstruction system was based on the availability of local materials and on technicalmethods responding to local constrains, empirical knowledge, and professional mas-tery (Givoni 1998). The building form was conditioned by its structure and articula-tion of construction details, which, in the opinion of the authors of this article are basicfactors for bringing architecture to realization.

The building, being constructed in an earthquake-prone area, had sufferednumerous earthquakes (e.g., a few major earthquakes: Atalante in 1894, Alkyonidesin 1981, Kalamata in 1986, Aigio in 1995, Athens in 1999), as well as erosion due to itsproximity to the sea. It is important to note that the dwelling managed to survive forsuch a long time, enduring the frequent seismic events due mainly to its structuralsystem (construction materials and techniques). Understanding the traditional wis-dom of the building’s earthquake-resistant structural system and assessing the qualityof its materials are prerequisites for a reliable evaluation of the current load-bearingstate and adequacy of the building.

The main local building material is adobe (sun-dried mud bricks), which wasalso used for constructing the load-bearing walls of this dwelling. Adobe units weremade of earth mixed with straw along with water, pressed in wooden moulds, anddried in the hot sun for a few days until they were ready to be used for the construction.The structural behavior of the adobe-bearing walls depends on:

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PLAN OF THE FIRST FLOOR

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Figure 3. Plan of the first floor (figure is provided in color online).



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1. The structural properties of the adobe bricks — quality of adobe unit, type ofjoining mortar, and ways of laying the units;

2. Their position, arrangement, connection, and interaction with the bearing andnon-bearing elements— including position and construction of openings, type,arrangement and placement of the floors and roof structure — and more impor-tantly their specific constructional detailing;

3. Their specific geometric characteristics; and4. Their relative positioning in relation to the main horizontal direction of the seismic

forces.

All of these points must be further examined.As mentioned previously, the structural efficiency of the adobe wall depends on

the specific properties and characteristics of its units. The adobe wall responds well tocompression, but its tensile strength is weak. To accurately estimate quality of theadobe construction of the specific case study dwelling, samples have been taken ofboth the adobe bricks and the plaster. In the laboratory, both the bending strength ofthe adobe brick and the tensile strength of the plaster have been measured.1

The bending strength of the adobe-brick has been measured according to ASTMC-293-02. Three-point bending tests were carried out in threemasonry units (Figure 4).As shown in Figure 4 the load was applied vertically to the fibers. The results of thebending tests are presented in Table 1. The flexural strength of the bricks was foundequal to 0.83 MPa.

For the measurement of the tensile strength of the mortars the mortar-fragmenttest method (Tassios et al. 1989) was used, using a device that allows for testing indirect tension (Katsaragakis 1987). For this purpose, I-shape specimens were made ofmortar fragments that were glued with epoxy resin between two T-shape cement-moulds (Figure 5). After testing the vertical projection of the failure area (A, Figure 5)was measured for each fragment and the tensile strength ft was obtained (Table 2). Themean value of the tensile strength of six specimens was found equal to 0.35MPa. From

Figure 4. Measurements in a simple schematic illustration for one of the three adobe units (figure is provided

in color online).

1

Laboratory tests on the properties of adobe were conducted at the Laboratory of Reinforced

Concrete, National Technical University of Athens (Athens, Greece) by Professor E. Vintzileou.



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the laboratory results, it becomes obvious that elements that respond well to tensileforces must be incorporated into the construction of the adobe walls in order toreinforce them against earthquakes and ground and wind forces.

In the examined case, the adobe walls are constructed with mortar of the samematerial as the adobe units. Thus, homogeneity is its best advantage concerning itsresponse to seismic forces. The walls are either left uncovered and give the dwelling acoarse character due to their rough texture and a morphological entity, or plaster isused to cover them. The way they form the external walls based on their modularity isshown in Figure 6. The adobe walls are 70 cm wide, 8 m average height, and are builtwith horizontally set timber ties with various dimensions (6 cm x 8 cm or 10 cm x 12cm), spaced at 70–90 cm. These timber ties are going around the building, acting asreinforcement, confirming masonry, thus the ductility and ensuring improved out-of-plane behavior of walls during earthquakes (Vintzileou and Touliatos 2008). Thecreation of these horizontal ties at regular intervals permitted the continuation ofconstruction at higher levels even though the mortar at the lower levels was not yet

Figure 5. Photograph of the T-shape cement moulds andmortar fragment (figure is provided in color online).

