table of contents 3912

7/28/2019 Table of Contents 3912

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Cracking and Building Movement

byPeter R. Dickinson

FRIes, FC I Arb

chapter on MOllitorillg byNigel Thornton

BSc (Hons), C Eng, ~ I I C E , MI HT, FGS

12905711111111

, .....' \ RICS\ ~ BOOKS


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Contents

Preface

WHY HAS CRACKING BECOME IMPORTANT?IntroductionWhy is cracking now so prevalent?

InsuranceClimate changeChanges in industrial and building materialsProfessional Indemnity Insurance

2 WHY BUILDINGS MOVE - AN OVERVIEWIntroductionBuilding movement which results from conditions below ground

Settlement of foundationsSubsidence of foundat ionsUndermining of foundat ionsConsolidation of fill below foundations or floorsChemical attack

Building movement which results from conditions above groundThe use of'green' materialsCentral heatingMovement due to inadequate designFaulty construction, alteration and/or repairOverloading and over stressingChemical reactionMaterial deterioration-Iemperature changesNatural drying of the structure and finishes

3 TYPES OF MOVEMENTExpansion and shrinkage

Clay brickworkConcrete blockworkCalcium silicateNatural stoneReinforced concreteMass concrete and renderTimber

Moisture/thermal movementMoisture/thermal movement of day bricksMoisture/thermal movement in concrete blockworkMoisture/thermal movement in calcium silicate bricks

1122

35556667777788888

I II II II II II II II II I121313

ii i


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Cmc/,;itrji dlld Iluildill}; MovE'mnrl

Moisture/thermal movement in concrete and render 18l-o loisture movement in mortars 19l-oloisture/thcrmal movement in timber 19Moi!>ture/thermal movement in roofs 19

4 CHANGES DUE TO CHEMICAL ACTIONSulphate altack 23Rendering 24Ground-bearing slabs 24Foundations 25Co rrosion 25In cavity walls 25Carbona tion 25Alkali-silicate reaction 25

5 STRUCTURAL MOVEMENT - A DETAILED STUDYSettlement 27Foundation subsidence 27Shrinkage of day subsoils 27Clay heave 30Foundation undermining 32Mining operations 32Leaking drains or the presence of land drains 32

6 THE EFFECTS OF MOISTURE AND TREESThe effect of moisture on day subsoils 35The Clay Plasticity Index 36The effecl of trees on day subsoils 36How trees damage buildings 36Me thods of tree risk assessment 37Worked example 40

7 CONTRACT UAL MATTERS'lak ing enquiries 45Creating the Contract 45The Contract 45The Offer 45The Acceptance 45The Performance is carried out by both parties 45The Terms of the Contract 46The Contract in writing 46Standard Terms and Cond itions 46The Misrepresetltatioll Act 1967 46The Unfair Cotltract Terms Act 1977 46The Unfair Terms ill Consumer Collfracts Regulations 1999 47The practice of creating a Contract 47The Building Contract 47Wha t to do about specialists! 48'10 whom can the specialist be made respons ible? 48The Constructioll (Design and Managem ent) Regula /ions 1994 48Par ty Wall etc. Act 1996 49Housillg Grallts, COllstrtlctioll a1ld Regeneratio1l Act 1996 50

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8 INSPECT ION AND RECORDING DEFECTSSymptomsGathering the informationThe site inspectionInspection of the propertyStart where the crack has been identified

Record the general site characteristicsSketching and measurement of cracksBasis for development of an inspection recordFurther investigationsDetermine the age of the crack

Recording variations in levelRecording movement in leaning wallsThe acceptable degree of tiltDrain te:.l:.Identification of the soil type and the type of tree

9 ASSESSI NG THE DAMAGEIntroductionAssessing the damage

What is the cause of the damage?Is it likely 10 get worse? If so how quickly?Landslip riskFa iling retaining wallsLeaking drains

Recognit ion and assessment of heave damageRecognition and assessment of subsidence movementIndicators of subsidenceAssessment of crackingRepairing the damageWhat if foundation movement is the cause?What if tree roots are decided to be the cause of the damage?Solutions to tree root problemsAssessment of cracking and corrosion in concreteCorrosion of reinforcementHigh Alumina Cement (HAC)

