Metal Roofs Damage Assessment. Seminar Handout

Transcription

1 Metal Roofs Damage Assessment Seminar Handout TM

2 Seminar Participants We appreciate your interest and participation in our seminar presentations which have been based on extended research in the industry, analysis, and field examinations. This presentation is provided for educational purposes only. We do not provide testing or evaluation of your understanding of the material presented by written or oral examination. We do not confer or issue written or implied documentation relative to certification of your ability or understanding of the subject matter. Reference to "certification" by Haag Engineering Co. in any form of correspondence, advertisement, or marketing material, either written or oral, is strictly prohibited. Haag Engineering Co. reserves the right to pursue all legal rights to protect against any unauthorized use of our name, trademark, and privileges to the material and its application. --Haag Engineering Co. About Haag Haag is a worldwide diverse firm encompassing forensic engineering, construction consulting, and research and testing. Haag offers outstanding educational programs and publications. Haag handles all aspects of civil, structural, mechanical, electrical, metallurgical, construction defect, slip/fall, and transportation cases. Haag has been in business since 1924 and we continually strive to be the best. Instructor Profile Carlos Lopez, Ph.D, E.I.T. Ph.D. Civil Engineering M.S. Civil Engineering B.S. Civil Engineering Carlos Lopez graduated from University of Florida with a B.S., M.S., and Ph.D. in Civil Engineering. Currently, he is a member of the American Society of Civil Engineering, the American Concrete Institute, and the American Association for Wind Engineering. Carlos has been with Haag Engineering since 2012 and has inspected and assessed damage to hundreds of roofs. His primary areas of consulting are structural evaluations and general damage assessment. Copyright 2014 by Haag Engineering Co. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from Haag Engineering Co., 4949 West Royal Lane, Irving, TX i -

3 1 Metal Roofing References NRCA (National Roofing Contractors Association) 2 Metal Roofs Damage Assessment Metal Roofing References MBMA (Metal Building Manufacturers Association) 3 Topics: 1. Product description and manufacturing 2. Installation and roof details 3. Problems manufacturing, design/installation, weathering, and mechanical 4. Damage assessment hail and wind 5. Repair methods 4 5 Advantages of metal roofing 6 1. Product description and manufacturing Durable warranties to 50 years Wind resistant Hail resistant (Class 4) Fire resistant Insect resistant Lightweight 100 to 200 lbs/sq (compare asphalt shingles 240 to 400 lbs/sq) 1

4 Disadvantages of metal roofing 7 Types of metals 8 First cost can be high Steeper roofs cannot be walked on Common problems with details at penetrations Can be noisy with changes in temperature, and rain and hail Can be difficult to repair many systems are interlocked 1. Naturally weathering metals 2. Metallic coated steels 3. Protective coatings 1. Naturally weathering metals 9 Copper 10 Aluminum Copper Lead Stainless steel Zinc Copper panels Lead coated copper Terne coated stainless steel (terne is lead and tin, or zinc and tin) A malleable metal that can be formed easily Oxidizes from brown to green colors (patina) over time. Nominal ounces per sq ft The patina of copper over time Metallic coated steels 12 Aluminized steel Aluminum/zinc (Galvalume ) Galvanized steel Terne metal Galvalume -coated steel 2

5 Galvanized steel 13 Galvanized steel 14 The most common coating for steel panels Steel is hot dipped in molten zinc (~1,000 ºF) Zinc is metallurgically bonded to the steel ASTM G60 and G90 applies 0.60 and 0.90 oz. per sq. ft. to the steel (G90 is ~1 mil thick) Zinc is water soluble and sacrificial protection Sometimes distinguished by bold spangle Galvalume coated steel Invented by Bethlehem Steel in 1972 Steel hot dipped in mixture 55% aluminum and 45% zinc Greater corrosion resistance than galvanized Normally bright finish and small spangle Galvalume coated steel Spangle Protective coatings 18 Galvanized Galvalume Fluoropolymer (PVDF: Kynar 500 and Hylar 5000 ) Siliconized acrylic and polyester Pearlescent and metallic additives Clear coat finishes Laminates Anodizing Fluoropolymer paint 3