Table 1. Results of the bending tests

Dimensions

Specimen # L (mm) L1 (mm) b (mm) H (mm) P (Nt) ft (Mpa)

1 310 200 175 100 4200 0.72

2 380 280 165 110 4400 0.93

3 370 280 165 110 4000 0.84

— — — — — Mean value 0.83

Table 2. Tensile strength of the mortar fragment

Mortar # Nx (N) A (mm2) ft(MPa)

K1 230.69 692 0.33

K2 90.83 540 0.17

K3 403.75 860 0.47

K4 120.78 286 0.42

K5 217.60 559 0.39

K6 82.57 268 0.31

— — Average 0.35



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dried and solidified (Figure 7). Such a way of construction protects against suddensubsidence and cracking of the walls (Kouremenos 1989).

A section of the wall shows that a set of timber ties is placed along the two sidesof the walls. This parallel arrangement is never broken but only partially interruptedat the inner side of the walls whenever a closet or a fireplace is found (Figure 8).

The spacing of the horizontal timber ties along the height of the walls varies anddepends on the different phases of the construction. These phases are reflected on thepositions of the timber ties expressing the overall morphology of the building: level ofthe stone base, level of the floor and the roof, and lower and upper levels of the openings.The timber ties not only strengthen the performance of the walls against horizontalforces (e.g., seismic, wind), they are also necessary in order to assist the walls to carry theconcentrated vertical loads that are applied on them at the levels where the horizontalheavy elements of the floor and the roof rest. This assistance is very important due to thelimited compressive strength of the adobe walls. In addition, these timber ties help indistributing the loads of the beams of the floor and the roof evenly and, by doing this,protect the walls against vertical cracks (Vintzileou and Touliatos 2008).

Figure 7. Photograph of the adobe wall and timber ties (figure is provided in color online).

Figure 6. Illustration of the modularity of the adobe units (figure is provided in color online).



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The first set of timber ties is placed above the stone base in order to be protectedfrom humidity and water. Thus, stone construction forms a base of approximately0.90cm in height above the ground level on which the bearing adobe walls rest. All bearingwalls rest on stone foundations. Their width is approximately double that of the wallthat they support and they are approximately 1 m deep. The stone walls have a width of0.70 cm, with exceptional attention paid to the carving and the building of the corner-stones. The mortar assists in layering and the cohesiveness of the stones (Figure 8).

A set of timber ties is placed at the level of the floor. Timber is used to constructthe mezzanine floor of the dwelling. The floor consists of the patera—beams that bearthe wooden floor— placed right above the timber ties. The beams are made of cypressand are of circular cross-section 0.35cm in diameter and 8–10 m in length. These areplaced in holes that have already been made into the walls, 0.30–0.50 cm apart. Theboards, planks of hard wood were nailed to the beams (Figure 9).

The load bearing walls support the roof frame made of cypress wood placedabove the timber ties found in this position. This roof frame rests only on theperipheral bearing walls and not in any interior ones. The roof has been constructedas a double-pitched roof in the front part of the building (up to themiddle bearing wallof the y-direction) and as a single-pitched one at the back (beyond the middle wall).The part covered by the single-pitched roof is the later addition. The trusses of the roofin the front part are placed along the x-direction and, thus, the vertical loads arechanneled to the three bearing walls of the y-direction. At the back part, where the

Figure 8. Axonometric illustration of the historic dwelling (figure is provided in color online).



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roof is single-pitched, the loads are carried by the two walls on which the roof rests.The final layer of the roof comprises wooden boards and clay tiles that are placed onthe top boards (Figure 10).

The timber ties play a structural role even in the construction of the balconies.The fixing and construction of the balconies are interrelated to the placing of the ties.The timber ties at the level where the cantilevers of the balconies rest enable thebearing wall below to carry horizontal and vertical loads more efficiently.

Openings are part of constructions with zero structural strength — they arepoints of discontinuity and weakness (considerable wall failures occur around open-ings and usually at the four corners where various forces concentrate). Openingsinfluence directly the structural behavior of the load-bearing walls, and this is ofcourse the case for adobe walls as well. Therefore, the design and geometry of theopenings as well as their placement, juxtaposition, number, and size range are of vitalimportance (Figures 11 and 12).

The openings of the facades are organized along vertical and horizontal zoneswithin the zones of the timber ties, which define the length of windows and doors andbecome their window seals and upper parts. The reinforcement of the areas around theopenings is further improved by the two additional zones of timber ties that existwithin the levels of the top and bottom of the openings. The window case is anindependent wooden frame is additionally nailed at the transverse wooden studsthat connect the pair of timber ties at the sides of the openings (Figure 8).

The particular detailing and joining of the timber ties suggests a conscious effort—from the part of the maker — to secure their continuity: 1) along their length, 2) atthe corners, and 3) across their width (Vintzileou and Touliatos 2008).