Crackillg and Buildiug Movelllelll

515152525355555758595960606062

Recognition and assessment of non-subsidence, non-heave structural movement

656666666767676768686868697071171727373

10 MONITORING OF CRACK AN D MOVEMENT DAMAGERequirement for and frequency of monitoringPositioning of crack monitoring devicesMethods of crack monitoring

The two dot methodGlass tell talesPlastic sl iding platesThe three screws methodPresentation of results and interpretation of dataTwo screw methodLevel monitoringPrecise levelling equipmentSample calculations

777777777878788080808184


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11 THE REPORTThe front coverAn indexFirst pageTechnical investigationAssumptions madeConclusions and recommendationsSignatureAppcndice:,CopiesLayout of the report

12 HISTORY OF BUILDING AND REPAIRSAn overview

Kc)' evenlS and legislationTypical 'period' defects which might be expected

13 SPECIFICATIONS AND SCHEDULESSpecificationsSchedules of Condition or DilapidationsSchedules of ConditionSchedules of Dilapidation

14 SPECIFYING THE REPAIRSChemical reactions

CorrosionSulphate attackAlkali-silicate reactionjlaio substructure repairsTypical underpinning specificationsTypical underpinning specification clauses

Superstructure repairs and typical specificationsRepoinlingRepair ofdamaged brickwork - to rebuild or nOllO rebuild?Floor repairs - solid floorsFloor repairs - timber f l o o r ~Thermal crackingRoof spreadListed buildings and heritage issuesQuestions to ask when designing extension foundations

15 SUPERVISION OF BUILDING WORKSSite inspectionInslruction bookDealing with site personnelSupervision of building works - checklists

, i

8989909Q919191919191

939496

97989899

101101102103103105108112112112114115117130151151

153154154155


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APPENDIX A, CRACK DIAGNOSISTable J: Crack diagnosisTable K: Testing the evidenceTable L: Movements an d principle causesTable M: Latent defects indicated by pattern of occurrenceProperty inspec tion recordFormat for a report

APPENDIX B, MATERIALS REFERENCESTable N: Thermal expansion coefficientsTable 0: Propor t ions of render mixesTable P: Render mixes'lable Q: Mortar mixes

APPENDIX C, USEFUL ADDRESSES AN D WEBSITES

APPENDIX D, CD CONTENTS AND USER GUIDE

FURTHER READING

INDEX

CD LICENCE

CrackingmId Building Afllv('IIt('/U

165167168169171173

175177178179

ISI

185

187

191

198


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Index

aJJrn,c ,useful 111 1

age of crackJelnmillalion 59

alkali-silicaI


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lndC"l(

cla)' )ubwih(racking duC" to ".'a$Onal 1II0l"t'IIIl'nt 6ifoundation subsidence 5

shrinkage of clay ) u h ~ o i l , 2imoisture, eff('


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embedded stcd and ironc o r r o ~ i o n 74

cau ... 101repair 101~ y m p l o m s 10!

c n ' i u I T l t ' ~conlr,l(t following S f ( contractstaking 45excal-ationchecklist 155

expansion and ,hrinkage 11a s s e ~ s i n g damage 66calcium silicate brich 11clay hrickwork IICOllCrctl' blockwork 11

m a ~ ~ concrete and render I1natur,11 stone 11OH'r lintols, ' a u s e ~ 118repair 118

s } ' m p t o m ~ 118reiniorccd concrete 11timhC'r I I

e X l e n ~ i O I l \

fill

cracking ,Itcauses 146repair 148symptoms I

foundations, e ~ i g n i n g 151

consolidation SfI' c o n ~ o l i d a t i o n of tillfoundation subsidence S

llank waU movementcau!>C) 122repair

summary 126ties at cornas and junctions 126tymg 125,126

symptoms 112flat roof, Se t roofingMoor repairs

,olid floors 11-4map-pattern (falking 11-4sloping floon I J.Istraight-line cracking 114untied precast concrete flOOh 114

timher fluorshouncyJ1oors 115..agsingfloors 116

MOClrscunwlidation of fill 6ground-bearing ,lab)

seltlcment 27sulphate attack 24

r e p a i r ~ sce fluor repairssettlement 27

foundation,con"(llidalion of fill 6e x t e n , i o n ~ , designing IS ImO\'


