Deck Construction Defects Lead to Deck Collapse Catastrophe
DECK COLLAPSE Case Study - CONTENTS: Deck Collapse Case Demonstrates Improper Residential Deck Construction. List of structural defects leading to deck collapse - what structural connections are critical to porch and deck safety. Photos of improper Deck Joist Hangers & Missing Nails in Joist Hangers - Deck Collapse
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Deck collapse case study documents causes of catastrophic failure:
This article explains critical and poor construction details that led to a catastrophic residential deck collapse. Our page top photograph shows the results of a poorly-constructed deck that collapsed and fell eight feet to the ground, sending three people to the hospital.
Luckily there were no serious injuries but children playing below the deck ran out as it collapse - otherwise they may have been killed.
Owner Ignores Warning to Stay off Unsafe Deck - Leads to Collapse: big party to celebrate moving in overloads deck
During a home inspection we found these unsafe structural details on the deck shown in these photographs
The deck ledger was simply nailed to the building wall over vinyl siding, using common nails; no bolts were used.
Some deck joists were secured to the deck ledger board using steel connectors (not joist hangers) and with roofing nails. Hammering a roofing nail home against a steel joist hanger cracks the thin nail head and risks connection failure. Roofing nails are not structural fasteners.
Other deck joists were "set" into steel joist hangers with no nails whatsoever.
The deck joists were not all nailed to the deck outer girder.
The deck girder was simply tacked to the top of 4"x4" wood posts with no structural connections.
The deck posts went into the ground to an un-known depth. If the deck posts were not buried to an adequate depth that detail added to the risk of deck collapse.
Photos of improper Deck Joist Hangers & Missing Nails in Joist Hangers - Deck Collapse
Our photos above show non-structural angle brackets used to connect deck joists to a bolted ledger at a different property (above right), and a steel joist hanger used to connect a deck joist with no nails whatsoever (above left).
Owner Ignores Warning to Stay off Unsafe Deck - Leads to Collapse
Despite our strong warning to the home buyer to stay off of the deck (witnessed, orally and in writing) and to repair the unsafe deck before use, including a report on whose front page was highlighted a statement that the deck was very dangerous, and that it should be repaired immediately, on moving into the home the new occupants celebrated with a deck party. Sipping a beer, a heavy guest stood at the outer deck railing and idly bumped his weight against the guardrail.
The deck detached from the building and fell to the ground, sending three people to the hospital. Luckily there were no serious injuries but children playing below the deck ran out as it collapse - otherwise they may have been killed.
Photos of Improper Deck Framing Connectors, Insecure Deck Supporting Posts - contributors to deck collapse
Our deck defect photos above are close ups of the collapsed deck. They show a questionable-application deck joist connector with roofing nails instead of structural fasteners (above left), and a deck post that extended only 11" inches into the soil (above right). Other deck posts were only 7" into the ground and none were anchored nor connected to piers.
Photos of inadequate connection of deck ledger to building
Our photo (at left) shows the common nails protruding from the inner face of the deck ledger board. These are the (inadequate) fasteners that pulled out of the house wall as the deck separated from the building and fell to the ground.
Despite multiple inadequate deck construction details and despite the deck having a "CO" issued by a local authority, our opinion was that had the deck ledger been bolted to the building this collapse may have been avoided.
Proper deck flashing at the building is also important to avoid both leaks into the structure and rot or weakening of this critical structural member that secures the deck against falling.
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Mark Morsching, Everflashing, Tel: 800-550-1667, Email: email@example.com. The Everflashing product comes in G-185 and Stainless Steel and is intended for use with treated lumber with copper in it. Everflashing produces a variety of specialty flashing products including flashings for use with decks at deck ledgers and deck perimeters. Quoting [Email 10/30/2010]
I have been a carpenter for more than 26 years, the last 5 in business for myself. I worked in the union and specialized in deck building and hand framing traveling around the country. when I started my own business working on decks I ran into two problems poorly constructed and flashed decks and no account for galvanic reactions. The other problem is the movement (expansion and contraction ) of composite decking. That is how I came up with Everflashing, it allows for expansion and contraction while minimizing water intrusion. It is available in G-185 ( Z-Max ) and Stainless Steel. We also have a perimeter flashing which greatly minimizes water intrusion in between the skirt boards and the outer joists. www.nadra.org is a great source of information and is a non profit organization.
"10-Point Consumer Safety Checklist", North American Deck and Railing Association, NADRA, 888.623.7248, Quoting:
The mission of the North American Deck and Railing Association (NADRA) is to provide a unified source for the professional development, promotion, growth, and sustenance of the Deck and Railing building industry in North America so that members can exceed the expectations of their customers.
"Outdoor Deck and Porch Injury Study", Legacy Services LLC., http://www.buildingonline.com/news/pdfs/Outdoor-Deck-and-Porch-Injury-Study.pdf [No named authors, address] also includes the next 3 citations below.
Consumer Product Safety Commission’s National Electronic Injury Surveillance System, http://www.cpsc.gov/LIBRARY/neiss.html
Kessler, E. and T. Schroeder. (1998). National Electronic Injury Surveillance System (NEISS) Estimated Generalized Relative
Sampling Errors. Washington, DC: U.S. Consumer Product Safety Commission.
National Ornamental & Miscellaneous Metals Association (NOMMA) and Whorton Marketing & Research (WM&R) Climbability,
Research, Analysis, and Communications Planning document, May 31, 2006.
Design of Wood Structures - ASD, Donald E. Breyer, Kenneth Fridley, Kelly Cobeen, David Pollock, McGraw Hill, 2003, ISBN-10: 0071379320, ISBN-13: 978-0071379328
This book is an update of a long-established text dating from at least 1988 (DJF); Quoting: This book is gives a good grasp of seismic design for wood structures. Many of the examples especially near the end are good practice for the California PE Special Seismic Exam design questions. It gives a good grasp of how seismic forces move through a building and how to calculate those forces at various locations.THE CLASSIC TEXT ON WOOD DESIGN UPDATED TO INCLUDE THE LATEST CODES AND DATA. Reflects the most recent provisions of the 2003 International Building Code and 2001 National Design Specification for Wood Construction. Continuing the sterling standard set by earlier editions, this indispensable reference clearly explains the best wood design techniques for the safe handling of gravity and lateral loads. Carefully revised and updated to include the new 2003 International Building Code, ASCE 7-02 Minimum Design Loads for Buildings and Other Structures, the 2001 National Design Specification for Wood Construction, and the most recent Allowable Stress Design.
Diagnosing & Repairing House Structure Problems, Edgar O. Seaquist, McGraw Hill, 1980 ISBN 0-07-056013-7 (obsolete, incomplete, missing most diagnosis steps, but very good reading; out of print but used copies are available at Amazon.com, and reprints are available from some inspection tool suppliers). Ed Seaquist was among the first speakers invited to a series of educational conferences organized by D Friedman for ASHI, the American Society of Home Inspectors, where the topic of inspecting the in-service condition of building structures was first addressed.
Defects and Deterioration in Buildings: A Practical Guide to the Science and Technology of Material Failure, Barry Richardson, Spon Press; 2d Ed (2001), ISBN-10: 041925210X, ISBN-13: 978-0419252108. Quoting: A professional reference designed to assist surveyors, engineers, architects and contractors in diagnosing existing problems and avoiding them in new buildings. Fully revised and updated, this edition, in new clearer format, covers developments in building defects, and problems such as sick building syndrome. Well liked for its mixture of theory and practice the new edition will complement Hinks and Cook's student textbook on defects at the practitioner level.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
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