Soiling and Cleaning of Building Fa~ades Soiling and Cleaning of Building Fa~ades Report ofTechnical Committee 62 SCF RILEM (TheInternationalUnionofTestingandResearchLaboratories for Materials andStructures) Editedby L.G.W. Verhoef @ Taylor& Francis ~ Taylor&FrancisGroup LONDONANDNEWYORK Firstpublishedin1988by Taylor& Francis 2ParkSquare, MiltonPark,Abingdon, Oxon, OX144RN PublishedintheUSAby Taylor& Francis 270MadisonAve, NewYorkNY 10016 TransferredtoDigitalPrinting2005 @ 1988RILEM ISBN0412306700 Allrightsreserved. Nopartofthisbookmay bereprinted,orreproducedorutilizedinany formorbyanyelectronic,mechanicalorother means,nowknownorhereafterinvented, includingphotocopyingandrecording,orin anyinformationstorageandretrievalsystem, withoutpermissioninwritingfromthe publisher. BritishLibraryCataloguinginPublicationData Soilingandcleaningofbuildingfa<;ades. 1.Buildings.Exteriors.Cleaning I.Verhoef,L.G.W.(LeoG.W.) 690'.24 ISBN0-412-30670-0 LibraryofCongressCataloginginPublicationData InternationalUnionofTestingandResearch LaboratoriesforMaterialsandStructures. TechnicalCommittee62SCF. Soilingandcleaningofbuildingfacades : reportoftheTechnicalCommittee62SCF, RILEM(theInternationalUnionofTesting andResearchLaboratoriesforMaterials andStructures)/ editedbyL.G.W.Verhoef. p. cm. Bibliography:p. Includesindex. ISBN0-412-30670-0 1. Exteriorwalls-Cleaning. 2. Weatheringof buildings. 3. Buildingmaterials Cleaning. I. Verhoef,L.G.W. II. Title. TH2235.I581988 648'.5-dcI9 88-11823 Contents MembersofTechnicalCommittee62 Vll Acknowledgements IX Introduction xi 1 Theskinofthefacade 1 1.1 Theskinofconcrete 2 1.2 Theskinofstonesandbricks 8 1.3 Theskinofwood 10 1.4 Theskinofglass 12 1.5 Theskinofplasticbuildingcomponents 14 1.6 Theskinofmetals 15 2 Changesintheappearanceoftheskinofthefacade 18 2.1 Introduction 18 2.2 Changescausedbyatmosph ericconstituents 18 2.3 Changesofaspectsoffacadesduetoparticularsubstances presentinbuildingmaterials 49 2.4 Facadealterationscausedbyadjacentandadditionalmaterials 51 2.5 Changesbysoiling 58 3 Non-biologicalsoiling 65 3.1 Airborneparticulatematteranditsmeasurementrelevant tothesoilingoffacades 65 3.2 Transferenceofatmosphericpollutiontothefacade 83 3.3 Attachmentofparticlestothefacade 92 3.4 Rainfallrun-off 98 4 Biologicalsoiling 111 4.1 Introduction 111 4.2 Viableparticlesintheair 112 4.3 Conditionsformicroorganismdevelopment 115 4.4 Effectsofmicroorganismsonsubstrates 117 v 5 Cleaningofsoiledfa~ades 124 5.1 Introduction 124 5.2 Somephysicalprinciplesofcleaning 126 5.3 Cleaningmethods 127 5.4 Problemsinvolvedinthetreatmentofsoilingofbiological origin 132 6 Recommendationsfordesignofbuildingfa~ades 136 6.1 Introduction 136 6.2 Thesituation(location) 136 6.3 Fa~adematerial 138 6.4 Theprofilingoftheform andthedetailingofbuildings 140 Appendix 1 Thesandblasttestasamethodtojudgetheproperties ofthesurface 155 Appendix2 Testresultsofthe'soft'sandblastmethod 157 Appendix3 Amethodfordeterminingthesoilingcapacityofair 162 Appendix4 Testresultsofthereflectancemeasurements 165 Appendix5 Testmethodsonbiologicalsoiling 172 Appendix6 Outdoorexposuretestsofatmosphericsoiling 174 Appendix7 Waterabsorptiontest 178 Index 185 vi Members of Technical Committee 62 Soiling and Cleaning of Building Fa~ades ThelateProfessorE.M.Theissing (Chairman) F. HawesDipArchRIBA SeniorAdvisoryArchitect CementandConcreteAssociation Slough UnitedKingdom ].M.Estoup IngenieurCNAM Centred'EtudesetdeRecherchesdel'industrieduBetonManufacture (CERIB) Epernon France A. Perrichet DocteurIngenieur LaboratoiredeGeomechaniqueThermiqueetMateriaux InstitutNationaldesSciencesAppliquees RennesCedex France UlrichTriib ArbeitsleiterTechnischForschungsundBeratungsstellederSchweizCement Industrie Wildegg Switzerland Vll K.L.Pwa (SecretaryuntilSeptember 1985) SeniorLecturer GroupMaterialsandConstructions DepartmentofCivilEngineering TechnicalUniversityDelft TheNetherlands C.A. Kortland (Secretaryfrom September 1985) SeniorResearchEngineer CentralLaboratoryBredero Maarssen TheNetherlands L.G.W. Verhoef SeniorLecturerinRenovationandMaintenanceTechniques