1 INTRODUCTION

All natural stone monuments are affected by weathe-ring. At many historical monuments weatheringdamages are alarming. Scientific characterisation,evaluation, quantification and rating of stonedamages are essential for effective and economicmonument preservation measures. Determination ofdamage indices means an innovative step of damageevaluation derived from improvement of monumentmapping. The monument mapping method isapproved as well-experienced procedure contribu-ting to reliable damage diagnosis at stone monu-ments. This internationally accepted non-destructivemethod guarantees precise classification, registra-tion, documentation and evaluation of stone typesand degradation phenomena at natural stonemonuments (Fitzner, Heinrichs & Kownatzki 1995,Fitzner, Heinrichs & Kownatzki 1997, Fitzner,Heinrichs & Volker 1997a, Fitzner & Heinrichs1998a, Fitzner & Kownatzki 1997, Kownatzki 1997,

Kownatzki & Fitzner 1999). The method can beapplied to all stone types and to all stonemonuments. It provides detailed information for theentire stone surface of monuments. Specialcomputer-programmes have been developed forprocessing, illustration and quantitative evaluationof mapping information.

Evaluation, quantification and rating of stonedamages by means of monument mapping is basedon objective description and registration ofweathering forms according to type and intensity.By means of maps, all weathering forms get exactlylocated. Type, intensity and distribution of theweathering forms are evaluated as indicators forweathering processes and environmental impacts.Evaluation of weathering forms contributes to theassessment of weathering progression and to thecalculation of weathering rates considering environ-mental situation, stone types as well as monumentcharacteristics such as location, exposition, geo-metry and utilisation.

FITZNER, B., HEINRICHS, K. & LA BOUCHARDIERE, D. (2002): Damage index for stone monuments.- in: Galan, E. & Zezza,F. (ed.): Protection and Conservation of the Cultural Heritage of the Mediterranean Cities, Proceedings of the 5th InternationalSymposium on the Conservation of Monuments in the Mediterranean Basin, Sevilla, Spain, 5-8 April 2000: 315-326, Swets &Zeitlinger, Lisse, The Netherlands.

Damage index for stone monuments

B. Fitzner, K. Heinrichs, D. La BouchardiereGeological Institute – Aachen University of Technology, Aachen, Germany

ABSTRACT: Precise diagnosis is required for characterisation, interpretation, rating and prediction of theweathering damages at stone monuments and is vital for remedy of stone damages and sustainable monumentpreservation. Quantitative rating of damages represents an important scientific contribution to reliable damagediagnosis at stone monuments. Damage indices are introduced as new tool for scientific quantification andrating of stone damages. Application of damage indices improves stone damage diagnosis and is very suitablefor evaluation and certification of preservation measures and for long-term survey and maintenance of stonemonuments. Importance and use of damage indices are presented for monuments in Germany, Malta, Jordan,Egypt and Brazil.

RESUMEN: La caracterización, interpretación, valoración y predicción de los daños de alteración enmonumentos de piedra requieren un diagnóstico preciso de los mismos. Este tipo de diagnóstico esfundamental para remediar los daños en la piedra y para una conservación adecuada de los monumentos. Lavaloración cuantitativa de los daños representa una contribución científica importante para un diagnóstico dealteración adecuado en monumentos pétreos. Los índices de daños se introducen como una nueva herramientapara la cuantificación y valoración científica de los daños en piedra. El uso de los índices de daños supone unpaso hacia adelante en el diagnóstico de alteración de la piedra y es muy adecuado para la evaluación ycontrol de las medidas de conservación, así como para estudios a largo plazo y el mantenimiento demonumentos hechos en piedra. La importancia y el uso de índices de daños se presentan para diferentesmonumentos en Alemania, Malta, Jordania, Egipto y Brasil.

Damage categories have been established alreadyas practical tool for subsequent rating of allindividual damages. Based on defined schemes, allweathering forms – considering different intensities– are related to damage categories. Determination,illustration and quantitative evaluation of damagecategories contribute to risk estimation and to riskmanagement.