1. Since timber parts are only 3–4 m long, joining them is necessary to produce longerpieces. For this purpose, the ends of the ties are cut diagonally and connected withnails. This way of joining which is a common one, ensures continuity but is oflimited strength (Figure 13).

2. At the corners, the sets of timber ties are connected by simply placing them the oneon top of the other. In this way the ties occur at a slightly different level at theadjacent walls (Figure 14). Since the corner- joints are of tremendous importancefor the general structural behavior of the building, additional metal joints at thelevels of the floor and the roof connect the timber ties (Figure 15). Another

Figure 9. Photograph of the patera that bear the wooden floor (figure is provided in color online).



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80×160

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purlines 60×60 every 0.50m

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purlins 60×60 every 0.50m

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Figure 10. Schematic illustration of the roof structure (figure is provided in color online).

Figure 11. Schematic illustration of the main facade of the dwelling.



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strengthening element is the placing of a diagonal piece of wood that joins thecorners at the roof level. At this level, the tying of the whole building is completed,and the cooperation of the roof structure with the load bearing walls is needed.3)Across the width of the wall the two timber ties are connected with pieces of woodthat are placed perpendicularly between them every 50 cm and are nailed to them.They are called klapes and are 54 cm long with a cross section of 6 x 8 cm. At thelevels of the floor, the roof as well as at the areas of the balconies, the klapes areomitted and are replaced by the wooden beams that rest on the walls at these levels(Figure 8).

In conclusion, we can argue that the structural strengthening of the buildingthrough the system of timber ties in an adobe wall construction is historicallyrecognized as an efficient vernacular technique of distributing seismic forces to thebearing walls since floor and roof structure do not provide satisfactory diaphragm

Figure 12. Schematic illustration of the north facade of the dwelling.

Figure 13. Photograph of the timber ties: detail along their length (figure is provided in color online).



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action to ensure proper distribution of loads according to contemporary under-standing of the term diaphragm and according to international regulations. This isthe case because the planks are nailed to the main beams, which run only in onedirection, and the walls parallel to these main beams are not connected to them(Figures 16 and 17) (Vintzileou and Touliatos 2008).

Figure 14. Photograph of the timber ties: detail at the corners (figure is provided in color online).

Figure 15. Photograph of the metal joints at the corners (figure is provided in color online).



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The structural system described herein is evaluated as providing a rationallayout of bearing elements, each having well defined roles in the proper load transferto the building foundation. Clever use of local construction materials, constructiontechniques, and craftsmanship contributed to a solid structural concept that managedto endure seismic loads, as evidenced by the building’s performance throughout itslifetime and by its limited structural damage, described in more detail later in text.

3. ASSESSMENT OF CURRENT STATUS

In any architectural project the issue of materials durability is always present. Inplanning the restoration of an adobe building, it is necessary both to determine the

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Figure 17. Schematic illustration of the structural system of the first floor.

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Figure 16. Schematic illustration of the structural system of the ground floor.



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nature of the building’s deterioration and to identify and correct the sources ofdeterioration. Such an accurate assessment of their current status is the startingpoint to propose a successful restoration that is sensitive to the integrity of the historicadobe building and to develop a maintenance program once the restoration is com-pleted (Ipekoglu 2005).

The case study dwelling has survived for more than 100 years without anymaintenance or repair, preserving its original plan, mass and facade characteristicsas well as its materials without any structural or morphological interventions. Itssurvival may be explained because of the climatic conditions of Itea, the constructiontechniques, the excellent workmanship, and exclusive use of adobe bricks as its mainconstruction material. The damages observed by a visual close-up inspection of thebearing and non-bearing elements are divided into two categories: structural damagesand non-structural damages.

1. Structural damages: Slight material deterioration is noted in some parts of the load-bearing walls of the dwelling from their interior side, and a corrosion problem innoted concerning the adobe bricks forming the outer eastern corner of the dwelling.Such collapsed sections of walls and deep cavities create structural discontinuitiesand form points of weakness in otherwise monolithic adobe walls. The roofstructure of the garden building has recently collapsed; deterioration-corrosionof the adobe bricks of the one story building in the garden is dense on all sections ofthe walls up to approximately 1 m below the roof level. In addition, the roof of themain building exhibits leaking problems, which cause staining of both external andinterior walls, affecting at the same time the quality and strength of adobe.

2. Non-structural damages: Noted damages are: deterioration of the balconies’ con-crete floors, which have replaced the original wooden ones; cracks in the plasterboth in the exterior and the interior of the building shell; cracks in the joiningbetween the load-bearing walls and the interior partitions; cracks in the interiorcorners joining the original structure with the added one; wooden shutters in badcondition; wooden frameworks of the exterior openings worn out; part of the upperfloor worn out and uneven; and missing, or severely damaged fenestration of thebuilding in the garden.