DepartmentofArchitecture TechnicalUniversityDelft TheNetherlands VIll Acknowledgements Contributions have also been received from specialists outside the committee andtheir assistance isgratefully acknowledged: o. Beyer Msc., Project Leader ofthe Cement-Och-Betong-Instituet, Stock holm, providedthe sections onrainfall run-off. Dr R.D. Degeimbre, Senior Lecturer of the Liege University in Belgium, providedthe sections onthe skin andweatheringofplastic. Dr P. Rossi-Doria, CNR Centro 'Conservazione Opere d'Arte', Italy, providedthe sections onthe skin andweatheringofstones andbricks. Dr ].F. van de Vaate, Scientific Director of the Dutch Energy Research Foundation, provided the section on airborne particulate matter and its measurements relevantto the soilingoffa~ades. M.W. Verver, ofthe Materials and Constructions Group, Delft University of Technology, providedthe sectionsonthe skin andweatheringofwood. Professor H. de Waal and N. van Santen, ofthe Institute ofApplied Physics TNO-TH glass department provided the sections on the skin and weathering ofglass. Professor ].H.W. de Wit, Delft University of Technology, provided the sectionsonthe skin andweatheringofmetals. Mrs Willy Harkema-Louw and Mrs Martha Betten-Venhuizen of Bouw centrumTechnology, Maarssen, preparedthefinal typescript. The help of Dr Sjef Schoorl from the applied linguistics department, Delft University of Technology, is acknowledged for his valiant attempts at bridging the larger gaps between the language used in the manuscript and standard English. Thanks are also due to Mr Michael Dunn, Ms Madeleine Metcalfe andthe editorialandproductionstaffofChapmanandHallfor their assistance. IX Introduction Rilem Technical Committee 62 SCF was formed under the chairmanship of the late Professor Eric Theissing to study the soiling and cleaning ofbuilding fa~ades. In order to make useful recommendations for suitable methods of cleaning, itwasnecessarytoinvestigatethe complexsystembywhichsurfaces are changedbythe natural and unnaturalelementsinthe environment. Some ofthese changes are physical and others superficial but all need to be under stood. Itis necessaryto studythewaysinwhichpollutioninthe atmosphereis transportedto buildings and adheresto surfaces, andthemannerinwhichthe dirt can subsequently be redistributed by water on the fa~ade. This redistri bution of the dirt is normal.1y responsible for the most noticeable visual changes, so the movement ofwind around buildings and its influence on the quantities ofrain which hit different parts ofthe various fa~ades also forms part ofthe study. Dirt affects fa~ades in a number of ways. Some types of soiling can physically damage certain types ofsurface but in many cases there is only a visual change. Some materials, because oftheir colour or texture, can look acceptable in spite ofbeing dirty w hile others only look right when they are clean. However, visual changes are sometimes so great as to have an adverse effect on the value ofa building. These phenomena are therefore worthy of study so that they can be anticipated by the architect and taken into account at the time thatthe buildingis designed. Buildings can be designed to minimize dirtying, but the study ofrain and wind movements around buildings shows that in most cases it is impossible to ensure that all parts of all fa~ades receive enough rainwater to keep them clean unless the building can be designed in a form resembling a pyramid. It would be quite absurd to suggest that all large buildings should be pyramid shapedsowe areforced to acceptthat some parts ofsuchbuildingswillnotbe naturally cleaned. The architect may decide, by choice ofmaterials and by providing access, to make these parts ofthe building easy to clean, but there is another option. This is to accept that these areas will remain dirty and, by careful choice of materials and details, the architectcan attemptto ensurethatthebuildingcan carry this dirt without being physically or visually harmed. Many ofthe old buildings in our towns and cities are in this state ofbeing partly clean and Xl