Deck Collapse

[John Raabe]

http://www.southtownstar.com/news/2698932,091110deckcollapse-web.article

Outside decks are subject to weathering and general neglect. When they fail it is usually at the connection to the main building - the failure also usually waits until the deck is fully loaded with people. The accident above could have been much worse if the deck had been higher in the air, over a ravine, etc.

When building an exterior deck you want to make sure you have a solid bolt or lag screw connection between a well built deck and a well anchored header in the main building wall. This connection also must be able to move water through the deck without soaking structural members or corroding the anchoring metal parts. It can be tricky to satisfy all these specific needs at the same time.

You should include a careful designed detail in your project plans if you are considering an elevated deck. Your helpful building inspector may have one that has proven to work well in your climate.

For members of our sister site PlanHelp.com, there is a well researched scaled detail you can paste right into your plans. It's in the Plan Details section of the download library.



Here's the information link on PlanHelp for non-members: http://www.planhelp.com/public/10.cfm

[rocking23nf]

you should watch the holmes on homes episode of the lady with the collasped deck from 2-3 stories up. Contractor used improper lag bolts, quite the show

[John Raabe]

http://www.youtube.com/results?search_query=deck+collapse&aq=0

Quite a few good YouTube videos on the topic.

[davidj]

The Prescriptive Residential Wood Deck Construction Guide at http://www.awc.org/Publications/DCA/DCA6/DCA6-09.pdf has lots of details.  It's based on IRC 2009 and has a bunch of differences from the stuff I've read before, including:

• Updated ledger details so that the flashing protrudes past bolts and hangers
• Horizontal hold downs at ledgers to provide lateral strength
• Horizontal hold downs for "guard posts"

[John Raabe]

Thanks Davidj,

Great resource! This detailed report has clear diagrams and covers lots of special conditions such as bracing for tall posts.

[Don_P]

The Deck Guide and much of the research on deck collapse comes from Dr's Woeste and Loferski at Va Tech. Much of the funding has been out of their pockets. I've taken a class given by them, they showed plenty of failures, some with fatalities, and also showed us their lab and test setups. Being the only carpenter in the group, we busted my nailed assembly. Our state considers DCA6 to be a prescriptive deck guide as do many states. Don't forget the best deck is built as a freestanding deck with posts at the house supporting an inboard beam rather than a bolted on ledger hanging from the house. A cantilevered rim is not sufficient support for a ledger. The ledger may be bolted but the rim is just nailed.

[rwanders]

Too many just blindly lag through the siding, hoping they will hit enough "meat" to hold the load up.  Freestanding is always the best choice when adding a deck to an existing home.

[MushCreek]

I like the idea of these. I read the code acceptance, and they get their rating using 1/2" bolts through the rim joist. I don't think those are going anywhere! Seems like a great way to attach a deck; I intend to use them on my build. http://www.deckbracket.com/