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Index

defo;'din' !into! and arch 119e c ~ e n t r i c loading on lintols 146~ h r i n k a g e or expansion o\'o;'r linto! 118

~ r m p l o m sarch repairs 119dehtil' t ' !intul and arch 119t'(:centric loading on lintols 146~ h r i n k a g e or expansion 01 er linlol lI S

l i ~ w d buildingsrepairs 151stonework 151

map-pattern ctacking 4rendering 18solid !loor)

c a u ~ c ~ 114repair 114symptoms 114mass concrett',ff O I K r c t cmining

foundation ~ u b s i d e n c e 6foundation undermining 6,32Misprl'Sl'l1IaJio"Ad 1967 -16moisturo;'dap u b ~ ( ) i l " effect on 35demand, trees J8

m o i ~ l u r e / t h e r m a l mowment 1Icalcium i l i ~ a \ e brkh I Jday brich 12concrete and render 18concrete block work I Jexpansion/contraction 71methods of controlling thermal mowmcnt 16, 17moisture movement In mortar, 19roofs 19-21

metal cOl'erlllgs 19ripples and blisters 19timber 19monitoring damagelevd moni toring 110

precise levelling equipment 81methodsglass tell tales 78pla)ti, )liding plJI" 711

p r e ~ l ' n t a t i o n of e ~ u l t s and interpretation of dala 80three c r e w ~ 711111'0 dot method 77two serew 80

positioning of devlte) 77requirem('nt for and frequency of 77mortarcement mortar 2lime mortar 2mixes,tableQ 179moisture mOI'('ment 19rcpointing 112,1\3

mOl'emellt 3

194

central heating 7chemical attack 6chemical reaction Rexpan)ion SN! expansion and shrinkagefaulty comtruction, alteration and/or rep;lir 7

j J o o r ~ , consolidation of lill 6fuundations

consolidation of fill 6repairing the damage 69settlemo;'nt 5subsidence 5undermining 6

grt'('n materials , uS(' of 7inadequate design, x a m r l e ~ 7material deterioration Smoisture/thermal movemem sce m o i ~ t u r c / t h e r m a l mO\'ementmonitoring damage ~ monitoring damagenatural drying of Mructure and tillishes 8O\'erloading o\cr 'tre,sing &~ h r i n k a g e SI'I' e x p a n ~ i o n and h r m k a g e

~ t r u c t u r a l Sl.'1! structural movementtemperature changes 8t y ~ ' ~ see expansion and h r i n k a p : ; moisture/thermalmovement

m o v e m t ' n t ~ and principle cauS('stabl . l 16Rnatural stone

expansion and ~ h r i n k a g c 11NH RC tree root 'radii' 3&non-subsidence or non-h('ave o;tructural mo\"ementrecognition ;lIld a ~ s e s ~ m t ' n t 73hulging walls 7-\

calcium silicate bricb Hc o r r o ~ i o n of emblded steel 74lack of lateral restraint 7-1lintol failure 7-1poor c ~ i g n and/or inade\1uate construction 75retain ing wall failure 7-1roof spread i5rot in built-in timbcT'> i5


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principle o n t r a c t o r ~duties -19p r o f e s ~ i ( l n a l indemnity in:>uT.lIlCC 2pmpcriyinspe..::tion 51futTher im'e,tigalions 58acceplable degree of tilt 6U,Ige of crack, dt'lt'rminalion 59

drain t e s t ~ 60movement in leaning walls. recording 60wilt)'pe and type, idcnliti(ation 62,'ariatiom in le'el. e c o r d i n ~ 59gathering information 51record 171derelopmcnt of 5isite i n ~ p c c t i o n 52.153

i n ~ p e c t i o n of propert}' 52recording general site ( h a r a d ~ r i s t i c ~ 55sketching and l l l e a ~ u r e m e l 1 t of cratks 55~ t a r t i n g where crack has be.:'n idcntified 53

