Deck Collapse in North Carolina 6

[Ron]

Another wood structure collapse. This one has clean drop at joist buckets. Hmmmm.....fastening issue perhaps?

News story notes it as a "balcony collapse"; however, it is an elevated deck.

Deck Collapse

A photo is attached as well.

 

[SlideRuleEra]

Ron - I believe you have named the cause - fastener failure. The house is 29 years old (per

http://www.zillow.com)

and ocean front. Looks like a typical Carolina style beach house. Fasteners used in the 1980's would be hot dipped galvanized nails - nominal useful life of say 20 to 25 years with the harsh salt air exposure.

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[TehMightyEngineer]

Not knowing anything it seems a fastening issue just given the clean break with no remaining joist structure.

Maine Professional and Structural Engineer.

http://www.fepc.us

 

[SlideRuleEra]

Preliminary findings reveal the floor joists and fasteners failed to hold the deck together, Emerald Island Town Manager Frank Rush told ABC News today. Results from the investigation could be released as early as Monday, he said.

http://abcnews.go.com/US/inspectors...-north-carolina-beach-house/story?id=32227953

Looks like the floor joists and deck all came down together:

Bay that collapsed before photo:

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[hokie66]

I'm guessing that the joists were sitting on small ledgers which were in turn nailed to the beams. When the nails corroded away or failed in end grain tension, the beam moved laterally to the outside, and the joists just fell off.

 

[SlideRuleEra]

Hokie - Right you are about the ledgers:

Hot dipped galvanized nails in this salt air / spray environment typically corrode at the junction of the wood members. They will "neck down" at this spot to almost nothing as years go by. Emerald Isle is on the lower end of the Outer Banks, the land is an isthmus only a couple of blocks wide, from the Atlantic Ocean to the (salt water) Bogue Sound. That part of North Carolina gets many close calls from hurricanes and other storms - a constant barrage of salt spray from all sides.

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[hokie66]

It seems that we read about at least one of these a year.

 

[dhengr]

Unfortunately, we treat decks (and maybe even balconies, another thread) as if they are a Saturday afternoon, keg of beer with the guys, all owning a hammer and knowing everything, as if they where a simple DIY’er. project. Well... they can fail and hurt people, just like any other structure if not properly designed and maintained. Interior structures need some less maintenance becuase they are protected from the weather. Otherwise, these deck structures need no less attention to design, detail and maintenance than any other structure. We can not keep codifying everything so that just any damn fool can do it, if only he can read the convoluted code and follow it. Building and designing any structure is serious business, and just anyone who owns a hammer and a cordless drill motor may not be qualified to do that work. I don’t have a great deal of sympathy for the know- it-all DIY’er. who builds an insufficiently strong or improperly connected deck, we have determined/allowed that any damn fool should be able to do anything, as long as they pretend to follow the code and pay a fee to the city so they can get a building permit. I think the city should be held more accountable when they supposedly review the plans, collect a fee for doing same, and issue a building permit. I think the old Hannibal rule should apply to these DIY’ers, if you hurt or kill someone, they to join them in their fate. I also think the big box stores should be held more accountable, when they provide some nifty software program which shows the DIY’er. exactly what lumber and hardware the store wants to sell them, and then the fine print says, ‘but we are not responsible for anything.’ I can’t imagine why people don’t shop for heart transplant operations or knee replacements the same way.

 

[hokie66]

Hammurabi, dhengr.

 

[msquared48]

Construction is like raising kids... you just have to be smarter and have more foresight than your opponent.

Mike McCann, PE, SE (WA)

 

[IRstuff]

The photo shows nails still attached to the beam, which suggests that the nails didn't fail, and might suggest that it was the wood that failed, particularly if the wood wasn't properly sealed or maintained.

TTFN
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[podosci]

if this continuous the building codes should be revisited

 

[hokie66]

IRstuff,
I can't really see the nails, but my eyes are not too good. But nails in the end grain of wood are not very effective even when new. With a bit of corrosion, and a bit of splitting of the wood, they are no good. What I am guessing that happened is that the edge beam rotated due to the eccentric loading and perhaps some lateral load from the people, and the joists just dropped off the ledger. To prevent this type rotation, tension ties are required, and the nails were not good enough.

 

[SlideRuleEra]

I believe we will know for sure by Monday. This incident was the lead story on NBC's nationally televised news in the USA this evening.

I'm puzzled why the news media continually calls the structure a "deck". In the Carolina's we call what I see a "screen porch". A screen porch has a roof... a deck does not. An ocean front screen porch roof is of no value protecting the fasteners from corrosion by salt air / spray, but does shelter the lumber somewhat. In the 1980's, in the Carolinas, the stringers and decking would typically be treated (0.25 PCF CCA) southern pine. If so, the lumber should be in reasonably good condition.

From the photos, I would say the original 1986 design and construction were above average for the time and location. Meaningful building codes in NC and SC small towns, like Emerald Isle, are an ongoing 21st century development.

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[MacGruber22]

a bit off topic - I talked to one of my fickle clients (contractor) the other day about the progress of his work re-building the floor framing of a church which had a serious case of the termites. I wanted him to hire us to inspect the work, because I knew it wouldn't be done otherwise. In the midst of that conversation, he had the gall to tell me that he didn't need a building permit because it wasn't residential construction, and that they (the code officials) wouldn't care about the church as much. (!!!!)

Point being: these types of residential structures get build after the initial home construction on such a frequent basis without a permit. Not sure how beefing up prescriptive code will mitigate impromptu decks/porches/balconies without a competent contractor, no permit, and no independent inspection.

Personally, I think the strengthening of criminal statutes in this matter is warranted.


"It is imperative Cunth doesn't get his hands on those codes."

 

[ChiefInspectorJeff]

Here are 2 solutions.
1.Insurance companies employ inspectors.
2.Homeowners hire inspectors who work for an agency that employes Lawyers.
Otherwise the corruption will continue, through government officials coerced to pass illegal thing just to keep their jobs.
I put up with it for 17 years.If you only knew!!

Inspector Jeff

 

[MacGruber22]

I like your number 1 as an addition to a more comprehensive solution, Jeff. I believe that the solution to these collapses need to come via "small" changes from numerous angles. I think we have a tendency to pick one aspect (design, construction, etc.) and throw all of our weight into it.

"It is imperative Cunth doesn't get his hands on those codes."

 

[dhengr]

Hokie:
Thanks, I knew it was one of them thar guys. I’m not quite sure were that came from, what with all the elephants, Alps mountains and all that stuff. I’ll wake up some time later today. I’m still suffering from shell shock from the fireworks yesterday. It sounds like you got it right on the rusted nails.

 

[Brad805]

That deck does not look like it has had an ounce of maintenance in years.

 

[IRstuff]

This appears to the the best picture I've seen:

https://lintvksnw.files.wordpress.com/2015/07/58ff777f9d45483692c24f4be3b11610_8.jpg

Nails appear on the right side beam, but not the left.

TTFN
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