6 19 20 Paint application Paint application specifics 1. Individual panel spray 2. Continuous coil coat 1. Clean steel remove dirt and oil 2. Chemical conversion (prep) coat 3. Prime coat ~0.25 mil, then heat cure 4. Top coat ~0.75 mil, then heat cure 5. Total paint thickness is ~1 mil Paint application 21 Manufacture of panels Panels from sheets 2. Panels from coil stock Panels from sheets 2. Panels from coil stock Panels bent to form profile in brake Panels are cold formed in a roll former Coil is coated/painted before rolling Panels can be roll formed in a factory or in the field by portable equipment Steel coil is bent to form profile by a series of 20 to 25 dies in a factory; by 7 to 8 dies in the field 4

7 Factory roll former 25 Dies bend coil stock 26 Portable roll former 27 Panel profiles Flat 2. Corrugated 3. Raised rib 4. Standing seam 1. Flat profile Used on flat surfaces, vertical walls, as well as conical or curved surfaces of spires, domes, and cupolas Flat seam Not soldered Soldered 30 5

8 Corrugated profile 3. Raised rib profile 4. Standing seam types 33 Standing seam attachment 34 Fixed clips Expansion (moveable) clips Standing seam installation 35 Mechanically seamed 36 Hand seams Tongs Electrical roll former 6

9 Snap together 37 Types of metal roofing systems Architectural panels 2. Structural panels 3. Metal shingles or shingle panels 1. Architectural panels Structural panels 40 Copper architectural panels 1. Water barrier (hydrostatic) 2. Often slope <3:12 (low slope) 3. Often Standing seams >1 1/2 tall 4. Often Non curing and non skinning sealant (butyl) tape within seams 5. Span between structural supports, normally purlins Structural panels 41 Structural panel seam tape 42 Frames/purlins Painted steel structural panels Butyl tape within standing seam 7

10 3. Metal shingles and shingle panels 43 Paint + granules application Water shedding 2. Slope >3:12 (steep slope) 3. Interlocked or overlapped 4. Applied over structural decking with underlayment 5. Press formed to mimic multiple asphalt or wood shingles, tiles, or slates Steel shingle panel Metal shingles and shingle panels 45 Thinking about metal Expect large expansions or contractions with changes in temperature 46 Thinking about metal Expect oil canning (distortions in the flatness of the metal) Inherent in flat panels 47 Oil Canning Mitigation... Identify problems with coil prior to installation Do not use roofing pans wider than 18 Use heavier gauge metal Use minor ribs or striations in pan profile Use lower gloss finish Apply architectural panels over solid deck rather than over foam insulation or existing roofing materials Account for thermal expansion and contraction Maintain on site roll forming machines in good working condition 48 8

11 49 Architectural panel application Installation and Roof Details Architectural panel valley detail 51 Structural panel application 52 Structural application 53 Structural panel eave detail 54 9

12 Small penetration (soil stack) detail 55 Large penetration (curb) detail 56 Avoid placement in standing seams Drill screws Elastomeric washers form water-tight seal 3. Problems Manufacture, Design, or Installation Galvanized coating problem 59 Too shallow for drainage 60 10

13 Panel slippage due to missing fasteners 61 Screw missing 62 Upslope edge Down slope edge Improper fastener installation 63 Improper fastener installation 64 Over-torqued Skewed Under-driven Missed purlin Over-driven screw Scupper too high (panel closure along eave flooded) 65 Non standard detail 66 11

14 Dead valley 67 Gutter too small 68 Ridge misaligned 69 Non standard termination at vertical projection 70 Counterflashing missing 71 Small penetrations non standard 72 12