The main sources of the historic building’s deterioration are seismic activity, water,animals, material incompatibilities, and vandalism.

1. Seismic activity: Cracks observed in the inner corners of the building, added to themain one in 1890, are due to pressure from various small earthquakes that tookplace over the years and to the poor structural connection to the original building.However, there is no cracking observed on the adobe walls except some shorthairline cracks that are caused as the adobe shrinks and continues to dry. Such anobservation indicates that the historic building does not suffer from severe struc-tural damages; rather it seems to enjoy proper design and construction, sufficientfoundations, adequate materials, and a relatively good response to seismic activity.

2. Water: The cause of adobe units’ deterioration concerning the walls of the onestory building in the garden is the collapse of its roof. Thus, rainwater entersregularly and for many years inside and outside of the building, causing chemicalactivities on the building fabric. The leaking problems of the main dwelling’s roof



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are due to the weathering of the materials and their conjunctions employed in theconstruction. Load-bearing walls and related wooden elements that have beenseverely eroded by the channeling of water is one of the most frequently encoun-tered problems in adobe architecture. Successful stabilization, restoration, and theultimate survival of the historic adobe building depend upon efficiency of thestructure to shed water.

3. Animals:Micemay travel through adobewalls as they do through natural soil. Theytend to live in adobe structures, burrowing and nesting in walls or in foundations.The adobe deterioration problem reported for some parts of the load-bearing wallsof the dwelling from their interior side is due to the presence of mice, which dugholes and tunnels in order to freely circulate within the building tissue. Theseanimals undermine and destroy the structural soundness of the adobe building.

4. Material incompatibilities: The cracks caused on the surface coating of the walls aredue either to poor craftsmanship and poor quality of the plaster or inadequateconnection to the adobe walls.

5. Vandalism: The corrosion problem observed in the adobe bricks forming the outereastern corner is the result of the violent demolition of the adjacent historic dwellingwithout taking any appropriatemeasures and the long time needed to fully restore it.

It can be assessed that the major cracks that occur in both the exterior walls aswell as the partition ones are contained within the plaster, whereas satisfactorycondition is noted for the stone masonry of the base, for the adobe brick masonryof the walls above, and for the timber ties, wherever visible at the current state. We canassess that the damages that appear in the building are localized cracks in some piersand windowsills that go no deeper than the plaster. In addition, the wood of the timberties, the wooden planks, and the wooden beams of the floors are assessed to be inrelatively good condition, considering the age. The main construction material —adobe — is homogenous and in excellent condition in the parts of the building leftuntouched by the influence of environmental factors. It has survived and endured theclimatic factors (humidity, rainfall, temperature fluctuation) of the place until today,fulfilling its predicted performance (Heathcote 1995).

Summing up, we can assess that, the primary cause of material deterioration isexposure to moisture and dampness, which influence the strength of adobe bricks, andeventually allow for the degradation of the material structure. Occasional poor crafts-manship, lack of proper maintenance, and unpredicted existence of mice are additionalcauses of deterioration. It is also worth noticing that the dwelling was not damaged bythe earthquake activity, which took place recently in the area (Figures 18 and 19).

4. STRATEGY FOR INTERVENTION

The proposed strategy of intervention aims at improving the available bearingcapacity of the building particularly with respect to a possible future seismic event,taking into account the recommendations for the analysis, conservation and structuralrestoration of architectural heritage that has been recently approved by theInternational Council on Monuments and Sites (ICOMOS, Paris, France), placingemphasis on the contribution of the structural engineer to thoroughly survey andunderstand the structural behavior and material characteristics of heritage buildings



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(Lourenco 2006). Indeed, the compatibility of the restoration technology may beensured only by understanding the building as the product of a specific technologicalcivilization. Preserving and restoring a historic adobe building is most successful whenthe materials and methods used for restoration are as similar as possible to the techni-ques used in the original construction (Oxley 2003).

4.1. Preservation and Bracing Decisions

The decisions concerning the preservation and bracing of the building are basedon the following criteria:

� Conservation of the original historical materials and workmanship� Conservation of the building’s original technology� Identification and correction of the sources causing the deterioration� Development of a restoration plan that is sensitive to the integrity of the historic

adobe building� Proposed repairs that are reversible and do not cause damage to important fabric if

they have to be removed� Use of materials and construction techniques very similar to or at least compatible

with those used in the original structure� Difficulty and precariousness of combining the adobe brick elements with contem-

porary materials such as concrete or steel� Structural performance that the building has shown throughout its life-span� Difficulty of the preexisting system of construction and materials to comply with

the new building codes (Goodhew and Griffithr 2005)

Figure 18. Photograph of the main facade of the dwelling at its current state (figure is provided in color online).