Damage indices are introduced now forconclusive quantification and rating of stonedamages. Determination of damage indices is basedon quantitative evaluation of damage categories.Damage indices complete a consistent and con-vincing approach to characterisation, evaluation,quantification and rating of stone damages. Theapplication of the modular components “weatheringforms”, “damage categories” and “damage indices”allows detailed damage diagnosis of entire stonemonuments or single structures (Fig. 1). Theindividual steps of monument mapping procedure,data processing and evaluation are presented inFigure 2.

WEATHERINGFORMS

Detailed description ofindividual weathering

phenomena withquantification of intensities.

↓Definition of damage categories,

relating of weathering formsto damage categories

↓

DAMAGECATEGORIES

Rating of individualweathering damages.

↓Definition of damage indices,calculation of damage indices

from proportion of damage categories↓

DAMAGEINDICES

Conclusive quantificationand rating of damages.

Figure 1. Damage diagnosis.

Maps

- lithotypes- weathering forms

Weathering formsrelated to

damage categories

Informationfile II

- lithotypes- weathering forms- weathering rates- sequences of weathering forms

Quantitativeevaluation

Quantitativeevaluation

Maps

- damage categories

Calculation ofdamageindices - damage

categories

MONUMENTMAPPING

- lithological mapping- mapping of weathering forms

Monumentplan

Classification oflithotypes

Classification ofweathering forms

Digitalmonument plan - lithotypes

- weathering forms- planimetric data

Informationfile I

Symbols fordata processing

Figure 2. Monument mapping. Data processing and evaluation.

2 DETERMINATION AND APPLICATION OFDAMAGE INDICES

Damage indices for monuments are determinedconsequently via weathering forms and damagecategories. Weathering forms represent the visibleresult of weathering processes which are initiatedand controlled by interacting weathering factors.Weathering forms are used for detailed descriptionof individual weathering phenomena (Fig. 1). Bymeans of monument mapping all weathering formsat stone monuments are registered in detailaccording to type, intensity and distribution. Theobjective and reproducible registration and docu-mentation require a standardised classificationscheme of weathering forms. Such a classificationscheme has been established, based on investigationat monuments world-wide considering differentstone types, monuments and environments (Fitzner,Heinrichs & Kownatzki 1995).

Parameters for classification of intensities ofweathering forms have been proposed. A standardintensity classification for all weathering forms isnot feasible. It should be adjusted to the monumentsconsidering the whole range of intensities. Theexample presented in Table 1 reveals the necessityof individual intensity classification. It refers tostudies at historical limestone monuments inCairo/Egypt. Here, the different intensity range ofweathering forms corresponds to different size ofdimension stones used for the two monuments.

Table 1. Intensity classification of the weathering form “back weathering” for two monuments in Cairo / Egypt.

Intensity classification for the weathering form “back weathering (W)“according to depth of back weathering in cm

Monument

Intensity 1 Intensity 2 Intensity 3 Intensity 4 Intensity 5 Intensity 6 Intensity 7

El-Merdani Mosque –composed of smalldimension stones

< 0.2 0.2 – 0.5 0.5 – 1 1 – 3 3 – 5 5 – 10 > 10

Great Pyramid of Cheops– composed of hugedimension stones

< 5 5 – 15 15 – 25 25 – 50 50 – 75 75 – 100 > 100

Weathering forms serve for precise description ofstone degradation phenomena. Damage categorieshave been established for comparative rating ofindividual damages. Six damage categories havebeen defined (Tab. 2). Based on defined schemes, allweathering forms with their different intensities arerelated to damage categories. The transition schemes“weathering forms – damage categories“ must con-sider the historical value and the function ofdimension stones and the proportion “degradatedstone parts / total dimension stone”. The schemesshould be discussed with experts involved inmonument preservation activities like monumentowners, architects, engineers and restorers.Examples of schemes relating weathering forms todamage categories are presented in Fitzner,Heinrichs & Kownatzki (1995), Kownatzki &Fitzner (1999), Heinrichs & Fitzner (1999).

Tables 3 and 4 present two examples of transitionschemes “weathering forms – damage categories”.For the Church of São Francisco de Assis in OuroPreto/Brazil, Table 3 shows the proposed damagecategories for the weathering form ”relief“considering its different intensities. Same range ofintensities has been stated for ashlar and architec-tonic decoration. For architectonic deco-ration anddimension stones of high historical and artisticalvalue the intensity classes of ”relief“ have beenattributed to higher damage categories than forashlar. Table 4 shows the proposed damage cate-gories for the weathering form “relief“ for a Minsterin Germany and the Great Pyramid of Cheops inEgypt. A very different intensity range of thisweathering form can be stated. The proportion“degradated stone parts / total dimension stone” hasbeen considered in this case.