15 No flashing at stack penetrations 73 Small penetration details 74 Stack dams runoff Stack does not impede runoff No crickets at large penetrations 75 Large appurtenance not supported by structure below 76 Abutting roof systems require special details Problems Weathering 13

16 Galvanized steel stack corroded away 79 Coating deteriorated 80 Coating deteriorated 81 Environmental problems 82 Acid rain Salt spray Bird droppings Process chemicals Red rust on galvanized steel after zinc is depleted 83 Manufacturing processes 84 Acid etching Stacks atop roof 14

17 Manufacturing processes Problems Mechanical Cripples are buckles in upper troughs of panels 87 Mechanically caused dents in panels 88 Abrasions in panel due to seamer 89 Scratches in panel 90 15

18 Cuts precipitated corrosion and peeled paint Damage assessment Hail Functional damage 1. Reduction of water shedding capability 2. Reduction in expected long term service life 93 Functional hail caused damage to metal roofing Rupturing the metal Disengaging a lap element Disengaging a fastener Disrupting the protective surfacing (if present) 94 Steel panels Aluminum panels > 2 1/2 (64 mm) > 1 1/2 (38 mm) Hard hailstones, perpendicular impacts, and materials in relatively good or mid life conditions 95 Thresholds for functional hail caused damage to metal roofing Importantly Dents in metal are not functional damage Hail caused dents do not appreciably thin the metal Factory applied coatings are not debonded or broken by hailstone impacts 96 16

19 Rupturing the metal 97 Rupturing the metal Corroded thin panel broken by hail 98 Inside out corrosion (from the building interior) Disengaging a lap element 99 Disengaging a lap element 100 Obvious gap in roofing Gap in seaming tape within lap seam Disengaging a fastener 101 What size hail dented this painted steel panel roof?

20 Stone-coated Steel Panels Class 4 Impact Rated 103 Hail-caused dents stone-coated steel panels 104 Stone coated Steel 105 Hail-caused dents stone-coated aluminum panels- 106 Close view of dent Note that dents did not align with peeled surface coating Overview Granules missing where dented by hail Factory coatings are tough 107 Factory coatings are tough 108 Analysis of material within dents described as "dirt" 18

21 Disruption of Protective Coating 109 Hail caused spatter marks on galvanized steel panels 110 Hail caused fractures in field applied paint on terne coated steel. Hail caused spatter on Galvalume coated stell panels Damage assessment Wind Functional wind caused damage to metal roofing 113 Where to look for wind caused damage 114 Direct wind caused damage Tearing panels from roof slopes Disengaging a lap element Disengaging a fastener Indirect wind caused damage Rupturing the metal Disrupting the protective surfacing (if present) Look high since wind speeds increase with height Look where wind is deflected away from the structure since these are areas of greatest negative pressures (uplifts) Greatest negative pressures (uplifts) are generated at windward eaves and corners, and leeward sides of ridges 19

22 Painted steel architectural panels torn from windward slopes 115 Panels could be lifted by hand with little effort, note nail at finger 116 Only one small nail secured clip 117 Painted steel architectural panels failed, note screws were too small 118 Specified Installed Painted steel structural panels torn away along windward eave 119 Painted steel structural panels torn away and steel purlins buckled from wind uplift

23 Painted steel structural panels torn away at failed overhead doors 121 Painted steel structural panels failed, note only one screw per clip 122 Galvalume steel structural panels uplifted and standing seam disengaged 123 Structural panels unfolded from clip 124 Underside of deformed panels Wind speed increases with height and greatest uplifts occur at windward edges and corners 125 Indirect wind caused damage (impacts by wind borne debris)

24 127 Repair vreplacement Repair methods Assess hail or wind caused damage Identify damaged panels Cost repair, cost replacement Make economic choice The complexity of many repairs will require bids by contractors Most systems can be repaired Repairing a hole or tear in a metal panel 129 Repair structural panel Metal Roofs: Repair Structural steel panel re cover (overlay) Temporary patch Permanent repair 22

25 133 Questions? Thank you!