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� Careful cost estimation, which will determine an economically viable budget for therestoration

� Development of a maintenance plan once the restoration is competed.

Based on these parameters the proposed intervention addresses root causes aiming at: 1)the replacement of weak bearing and non bearing elements with stronger ones; 2) theprotection of bearing and non bearing elements from humidity and erosion; and 3) thereinforcement of the structural system of the building against seismic forces withoutdisturbing its existing structural system and load transferring pattern.

4.2. Proposed Measures for Intervention

To achieve these goals, the following measures are proposed: repairing adobewalls; replacing adobe walls; replacing old surface coating; replacing and repairing of

Figure 19. Photograph of the north facade of the dwelling at its current state (figure is provided in color online).



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the clay tile roofs; replacing timber ties; repairing and replacing wooden elements(windows, doors, floors); structural reinforcement; addressing mechanical considera-tions; and maintenance (Forsyth 2008).

4.2.1. Repairing adobe walls In repairing adobe walls, every effort will be made tofind adobe bricks and mud mortar that is compatible with the fabric of the historicadobe building. Cavities will be repaired using adobe with a texture and color similarto the original raw material. They are to be filled in layers; each layer being left to drybefore being scored to provide a mechanical key before the next is applied. The holesare finally overfilled and the surface is ‘pared’ to the line of the wall. When anindividual adobe brick has partially disintegrated, it may be patched in place. Thedeteriorated material may be scraped out and replaced with appropriate adobe brick.It is necessary to spray the new adobe and surrounding area lightly with water tofacilitate a better bond. In many cases, it is recommended that fragments of theoriginal adobe brick may be grounded up, mixed with water, and reused to patchthe eroded area. In repairing cracks in adobe walls which are minimal (only 10 cm indepth or less), it is necessary to rake out the cracks to a depth a two or three times thewidth of a mortar joint to obtain a mechanical bond of the mortar to the adobe bricks.The bricks are sprayed lightly with water to increase the cohesive bond. New adobemud mortar may then be used to fill the cracks in layers. The mud mortar is to matchthe original material, color, and texture. It is important to not replace adobe mudmortar with lime or Portland cement mortar since they do not have the same thermalexpansion rate as adobe brick. With the continual thermal expansion and contractionof adobe bricks, lime or Portland cement mortars will cause the bricks — the weakermaterials— to crack, crumble, and eventually disintegrate (Cornerstones CommunityPartnerships 2006).

4.2.2. Replacing adobe walls When it is impossible to repair an adobe wall ormajor parts of it because of excessive structural damage, it is then necessary to rebuildthe wall determining how to best key in the new wall with the existing wall. Adobebricks similar to the original raw material will be used following the pattern theoriginal adobes were laid so that the joints alternate from course to course. A max-imum of three to four courses will be laid in every 2–3 days, allowing ample time forthe mud mortar joints to dry, since adding too many courses in a short period of timemay cause the adobes to shift. It is also recommended to reuse any wooden ties fromthe original construction as possible. Small-scale repairs are made by cutting out theeroded bricks and rebuilding damaged or deteriorated parts of the walls using similaradobe bricks laid with mud mortar of the same properties as the bricks. Traditionaladobe construction techniques and materials are suggested for use to repair or rebuildparts of the walls (Keefe 2005).

4.2.3. Replacing old surface coating The old surface coating suffers from naturaldeterioration and needs to be replaced. Recommendations are removal down to thesubstrate of the walls, all the way to the adobe original material. This process will bedone with care not to damage the adobe brick fabric underneath. Every effort will bemade to recoat the surfaces with the same material that originally coated the surface,which is lime plaster. Lime is one of the most sustainable, reversible, and compatible



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materials for use with adobe historic buildings because of a number of characteristicsthat define its chemical and mechanical advantages on adobe walls (McHenry 1984):

1. Stickiness— lime binds gently, adhering to surfaces even without the use of a metallath;

2. Durability — lime is very durable if successfully applied and infinitely repairable;3. Breathability — lime dries out buildings and avoids condensation problems it

allows healthy buildings with evaporative surfaces and a maintained equilibriumof moisture content in the fabric, reducing timber decay and the need for chemicaltreatment;

4. Low thermal conductivity — lime is warmer than cement plasters in cold weatherand also improves conditions in hot weather;

5. Beneficial acoustic properties; and6. Autogenous healing — lime develops may small cracks instead of individual large

cracks that occur in cement plastered buildings.