Table 2. Definition of damage categories.

Damage category 0 – no visible damages Damage category 3 – moderate damages

Damage category 1 – very slight damages Damage category 4 – severe damages

Damage category 2 – slight damages Damage category 5 – very severe damages

Table 3. Weathering form “relief” related to damage categories. Consideration of different structures of a monument. Church of SãoFrancisco de Assis in Ouro Preto / Brazil.

Weathering form: Relief (R) – Morphological change of the stone surface due to partial orselective loss of stone material.

Intensities - depth of relief in mm

Church of São Francisco deAssis – Ouro Preto / Brazil

< 2 2 – 5 5 – 10 10 – 30 30 – 50 50 – 100

Ashlar 1 2 3 4 4 5

DA

MA

GE

CA

TE

GO

RIE

S

Architectonic decorationand other dimensionstones of high value

2 3 4 5 5 5

Table 4. Weathering form “relief” related to damage categories for different monuments.

Weathering form: Relief (R)

Minster St. Quirin –Neuss / Germany,composed mainly of very smalldimension stones

< 0.5 0.5 - 1 1 – 2 2 – 3 > 3

Great Pyramid of Cheops –Cairo / Egypt,composed of huge dimensionstones

Intensities -depth of reliefin cm

< 5 5 – 15 15 – 25 25 – 50 > 50

DAMAGE CATEGORIES 1 2 3 4 5

Damage indices are calculated from damagecategories (area-%). Linear and progressive damageindex have been defined (Tab. 5). The damageindices range from 0 to 5.0. According to the definedcalculation modes, the linear damage indexcorresponds to average damage category, whereasthe progressive damage index emphasises proportionof higher damage categories (Tab. 6). Differencesbetween linear and progressive damage indexincreases as proportion of higher damage categoriesincreases.

Following relation arises:

progressive damage index ≥ linear damage index.

The application of damage indices allows a reliableand reproducible quantification and rating of stonedamages and contributes to monument preservation.It provides important information on need andurgency of interventions. In Figure 3 the aims andthe different application modes of damage indicesare presented.

Table 5. Calculation of damage indices.

LINEAR DAMAGE INDEXDIlin=

100)5()4()3()2()1()0( ⋅+⋅+⋅+⋅+⋅+⋅ FEDCBA

↓↓

100)5()4()3()2( ⋅+⋅+⋅+⋅+ FEDCB

PROGRESSIVE DAMAGE INDEXDIprog=

100)5()4()3()2()1()0( 222222 ⋅+⋅+⋅+⋅+⋅+⋅ FEDCBA

↓↓

100)25()16()9()4( ⋅+⋅+⋅+⋅+ FEDCB

A = Area (%) – damage category 0B = Area (%) – damage category 1C = Area (%) – damage category 2

D = Area (%) – damage category 3E = Area (%) – damage category 4F = Area (%) – damage category 5

∑ =F

A100

Table 6. Examples of linear and progressive damage indices.

Proportion of damage categories - area-%

Damagecategory 0

Damagecategory 1

Damagecategory 2

Damagecategory 3

Damagecategory 4

Damagecategory 5

Lineardamage indexDIlin

Progressivedamage indexDIprog

0 0 0 100 0 0 3.00 3.00

0 0 30 40 30 0 3.00 3.10

0 20 20 20 20 20 3.00 3.32

40 0 0 0 0 60 3.00 3.87

AIMS APPLICATION AIMS (No.)

1

GENERAL AIMConclusive quantification and rating

of stone damages for entiremonuments or single structures

Determination of damage indicesfor an entire monument 1, 5, 6

2Comparison and ranking

of different monuments with respectto state of damage

Determination of damage indicesfor single structures

1, 3,5, 6

3

Comparison and ranking of differentstructures of a monument with respect

to state of damage considering e.g.different age, orientation or other

exposition characteristics, zonationsof damages etc.