~ y m p t o m s 51rear a d d i t i o n ~cra(kingcauses 132rcpair 132,}'mptorllS 131roof spread or subsidence

c a u ' C ~ 131repair 137s y m p t o m ~ 131

recordsproperty inspection 57,171reinforced cOllcrdeexpan\ion and shrinkage 11moi,tur .Jlh . rmal mo,ement 18rendering

damaged. r"pair 11-1e x p a n ~ i o n and ,hrinkage 1Imap-pattern cra(king 18mixesproportions. table 0 177table P 178moi,tun:/therma\ movcment 111 ' m p t o m , \01repairschemical r .actionsalkali-silicate reaction 103corrmion Sft' corro 19ripples and blisters 19~ p r e a d Sec' roof spread

tTU"SCS sce gables and roof trusseswl1hout parapets. thermal crackingcauses I I Irepair 122symptoms 122roof spread 75':aUsesbay windows 1-12chimney breasts. remo,-al 1-12cracking at eXlemions 146(Tacking in rear additions 132cracking in rt'ar a d d i t i o n ~ , rool spread or subsidence.ddermination 132

index

([eating openings in internal r a r U 1 i o n ~ . g r o u n d floor 141creating p e n i n g ~ in intt'rnal partition:>, upper floor 1-11e((('ntric loading on linlOls 146kaking lead valleys 138o\'erloading 1-13roof spread or bowing wa\l" determinat ion 131rOiling bonding limbers 146selllement of part a s c m e n t ~ !-I6limhcr roofs 130unbrac.:'d g a b l e ~ and roof trusses 146uncqualloading on centre ,alley 137walls built off floors. first Aoor 139walls built off floors, ground floor !-IOleaking lead valleys. r('tlesign 13A

repairbay windows 113c h i m n e y h r e a ~ t s , r e ! 1 1 o v a ! 112cracking at t'xtensions 148cracking in rear additiom 132cracking in rear additions, roof spread or subsidence,

determination 132creatin)!, openings in internal partitions, ground floor 141creating openinp in internal partitions. uppt"r floor 1-12eccentric loading on l i n t o l ~ 116leaking kad valleys 1311owrloading 143roof p r e a d or bowing walls. deTermination 131rotting bonding i m b e r ~ 1-16selllemt'nt of part a ~ m e n t s 146timber roofs 131unbraced gables and roof r u " c ~ 1-16unequal loading on cenlre valll'Y 137walls built orf Hoors. i { ~ t floor 139walls built off floors. ground tloor \-11

symptom,barwindo\\s 1-12chimnC} breasts, rcmo'-ai 1-12cracking at e;'(tensions 146cracking in rcaT additions 132cracking in rear additions. roof p r e a d or ,ubsidence.

determination 132creating openings in in ternal p'ITtitions. ground floor 111creating openings in intern;\l partitions. upper floor I'lleccentric luading on Iinlob 1-16leaking kad valleys 137overloading 1-13roof sprt'ad or bowing w a l l ~ . d e t e r m i n a t i o n 131roning bonding Timbers \-16senlement of part ba!ot'ments 1-16timher roofs 130unbraced gables and roof r u , ~ ) \-16unequal loading un centr.:' valley lJ iwalls built off floors, first flour 139w a l l ~ huilT off f 1 ( ) o r ~ . ground floor 139

sagging Hoors(auses )16195


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InJt'x

repair \\7\rmptoms 116

; . ( h e J u l e ~ of condition 98S(ht'dulcs of dilapidation 99s e - t ( l ~ m c n t

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parapet cracking 122roofs without a r a p ~ b I : ! ~shrinkage or expamion Ol'er Ilnto\ 118Iherll1;11 expansion cudli.:ienTSlablcN 173Tilt

; I c c e p t a h l ~ degT ..... of 60Tlmbcr SC(' IIlso building material,built-in limb ..rs, rotting i5

l ' x P J n ~ i o n and shrinkage 11I l ( / O r ~ , r"'pairs,er' !loor r.:pa in

m o i ~ t u r e / t h c r m a l m o \ ' ~ m ~ n l 19roofs, spread se(' H/Of ...adtre

table of contents 3912

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