Repair of Historic Timber Structures, Second Edition

Contents Preface vii
Acknowledgements ix
01 Introduction: Initial considerations 1
Purpose 1
The overall process 2
Conservation standards 4
Medical analogy 4
Differences from new build 7
Design codes 8
The structure of the text 8
Definition of terms 9
References 10
02 Structures and materials 11
Introduction 11
Pre-fire structures 11
Post-fire structures 18
Timber 26
Iron 30
Roofing materials 30
References 31
03 The form and behaviour of historic joints 33
Introduction 33
Mortice and tenon 33
Notched joints 41
Scarf and bridle joints 42
The half lap 43
Joints in tension and moments on joints 43
Ironwork 44
References 48
04 The survey 49
Preliminary survey 50
Detailed survey 53
Common types of distress 55
Equipment 57
References 59
05 Structural behaviour 61
A cautionary tale 61
ISCARSAH Recommendations 62
Force of habit 64
Joint behaviour 65
Loads 65
References 83
06 The strength of timber 85
Early understanding 87
Grading methods – knots 88
Other factors 93
Moisture content 95
A practical example 97
Conclusions 98
References 99
07 Intervention strategy 101
The structural report 101
Historic character 102
Original structural scheme? 103
To dismantle or not? 105
Earlier repairs 106
Reliance of the carpenter 106
References 107
08 Decay and repair 109
Classification of repairs 109
Design codes 109
Mechanical fasteners 110
Adhesive bonded reinforcement 118
Timber replacements 119
A patch at a mortice 119
Refacing of a member in bending 121
New beam ends 121
Strengthening members in bending 128
Provision of supplementary structure 129
References 131
09 Case studies 133
A purlin failure 133
St Mary-at-Hill 135
An A-frame roof 138
Trinity College Gate 140
References 143

Bibliography 145

Appendix – Hankinson’s formula 149

Index 151