Determination of damage indicesfor different monuments,assemblies of monuments

1, 2, 5, 6

4Comparison and rating of stone

materials concerning theirsusceptibility to degradation

5 Risk estimation

Determination of damage indicesfor individual stone types

1, 3, 4,5, 6

6Contribution to risk management,judgement of need and urgency

of intervention

7 Certification / long-term controlof preservation measures

Determination of damage indicesbefore and after preservation

measures1, 5, 6, 7, 9

8Long-term survey of monuments with

identification / quantification ofdamage progression

9 Contribution to maintenanceof stone monuments

Determination of damage indicesin the frame of regularreevaluation activities

1, 3, 4, 5, 6,7, 8, 9

Figure 3. Damage indices. Aims and application modes.

3 EXAMPLES

Application and importance of damage indices arepresented at five examples:

1) Monuments carved from bedrocks in Petra /Jordan – damage indices for entire monuments,ranking of monuments,

2) Church of Sta. Marija Ta´ Cwerra in Siggiewi /Malta - damage indices for an entire monumentand single structures, characterisation of damagezonation,

3) El-Merdani Mosque in Cairo / Egypt – damageindices for characterisation of damage zonation,

4) Church of São Francisco de Assis in Ouro Preto /Brazil – damage indices for a single structure,rating of stone susceptibility to degradation,

5) Minster St. Quirin in Neuss / Germany – damageindices for certification of restoration measuresand long-term survey / maintenance of a monu-ment.

3.1. Monuments carved from bedrocksin Petra / Jordan

The monuments of ancient Nabataean Petra in southwest Jordan rank among the most importanthistorical monuments in the world. In 1985 Petra hasbeen inscribed into the UNESCO-list of worldcultural heritage. Almost one thousand monumentslike tombs and sanctuaries were carved frombedrocks about 2000 years ago. Most of thesemonuments appear as facade with chambers behind(Fig. 4). At all monuments damages can be stated. In1998 the World Monument Fund has inscribed Petraon the list of the one hundred most endangeredmonument assemblies of the world.

Within the frame of the research project”Systematic registration and evaluation of damagesat monuments in Petra“ – funded by DeutscheForschungsgemeinschaft (DFG) – studies have beenexecuted at Petra monuments. Damage diagnosis hasbeen focussed on material properties and onweathering state of the twenty-five distinguishedlithotypes.

Figure 4. Tomb No. 676 – Petra / Jordan.

Figure 5. Map of damage categories with quantitativeevaluation. Tomb No. 676 – Petra / Jordan.

Environmental influences as well as the differentmonument characteristics like location, geometryand exposition have been considered (Fitzner &Heinrichs 1998b, Fitzner & Heinrichs 1999,Heinrichs & Fitzner 1999, 2000). One aim of thesestudies is the quantification of the state of damageand a ranking of monuments regarding urgency ofpreservation measures. For this purpose damageindices have been established and used for the firsttime. Weathering forms at the monuments have beenregistered by monument mapping. This informationhas been related to damage categories according to ascheme adjusted to the Petra monuments (Fig. 5).

Damage indices have been determined forconclusive quantification and rating of damages(Fig. 6). The results line out the wide range ofdamages at the monuments. The ranking of themonuments corresponds to increasing need andurgency of preservation measures.

0 1 2 3 4 5

455

813

229

649

12

675

771

90

137

70 (N)

450

676

452

634

239

778

770

9 (W)

9 (N)

763

731

70 (E)

9 (E)

9 (S)M

onum

ents

(N

umbe

ring

acco

rdin

g to

BR

ÜN

NO

W &

VO

N D

OM

AS

ZE

WS

KI 1

904)

Damage index

Progressive damage indexLinear damage index

Figure 6. Ranking of monuments by damage indices, Petra /Jordan.

3.2. Church of Sta. Marija Ta´ Cwerrain Siggiewi / Malta

Studies at the Church of Sta. Marija Ta´ Cwerra inSiggiewi in the Southwest of Malta have beencarried out in the framework of the E.C.-Researchproject "Marine spray and polluted atmosphere asfactors of damage to monuments in the Medi-terranean coastal environment“ (Fitzner, Heinrichs& Volker 1997b). The church was built in the 16thcentury and rebuilt in the 18th century (Fig. 7).Tertiary Globigerina limestone was used forconstruction. This soft stone material has been usedfor Maltese monuments from antiquity until today.The lowermost parts of the church are covered withplaster.

