How to build safe roofs with corrugated galvanized iron (CGI) sheeting ifrc-sru.org Shelter Research Unit Innovating shelter HOW TO BUILD SAFE ROOFS WITH COrrUGATED GALVANIZED IRON (CGI) SHEETING IMPORTANT NOTICE T he information provided in this manual and the calculations are based on up to date material specifications, field testing and current practice of calculating structures (using Eurocodes 1, 3 and 5) and must be treated as guidelines only and evaluated for suitability in the context of specific local conditions. Risk is inherent in construc- tion and especially after natural disaster caution must be exercised so as not to increase the threat to disaster affected persons. Users of this manual do so solely at their own risk. The International Federation of the Red Cross and Red Crescent societies – Shelter Research Unit (IFRC-SRU) nor any of it’s employees or technical consultants assume any liability for damages, loss or claims, of any nature, including the death or injury of persons or property damage, associated with the use of or reliance upon information contained in this manual. This publication has been made possible through the generous support of: Belgian Red Cross, Flemish and French speaking communities: Contents T ABLE OF CONTENTS Acknowledgements 11 Foreword 13 About this manual 14 Structure of the manual 15 For whom is this manual? 16 Technical terms used in this manual 17 Glossary of Terms (Alphabetical) 23 Acronyms 26 SECTION A Materials 29 A.1 Corrugated Roofing Materials 29 A.2 Corrugated Galvanized Iron or Steel (CGI) sheets 32 A.2.1. Dimensions and measurement for CGI sheets 33 A.2.2. Type of Galvanization or Coating 36 Advantages and disadvantages of each type of coating: 38 A.2.3 Coating thickness and service life for CGI sheets 39 A.2.4. Example Technical specifications for CGI sheets 48 A.2.5. Problems with CGI sheets and preventive measures 50 Corrosion 50 Measures to avoid corrosion problems: 52 Mechanical and physical deteriorations: 52 Fixings / fasteners failure: 53 A.3 Materials for the structural support of CGI roofs 54 A.3.1. Lumber / Timber 55 A.3.2. Coconut wood (coco lumber) 62 A.3.3. Bamboo 67 A.3.4. Metal 68 A.3.5. Advantages and disadvantages of each type of support 69 A.4 Fixings / fasteners and accessories 71 A.4.1. Roofing nails 72 Example technical specifications of roofing nails for CGI sheets 74 A.4.2. Roofing screws 75 A.4.3. Particular fixings for Metal and Bamboo 79 A.4.4. Sealing washers 81 A.5 Performance testing of fixings and supports conducted by IFRC-SRU 84 Comparative overview of roofing nails and roofing screws based on evidence from IFRC – SRU testing 89 A.6 Hurricane straps / ties 91 A.6.1. Coiled strap 92 Contents A 6.2. Hurricane straps to connect laths/battens to rafters 94 A.6.3. Hurricane straps to connect rafters to wall plates 96 A.6.4. Fasteners for hurricane straps and coiled straps 99 A.7 Roofing accessories: ridge capping and fascia capping 101 A.7.1. Ridge cap and hip cap 101 Example Technical specifications: Ridge cap (extract from the Emergency Items Catalogue) 103 A.7.2. Fascia / verge cap or bargeboard flashing 104 Practical Summary Section A 106 CGI sheets and accessories 106 Supports for CGI sheets: lumber / timber, coconut lumber, bamboo and metal: 111 SECTION B Quality control, transportation and storage, basic safety equipment 112 B.1 Basic safety equipment 112 B.2 Quality control of the CGI sheet and other galvanized items 114 B.2.1. Tests to verify the dimensions of the CGI sheet 115 B.2.2. Tests to verify the thickness of the zinc coating 117 B.2.3. Tests to verify the quality of the zinc coating 124 B.3 Transportation and storage 126 B.3.1. CGI sheets and other galvanized roof covering items 126 B.3.2. Lumber / timber, coconut wood and bamboo 129 Practical Summary Section B 131 SECTION C Roof shape and pitch 132 C.1 Effects of wind and earthquakes on structures 132 C.1.1. General effects of strong winds and earthquakes on structures 132 C.1.2. Effects of wind on structures 134 C.2 Wind pressure on walls for different shelter configurations 136 C.2.1. Wind pressure on walls 136 C.2.2. “Closed” shelter 137 C.2.3. “Open” shelter 138 C.2.4. Shelter elevated from the ground 139 C.3 Impact of wind pressure on different types of roofs 140 C.3.1. Cyclone categories and sustained wind speed 141 C.3.2. Exposure or Type of Terrain 143 C.3.3. Best orientation of shelter and roof 145 C.3.4. Advantages and disadvantages of the different roof shapes 146 C.3.5. Pitch of the roof 148 C.3.6 Roof Details 150 C.4 Choice of roof shape and pitch depending on the exposure (type of terrain) and wind speed 157 C.4.1. Urban area 159 C.4.2. Suburban and rural areas with cover of vegetation 162 7 Contents C.4.3. Rural area with low vegetation 166 C.4.4. Coastal area 170 Practical Summary Section C 174 SECTION D Installation guidelines 178 D.1 Useful tools to cover the roof with CGI sheets 179 D.2 CGI sheet layout 180 D.2.1. Layout of full-length CGI sheets per slope 180 D.2.2. Layout of more than one CGI sheet per slope 182 D.2.3. Overlaps and overhang 184 D.3 Fixings / fasteners 188 D.4 Installation details 191 D.4.1. Laths / battens / purlins 191 D.4.2. Eaves’ overhang 193 D.4.3. Edges / verges 196 D.4.4. Ridge caps 200 D.4.5. Hip details (hipped roofs) 203 D.4.6. Roof end for single-pitch roofs 204 D.5 Comparison of exemplary case study calculations 205 D.5.1. Suburban or rural area with cover of vegetation 207 D.5.2. Rural area with low vegetation 212 D.5.3. Coastal area 215 Practical Summary Section D 218 SECTION E Roof maintenance and mitigation measures 220 E.1 Roof maintenance 221 E.1.1. Laths / battens and other structural elements 221 E.1.2. CGI sheets 221 E.1.3. Fixings of the CGI sheets 223 E.1.4. Hurricane straps / ties and their fixings 225 E.1.5. Check the gutters 225 E.2 Mitigation measures 226 E.2.1. Shelter with outside walls that are not airtight 226 E.2.2. Shelter with airtight walls: 227 E.2.3. Reinforcement measures to hold the roof covering in place 229 E.2.4 Types of anchors 237 Practical Summary Section E 240 8 Contents A NNEX (You will find the Annexes online under the provided links) Annex 1 – Galvanized steel sheet conversion table.pdf http://ifrc-sru.org/annex_1/ Annex 2 – Conversion tables for roofing nails and screws.pdf http://ifrc-sru.org/annex_2/ Annex 3 – defining Cyclone categories according to sustained wind speed.pdf http://ifrc-sru.org/annex_3/ Annex 4 – Basic wind speed in various countries.pdf http://ifrc-sru.org/annex_4/ Annex 5 – Explanations for the Roof Estimate Form.pdf http://ifrc-sru.org/annex_5/ Annex 6 – Basic pitch of the roof in degree, percentage and dimensions http://ifrc-sru.org/annex_6/ Annex 7 – Roof Estimate Form 2017.02.15 http://ifrc-sru.org/annex_7/ Annex 8 – Library & further reading http://ifrc-sru.org/annex_8/ 9 A CKNOWLEDGEMENTS Project coordination and editing of manual: Cecilia Braedt (IFRC-SRU) Lead author: Emeline Decoray (Shelter over^head) Laboratory and field tests by: Daniel Ledesma (IFRC-SRU) Graphic design by: Teresa Boese (titrobonbon.de) Photos: Emeline Decoray (Shelter over^head) and IFRC-SRU Cover Photo: Emeline Decoray (Shelter over^head) and St Vincent and the Grenadines Red Cross Special thanks to ICRC delegation Philippines particularly the Samar delegation for providing operational support and making their warehouse grounds in Samar avail- able for the field testing. Special thanks to Gafur M Nur Abdul, Britt Christiaens and Marco Alberti. Furthermore IFRC delegation Philippines, Wardell Eastwood, and the IFRC and Philippines Red Cross in Tacloban for facilitation and operational support. Ing. Jean Lamesch for sharing his extensive expert knowledge on CGI sheet and zinc coating. Additional thanks to Alexander van Leersum (Netherlands RC), Azmat Ulla (IFRC), Charles Aurouet (French RC), Corinne Tréherne (IFRC), David Dalgado (IFRC), Ela Serdaroglu (IFRC), Leeanne Marshall (IFRC / Australian RC), Nadine Weber (Swiss Red Cross), Patrick Elliot (IFRC / British RC) Santiago de Luengo (IFRC / Mexican Red Cross), and Wardell Eastwood (IFRC) for peer review and valuable feedback and David Dalgado (IFRC) for final proof reading. 11 F OREWORD The World Disaster Report 20161 statistics of the last 10 years show that storms rank second, after earthquakes, in causing loss of lives and damage to property. Storms are also the natural disaster that, after floods, affects the highest number of people worldwide. Pictures of the devastation after Typhoons, Cyclones or Hurricanes tell a clear story about the effects of such extreme weather events. Roofs torn off or huts and houses even completely overturned or destroyed by the impact of the winds. Of course this destruction affects mostly the poorly built structures that are con- structed without much technical expertise or with low quality construction materials. However, low-cost construction does not have to result in poor performance. Most local building cultures in contexts that have been confronted with natural disasters like storms as long as anyone can remember, have developed techniques to build structures that resist the common disasters, using locally available, often natural materials.