When water penetrates these fine cracks, it dissolves ‘‘free’’ lime and brings it to thesurface. As water evaporates, the lime is deposited and begins to heal the cracks itself),protection (lime is a fire retardant, protecting timber) (US Department of the Interior2004). All bearing walls will be covered with new lime plaster, as indicated by currentpractices in order to stabilize the structure. In preparation for application of the limeplaster, limewater will be used in wetting the substrate, which increases the adhesiveand cohesive characteristics of the adobe. A chemical bond is formed between the limeand the mud, as the limewater dries and re-carbonates in the adobe walls. The mostcommon local weatherproofing and durable treatment is a permeable lime plaster ofthree parts washed concrete sand to one part lime putty applied in three coats. Such alime based plaster is designed to prevent erosion and abrasion of the adobe substratewhile allowing the free passage of water and a degree of thermal and moistureexpansion to take place. This is supported on an expanded mesh of galvanized wirefixed to the wall with galvanized nails of sufficient length to securely attach it. Themetal mesh serves the plaster to adhere to adobe substrates and protects the wall fabricagainst cracking. This way the structural performance of the bearing wall system willbe improved in both vertical and horizontal direction. In addition the structure will bebetter protected against humidity and other environmental conditions. Also, verticaland horizontal corners where plaster meets wood surfaces (i.e.. window and doorframes) will also be waterproofed and reinforced with metal mesh to prevent crackingand spalling. The first coat serves to fill low spots and small voids and to provide a flat,uniform surface for application of the final coats. Plaster will be applied with force.The second coat will be applied with adequate force to prevent cracking and thenleveled with a straightedge to a thickness that covers irregularities in the leveling coat.The finish coat of lime plaster may be slightly richer (use more lime) than the levelingor second coat. Finally, color coat will be applied on the stucco surface instead ofpaints of oil or synthetic plastic base, which tend to form a moisture barrier causingcracks and peeling.

4.2.4. Replacing and repairing of the clay tile roofs Awatertight roof is essentialin the preservation of a historic structure. The roof of the garden building will



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be completely replaced; any historic material that might be incorporated into the newroof will be carefully selected, stored, and reused. The new roof will be constructedwith its original form and detailing using similar materials, and will not be heavierthan the roof it is replacing. The old clay tile roof of the main building is intended forrestoration and maintenance with its original form and materials. A thorough exam-ination of the roof is recommended to start with an appraisal of the existing conditionand quality of the roofing material itself. Before any repair work is performed, acomplete internal and external inspection of the roof will be planned to determine allthe causes of leaking and to identify the alternatives for repair. It appears that the roofstructure is sound and that the leaking problem is limited to deteriorated gutters,flashing, and downspouts. Roof drains will be replaced in kind to match the historicmaterial to secure protection against rainfall erosion. Copper is preferred for use inhistoric clay tile roofs because of its durability and long-lasting qualities.The historical wooden trusses of the main dwelling will be conserved. All timberthat may be affected by leaks in the roof will be examined carefully and repairedif needed.

Reinforcement of their knots is also recommended. This way, all vertical roofloads will be fully transferred to the bearing walls and the structure will be insulatedagainst humidity and other environmental factors. The roof structure is to be con-cealed. Therefore, it may provide a cavity space within, in which insulation materialsmay be efficiently used. In addition, the old clay tiles will be retained and reused. Theyare not only one of the most distinctive historic roofing material because of theirshape, color, profile, pattern, and texture, but they are also harder and better suited toweather the erosive action of rainwater. The tiles appear to be intact but no longersecurely attached to the roof substrate due to deterioration of the fastening system orroofing members. The old tile roof is to be stripped of all its tiles very carefully sinceold clay tiles are inherently fragile, in order to re-lay the tiles with new fastenings. Allroof tiles will be numbered and a diagram will be drawn showing the location of eachtile to ensure that it is reinstalled in its original location. The tiles will be reattachedone-by-one, after the necessary repairs have been made to the roof. The use oftraditional lime mortar is recommended because it is more watertight and compatiblewith the old clay tiles (US Department of the Interior 2004).

4.2.5. Replacing timber ties The vulnerability of timber ties to decay depends onthe quality and species of timber. It is essential to identify the type of decay mechan-isms and provide specific solutions to prevent their continued activity at present.Timber ties will be replaced with similar timber ties wherever needed without disturb-ing their original system. In some cases, instead of replacement, reinforcement andrepairing of the existing ones may be recommended. The particular detailing of theirjoints can also be examined and either redesigned or simply reinforced.