According to interdisciplinary studies, saltweathering due to marine environment is theessential weathering process causing degradation ofthe very porous limestone. High deposition of saltfrom the atmosphere has been stated for themonument. The lower parts of the monuments arealso affected by highly salt-loaded rising humidityresulting in salt accumulation and intensification ofsalt weathering processes. Halite is the predominantsalt mineral. Seasonal and diurnal variations ofrelative humidity create high frequencies of saltmobilisation and salt crystallisation - cycles.

Damage indices have been determined viaweathering forms and damage categories for theentire monument and for the four facades of the free-standing monument. Vertical zonation of damages atthe facades has been characterised by means ofdamage indices (Figs 8, 9). For the entire monu-ment high damage indices have been stated. Thelinear damage index DIlin = 2.73 and the progressivedamage index DIprog = 3.07 indicate the need ofintervention. Considering the age of the monument,the damage indices show a high susceptibility of theGlobigerina limestone to salt weathering.

Comparing the damage indices of the fourfacades, the south facade shows the most severestate of damage (DIlin = 3.38, DIprog = 3.64). This isdue to extreme microclimatic variations at thisfacade causing intense salt weathering processes. Atall four facades two zones of damages can bedistinguished: an upper zone with mainly slightdamages and a lower zone with mainly severe oreven very severe damages (Fig. 8). The lower zonecorresponds to parts of the church affected by salt-loaded rising damp. Salt load in these lower part isremarkably higher than in the upper part. Thedamage indices for these two zones – presented asexample for the south facade (Fig. 9) - reflect thedifferent state of damage as consequence of differentsalt load (south facade - lower part: DIlin = 4.64,DIprog = 4.69; upper part: DIlin = 2.40, DIprog = 2.54).Prospective interventions have to be addressed to thelower parts of the church.

Figure 7. Church of Sta. Marija Ta´ Cwerra. Siggiewi / Malta.

Figure 8. Map of damage categories. Church of Sta. Marija Ta´Cwerra. South facade.

0

1

2

3

4

5

Ent

irem

onum

ent

Eas

t fac

ade

Sou

th fa

cade

Wes

t fac

ade

Nor

th fa

cade

Sou

th fa

cade

,lo

wer

par

t

Sou

th fa

cade

,up

per

part

Dam

age

indi

ces

Linear damage index

Progressive damage index

Figure 9. Damage indices. Church of Sta. Marija Ta´ Cwerra.

3.3. El-Merdani Mosque in Cairo / Egypt

El-Merdani Mosque is located in the historic centerof Cairo. The Islamic Cairo has been declared byUNESCO as “World cultural heritage”. The mosquewas built in the 14th century as one of the finestexamples of Islamic architecture in Cairo. Porouslimestones from the Mokattam mountains east ofCairo were used for construction. The mosque wasrestored a century ago, but it needs again inter-vention. Especially damages in the lower parts of themonument are striking (Figs 10, 11).

Within the framework of the EC-ConcertedAction ”Study, characterisation and analysis of de-gradation phenomena of ancient, traditional andimproved building materials of geologic origin usedin construction of historical monuments in theMediterranean area“ studies have been carried out atpilot areas of the mosque. The results have revealedan extreme example of salt weathering damages,mainly induced by salt-loaded rising humidity. Thissituation can be observed at many historical monu-ments in Cairo. Defect water and sewage systemscauses rising of the ground water table and pollutionof the ground water.

The study of El-Merdani Mosque demonstratesthe use of damage indices for quantitative evaluationof damage zonation. In order to quantify damages invertical profile, damage indices have been calculatedfor each row of dimension stones (Figs 10, 12). Theprofile illustrates increase of damage indices fromthe lowermost part of the investigation area tomaximum in the middle to upper part, followed bydecrease of damage indices towards the uppermostpart of the investigation area.

The part with highest damage indices representsthe main zone of salt precipitation resulting in mostintense salt weathering processes and stone degra-dation. Presented damage indices contribute to riskestimation and to identification of risk areas at El-Merdani Mosque.

Figure 10. El-Merdani Mosque – Cairo/Egypt. Lower part ofthe SE-facade with numbering of rows of dimension stones.