4.2.6. Repairing and replacing wooden elements (windows, doors, floors)

Historic wooden windows, doors, floors, staircases, and other original details arean important aspect of the architectural character of the building. Their design,craftsmanship, and other qualities make them worthy of preservation. Evaluatingtheir significance and planning for their repair is a complex process. The primaryemphasis is on the issues of their significance and repair including evaluation oftheir physical condition, techniques of repair, and design considerations when



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replacement is necessary. More specifically, the key to successful planning forfenestration restoration is a careful evaluation of existing physical conditions ona unit-by-unit basis. In any evaluation, it is essential to note the fenestrationlocation, the condition of the paint, and the condition of the frame, sill, andsash. Many factors such as poor design, moisture, vandalism, insert attack, andlack of maintenance can contribute to wood deterioration, but moisture is theprimary contributing factor in wooden fenestration decay. All fenestration unitswill be inspected to see if water is entering around the edges of the frame and, if so,the joints or seams will be caulked to eliminate this danger. One clue to the location ofareas of excessive moisture is the condition of the paint; therefore, each fenestration willbe examined for areas of paint failure. The key to longevity lies in the importance ofgood detailing, keeping the timbers free of dampness, and implementing regular andappropriatemaintenance. Following the inspection and analysis of the results, the scopeof the necessary repairs will be evident and a plan for the restorationmay be formulated.Generally the actions necessary to return fenestration to ‘like new’ condition falls intothree broad categories: routine maintenance procedures, structural stabilization, andwood restoration and conservation techniques.

Routine maintenance repairs are usually labor intensive and relatively uncom-plicated. It normally includes the following steps: some degree of interior and exteriorpaint removal, sash removal and repair (including re-glazing where necessary), repairsto the frame, weather-stripping and reinstallation of the sash, and repainting.Following such relatively simple repairs, the fenestration becomes weather tight,‘like new’ in appearance, and serviceable for many years to come. Both the historicmaterial and the detailing and craftsmanship of the original fenestration are preserved(US Department of the Interior 2004).

Some fenestration show some additional degree of physical deterioration, espe-cially in the vulnerable areas mentioned previously, but even badly damaged fenestra-tion may be repaired using simple processes. Partially decayed wood can bewaterproofed, patched, built-up, or consolidated and then painted to achieve asound condition, good appearance, and greatly extended life. One established techni-que for repairing wood that shows signs of rot is to dry the wood; treat decayed areaswith a fungicide; waterproof with two or three applications of boiled linseed oil; fillcracks and holes with putty; and — after a ‘‘skin’’ forms on the putty — paint thesurface. Wood may also be strengthened and stabilized by consolidation, usingepoxies that saturate the porous decayed wood and then harden. When parts of theframe or sash are so badly deteriorated that they cannot be stabilized there aremethods that permit the retention of some of the original fabric. These methodsinvolve replacing the deteriorated parts with new matching pieces, or splicing newwood into existing members. The techniques require more skill and are more expen-sive than any of the previously discussed alternatives. It may be necessary to removethe sash and/or the affected parts of the frame and have a carpenter reproduce thedamaged or missing parts (US Department of the Interior 2004).

In addition, all wooden elements embedded in the historic building will beexamined carefully for moisture contents that favor decay and insect attacks. Thevarious wood restoration and conservation techniques needed may be grouped aspartial or complete replacement, mechanical reinforcement, consolidation by impregna-tion, and reinforcement and consolidation. It is important to keep in mind that an oldwood contains valuable information about the building of which it is a part; therefore



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repair is advisable before replacement. There are various techniques of wood restora-tion recommended (US Department of the Interior 2004):

1. Timber-to-timber repairs. In traditional carpentry, timber-to-timber repair is themost obvious choice when selecting a technique. Where old wood is being partlyreplaced, the new wood is carefully inserted into the old wood where the unsoundold wood has been neatly chiseled away and usually undercut.

2. Metal reinforcement. Such a repair choice has been used for centuries in timberconstruction. Steel scrap and threaded bars can be the most cost-effective andconservative repair (reversible apart from a few screw or bolt holes).

3. Resin repairs. Resin repair allows a piece to be retained that otherwise would bediscarded forever. Glues and resins are specialist materials that are to be used in thecorrect conditions and strictly to manufacturer’s instructions.

Although the retention of original fenestration is the guiding principle for therestoration project, there is a point when the condition of a specific fenestration mayclearly indicate replacement. If some parts are still sound enough there may beretained and patches inserted. When deteriorated wooden elements of the historicbuilding need replacement, it is best to use materials compatible with the historicmaterial; the new material will match the details and craftsmanship of the original aswell as the color, surface texture, surface reflectivity, and finish of the originalmaterial. The decision process for selecting replacement fenestration will not beginwith a survey of the contemporary products that are available as replacements, butwith a look at the original fenestration which are being replaced. It will attempt tounderstand and record the contribution of the fenestration to the appearance of thefacade, the pattern of the openings and their size, the frame and sash proportions, theconfiguration of frames and profiles, the type of wood, the paint color, the glasscharacteristics, and all associated details such as other decorative elements (USDepartment of the Interior 2004).