Figure 11. Map of damage categories. El-Merdani Mosque.Lower part of the SE-facade.

0 1 2 3 4 5

Row 1

Row 2

Row 3

Row 4

Row 5

Row 6

Row 7

Row 8

Row 9

Row 10

Row 11

Row

s of

dim

ensi

on s

tone

sfr

om b

otto

m (

1) to

top

(11)

Damage indices

Progressivedamage index

Linear damageindex

Figure 12. Damage indices - vertical profile. El-MerdaniMosque. Lower part of the SE-facade.

3.4 Church of São Francisco de Assisin Ouro Preto / Brazil

Ouro Preto can be considered as masterpiece ofcolonial architecture in Brazil. UNESCO hasdeclared this town as ”World cultural heritage“. Thechurch of São Francisco de Assis was built anddecorated in the second half of the 18th century bythe famous Brazilian artist Antonio FranciscoLisboa, known as Aleijadinho. Local quartzites wereused for the ashlar parts of the church, soapstonesfor the decoration parts of the facades.

Studies have been carried out at the church in theframework of the German-Brazilian project ”IDEAS– Investigation into devices against environmentalattack on stones“. Use and significance of damageindices are presented for the soapstone decoration ofthe main portal (Fig. 13). Soapstone represents a softstone material that can be worked easily. Two differ-ent soapstone varieties were used for construction ofthe decoration part of the main portal. Fewdegradated stone pieces were replaced in the frameof previous restoration. Damage indices have beendetermined for the entire decoration part in order toestimate need of intervention. Additionally, damageindices have been calculated individually for thedifferent soapstone types in order to rate and com-pare their susceptibility to weathering. This informa-tion contributes to selection of appropriate soapstonevarieties in case of stone replacement measures.

Figure 13. Church of São Francisco de Assis, Ouro Preto /Brazil. Soapstone decoration of the main portal.

Figure 14. Map of damage categories. Church of São Franciscode Assis, Ouro Preto / Brazil. Soapstone decoration of the mainportal.

Table 7. Damage indices. Church of São Francisco de Assis.Soapstone decoration of the main portal.

Damage index

linearDIlin

progressiveDIprog

Entire soapstone decoration 2.42 2.78

Soapstone – type 1 1.99 2.25

Soapstone – type 2 3.49 3.82

Soapstone – type 3 1.40 1.74

Figure 14 shows the map of damage categoriesfor the soapstone decoration part. Damage indicesare presented in Table 7. The damage indices for theentire soapstone decoration indicate the need ofintervention (DIlin = 2.42, DIprog = 2.78). Severe andvery severe damages predominantly occur at soap-stone – type 2, very slight and slight damagesmainly at soapstone – type 1. Comparing the damageindices for the two soapstone types, the highersusceptibility of soapstone – type 2 to degradation isobvious. Intervention at those parts made fromsoapstone – type 2 is urgent. Soapstone – type 3,used for stone replacement, has suffered damages,too. Low number and small size of the soapstonepieces do not allow the reliable rating of theirweathering susceptibility.

3.5. Minster St. Quirin in Neuss / Germany

The use of damage indices for The judgement ofrestoration measures is presented for the MinsterSt. Quirin in Neuss/Germany (Fig. 15). The lateRomanic basilica dates back to the beginning of the13th century. Several times parts of the monumentwere destroyed by war or fire. Due to restorationactivities in the past, many stone types like differentvarieties of volcanic tuff, trachyte, basalt, limestone,sandstone and slate occur.

Extensive studies have been carried out at themonument in order of damage diagnosis andappropriate restoration. The interdisciplinary cooper-ation of scientists, curator, representatives ofmonument authorities, architect, engineers andrestorers has comprised precise damage diagnosis,development of a restoration concept based on thedamage diagnosis, execution and documentation ofrestoration measures, reevaluation after restorationand judgement of restoration measures (Fig. 16).Results of the reevaluation after restoration arenecessary for future restoration activities and main-tenance of the monument. With this step theapproach to effective and economic monumentpreservation is completed.

Figure 15. Minster St. Quirin. Neuss / Germany.