4.2.7. Structural reinforcement The historic building is intended to be structurallyreinforced to survive earthquakes without damaging its integrity and significance.Planning the retrofit of the case study dwelling is a process that requires teamwork onthe part of engineers and architects. A number of seismic strengthening schemes willbe examined, developed, and studied to determine their compatibility with existingconstruction; reliability; redundancy; impact on architectural, mechanical, and elec-trical systems; suitability for phasing of construction work; costs; and detailed imple-mentation requirements.

Recognition of the configuration of the historic structure and inherent areas ofweakness’ are essential to addressing appropriate alternatives for seismic retrofit. Theplan and elevation are as important as building materials as structural systems indetermining the historic building’s survival in an earthquake. The restoration plan willinclude a system of reinforcement that will be introduced sensitively and is reversibleto the greatest extent possible to allow removal for future use of improved systems andtraditional repair of remaining historic materials; its design, placement, patterning,and detailing respects the historic character and integrity of the building whetherhidden or exposed.



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The historic building will be seismic upgraded using a flexible approach to thebuilding codes for moderate earthquakes. To ensure the survival of the structure andsatisfaction of some minimum requirements in an earthquake, inherent seismic defi-ciencies of the building— such as poor floor to wall framing connections, non-bracedadobe walls and lack of an effective roof diaphragm — are recommended to becorrected (US Department of the Interior 2004). The formation of a stiff peripheralzone (i.e., a timber diaphragm compatible to the original materials that will provide alevel base for the roof) will improve the performance of the bearing walls under seismicforces. In addition, a floor diaphragm will be provided by replacing the worn-outwooden floor planks with sufficiently thick, strong plywood, which will be nailed onthe main beams and connected to the vertical elements of the building (the adobewalls). This way, the philosophy of the transfer of vertical loads of the intermediatefloors to the bearing walls will be maintained, assuring improved stiffness to avoidundesired deflections. At the same time a stronger diaphragm action will also beachieved at the same location as in the original building, which contributes to thebetter performance of the bearing walls during earthquakes.

4.2.8. Addressing mechanical considerations Water, waste, and vent pipingalong with electrical systems will be installed to accommodate current needs of thenew owners. Moreover, an appropriate heating system (i.e., a radiant panel-typesystem) will be chosen which will take advantage of, or at least recognize, the thermalmass and lag effect of adobe walls. The selected mechanical system will require theleast intrusion into the historic fabric of the building and could be updated or alteredwithout major intervention into the wall and floor systems. The primary focus will beto describe ways to achieve the maximum energy savings in the historic buildingwithout jeopardizing its architectural, cultural and historical qualities (Weaver 1997).

4.2.9. Maintenance As soon as restoration will be completed, a plan of continuingmaintenance will be initiated. Cracking in adobe walls and all water leaks will be notedand remedied at their earliest possible stages. The roof will be inspected periodicallyfor broken tiles and for leaks in the interior of the building. Surface coatings will alsobe inspected frequently and repaired or replaced as needed. Observing adobe buildingsfor subtle changes and performing maintenance on a regular basis is recommended inorder to stabilize a historic adobe building (Weaver 1997).

5. CONCLUSIONS

The historic dwelling discussed above is a significant part of local culturalheritage and deserves to be preserved for future generations. Today, it is unoccupied,neglected, and exposed to environmental elements. It offers an opportunity for anapplication of the restoration techniques and the methodology of intervention dis-cussed herein. This article records and interprets all the data of the building from thearchitectural, technological, and structural points of view. The restoration proposalfollows the assessment and analysis of the historic evolution of the building as well asthe diagnosis of the damages the dwelling has undergone. On the completion of thearchitectural–structural analysis, it is evident that the notion of typology and archi-tectural character is considered and examined as a value that — with the aestheti-c–historical values and the construction quality–authenticity, which heavily depends



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on adobe bricks and timber ties, — constitute the main criteria regarding its preserva-tion and restoration. In conclusion, to attempt a competent preservation and main-tenance of an adobe building is a unique challenge that requires to develop an in-depthknowledge of adobe as a construction material, understanding the adobe historicbuilding as a system, and understanding the forces of nature that seek to return thebuilding at its original state. Such restoration may serve to sustain the embeddedknowledge about traditional construction materials and techniques and even supportit scientifically.

ACKNOWLEDGEMENT

The authors would like to thank Professor Elli Vintzileou for her patient advice,criticism and discussion throughout the writing process. We are also very grateful forthe laboratory tests she carried out at the Laboratory of Reinforced Concrete,National Technical University of Athens (Athens, Greece).

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Documents

Adobe and Timber