DAMAGE DIAGNOSIS BEFORERESTORATION (D 1)

Stone material, weathering forms,damage categories, damage indices

↓

RESTORATION CONCEPT(Co-operation of scientists, monument owner,

monument authorities, architect, restorers)↓

RESTORATION MEASURES↓

DOCUMENTATION OFRESTORATION MEASURES

↓

REEVALUATION AFTERRESTORATION (D 2)

Stone material, weathering forms,damage categories, damage indices

↓

JUDGEMENT / CERTIFICATIONOF RESTORATION MEASURES(Based on comparison of D 1 and D 2)

Figure 16. Damage diagnosis for monument restoration.

In order to judge resp. certificate restorationmeasures, the state of damage before and afterrestoration has been compared. In a first step ofevaluation, damage categories before and afterrestoration have been considered. In the Figures 17and 18 maps of damage categories before and afterrestoration are presented for a part at the southfacade of the tower. The quantitative evaluation ofdamage categories for this investigation area isshown in Figure 19. The very severe and the severedamages (damage categories 4, 5) and most of themoderate damages (damage category 3) have beenremedied or reduced in the course of restoration.After restoration about two third of the stone surfaceis without visible damages. Damage indices havebeen calculated from proportion of damages cate-gories before and after restoration for conclusivejudgement/certification of the restoration measures.

In Figure 20 damage indices before and afterrestoration are compared. The linear damage indexis taken as example. Compared to damage indicesbefore restoration, a reduction of damage indices upto 80 % can be stated after restoration. Restorationnever will achieve an absolutely damage-free situ-ation. The comparison of damage indices before andafter restoration proves great success of the executedrestoration measures. In a further step of evaluationby means of damage indices it is possible to judgesuccess of restoration measures individually for eachstone type. This is of special importance for allmonuments constructed from stone types withdifferent degradation behaviour.

Figure 17. Map of damage categories before restoration.Minster St. Quirin – Neuss / Germany. Tower – part of thesouth facade.

Figure 18. Map of damage categories after restoration. MinsterSt. Quirin – Neuss / Germany. Tower – part of the southfacade.

0

10

20

30

40

50

60

70

0 1 2 3 4 5

Damage categoriesA

rea-

%

before restoration

after restoration

0 - no visible damages1 - very slight damages2 - slight damages

3 - moderate damages4 - severe damages5 - very severe damages

Figure 19. Damage categories before and after restoration. Partof Minster St. Quirin.

0

1

2

3

4

5

N-4 S-3 W-3 W-4

Investigation areas

Lin

ear

dam

age

ind

ex

before restoration

after restoration

Figure 20. Linear damage index before and after restoration.Minster St. Quirin. Parts of the tower.

4 SUMMARY AND CONCLUSIONS

The monument mapping method has proved to be areliable and efficient phenomenological procedurefor characterisation, documentation, evaluation andrating of stone degradation at monuments. In addi-tion to weathering forms, used for objective andreproducible description of degradation phenomena,and damage categories, used for rating of individualstone damages, damage indices have been estab-lished as very suitable tool for conclusive quanti-tative rating of damages. The consequent use ofweathering forms, damage categories and damageindices can be considered as an advanced approachand essential contribution to well-founded damagediagnosis at stone monuments and to sustainablemonument preservation. The consistent strategy oflinking weathering forms with damage categoriesand damage indices is addressed and recommendedto end-users like:

- organisations, monument authorities or monu-ment owners involved in planning and decisionof monument preservation policies and strate-gies,

- contractors involved in damage diagnosis andmonument preservation activities like architects,engineers, restorers, conservators, consultants,project managers, construction com-panies etc.

Use of damage indices ensures scientific quanti-fication and rating of stone damages for entiremonuments or single structures. Damage indicesallow comparison and ranking of different monu-ments or parts of monuments. Use of damage indicescontributes essentially to rating and comparison ofstone materials regarding their susceptibility todegradation. It enhances risk estimation and itcontributes to risk management. Suitable use ofdamage indices have been presented by means ofexamples.

Damage indices point out need and urgency ofintervention. Damage categories locate those parts ofa monument which intervention has to focus on.Weathering forms have to be considered fordeduction of appropriate types of preservationmeasures. Damage categories and especially damageindices represent very practical tools for reliablejudgement of preservation measures. For regularreevaluation of monuments in the frame of long-term survey and maintenance the consequentapplication of weathering forms, damage categoriesand damage indices is advisable.

5 REFERENCES

Fitzner, B. & Heinrichs, K. 1998a. Damagediagnosis at natural stone monuments – mappingand measurements. Proceedings of the 4th

International Congress on Restoration ofBuildings and Architectural Heritage,July 13-17,1998: 170-172, Centro Internacional para laConservación del Patrimonio, CICOP, Spain.

Fitzner, B. & Heinrichs, K. 1998b. Evaluation ofweathering damages on monuments carved frombedrocks in Petra/Jordan – a research project1996-1999. Annual of the Department ofAntiquities of Jordan, XLII: 341-360, Amman.

Fitzner, B. & Heinrichs, K. 1999. Damage diagnosisand preservation of Petra monuments.Medierranean Magazine: Science, Training andTechnology, No. 1, Special issue “New materialsand methods for the preservation, conservationand restoration of the Mediterranean culturalheritage and the development of an innovativeenvironmental friendly form of tourism“ (ExpertSeminar in Naples, 24-25 April 1998): 13-16,Naples: Italian National Research Council –Office for Scientific and Technological Cooper-ation with Mediterranean Countries.

Fitzner, B., Heinrichs, K. & Kownatzki, R. 1995.Weathering forms – classification and mapping.Denkmalpflege und Naturwissenschaft, Natur-steinkonservierung I: 41-88, Berlin: Verlag Ernst& Sohn.

Fitzner, B., Heinrichs, K. & Kownatzki, R. 1997.Weathering forms at natural stone monuments –classification, mapping and evaluation. Inter-national Journal for Restoration of Buildings andMonuments, Vol. 3, No. 2: 105-124, Stuttgart:Aedificatio Verlag / Fraunhofer IRB Verlag.

Fitzner, B., Heinrichs, K. & Volker,, M. 1997a.Monument mapping – a contribution to monu-ment preservation. In F. Zezza. (ed), Proceedingsof the E.C. Research Workshop “Origin, mecha-nisms and effects of salts on degradation ofmonuments in marine and continental environ-ment“, March 25-27, 1996, Bari (Italy): 347-355,Bari: C.U.M. University School of MonumentConservation.

Fitzner, B., Heinrichs, K. & Volker,, M. 1997b.Model for salt weathering at Maltese Globigerinalimestones. In F. Zezza (ed), Proceedings of theE.C. Research Workshop “Origin, mechanismsand effects of salts on degradation of monumentsin marine and continental environment“, March25-27, 1996, Bari (Italy): 333-344, Bari: C.U.M.University School of Monument Conservation.

Fitzner, B. & Kownatzki, R. 1997. Erfahrungen mitder Kartierung von Verwitterungsformen anNatursteinbauwerken. In W. Leschnik & H.Venzmer (eds), Bauwerksdiagnostik und Quali-

tätsbewertung, WTA-Schriftenreihe, Heft 13: 157-172, Stuttgart: Fraunhofer IRB Verlag.

Heinrichs, K. & Fitzner, B. 1999. Comprehensivecharacterization and rating of weathering state atmonuments carved from bedrocks in Petra/Jordan– Weathering forms, damage categories anddamage index. Annual of the Department ofAntiquities of Jordan, XLIII: 321-351, Amman.

Heinrichs, K. & Fitzner, B. 2000. Deterioration ofrock monuments in Petra/Jordan. Proceedings ofthe 9th International Congress on the Deterio-ration and Conservation of Stone, 19-24 June2000, Venice – Italy, Volume 2: 53-61, Amster-am: Elsevier.

Kownatzki, R. 1997. Verwitterungszustands-erfassung von Natursteinbauwerken unter be-onderer Berücksichtigung phänomenologischerVerfahren. Dissertation RWTH Aachen, AachenerGeowissenschaftliche Beiträge, Band 22, Aachen:Verlag der Augustinus Buch-handlung.

Kownatzki, R. & Fitzner, B. 1999. Verwitterungs-zustandserfassung an Natursteinbauwerken. Zeit-schrift der deutschen geologischen Gesellschaft,150/3: 543-564, Stuttgart: E. Schweizerbart´scheVerlagsbuchhandlung.