Deck Collapse in North Carolina
Deck Collapse in North Carolina
(OP)
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.
News story notes it as a "balcony collapse"; however, it is an elevated deck.
Deck Collapse
A photo is attached as well.






RE: Deck Collapse in North Carolina
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RE: Deck Collapse in North Carolina
Maine Professional and Structural Engineer. www.fepc.us
RE: Deck Collapse in North Carolina
Looks like the floor joists and deck all came down together:
Bay that collapsed before photo:
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RE: Deck Collapse in North Carolina
RE: Deck Collapse in North Carolina
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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RE: Deck Collapse in North Carolina
RE: Deck Collapse in North Carolina
RE: Deck Collapse in North Carolina
RE: Deck Collapse in North Carolina
Mike McCann, PE, SE (WA)
RE: Deck Collapse in North Carolina
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RE: Deck Collapse in North Carolina
RE: Deck Collapse in North Carolina
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.
RE: Deck Collapse in North Carolina
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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RE: Deck Collapse in North Carolina
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."
RE: Deck Collapse in North Carolina
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
RE: Deck Collapse in North Carolina
"It is imperative Cunth doesn't get his hands on those codes."
RE: Deck Collapse in North Carolina
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.
RE: Deck Collapse in North Carolina
RE: Deck Collapse in North Carolina
TTFN
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RE: Deck Collapse in North Carolina
http://www.foxnews.com/us/2015/07/06/deteriorating...
RE: Deck Collapse in North Carolina
Mike McCann, PE, SE (WA)
RE: Deck Collapse in North Carolina
Richard L. Flower, P. E., LEED Green Associate
Senior Structural Engineer
Complere Engineering Group, Inc.
RE: Deck Collapse in North Carolina
With nails sticking out up above - it seems like the bond between the nail and joist was such that many simply pulled out of the end grain.
This may not be the initial cause of the collapse - perhaps something gave way in shear and that started a domino effect as the deck joists pulled away from the supporting beam.
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RE: Deck Collapse in North Carolina
Richard L. Flower, P. E., LEED Green Associate
Senior Structural Engineer
Complere Engineering Group, Inc.
RE: Deck Collapse in North Carolina
Years ago I made that very comment to a representative of Simpson Strong-tie. He, being more directly involved in that specific corner of our industry, replied, "More like every week." And I didn't get any sense that he was joking or using hyperbole.
RE: Deck Collapse in North Carolina
The edge beam rolled when loaded, and there were no nails left to resist.
RE: Deck Collapse in North Carolina
I propose all the corroded nail on the left side sheared (the nails into the ends of the joist and the nails holding the ledger in place).
As the left side of the floor descended the joists rotated downward... pulling away from nails remaining in place on the right.
This explains why no full length nails are visible on the left side, yet the right ledger and full length nails are visible on the right.
The photo JAE furnished, showing nail holes, must be of the right end of the joists.
Here is the enlargement of the left side:
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RE: Deck Collapse in North Carolina
How many times have we all wanted to say to a client, please put down the hammer and tool belt?
RE: Deck Collapse in North Carolina
Richard L. Flower, P. E., LEED Green Associate
Senior Structural Engineer
Complere Engineering Group, Inc.
RE: Deck Collapse in North Carolina
TTFN
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RE: Deck Collapse in North Carolina
Yes, I agree. That stands to reason, as the exterior one is the most susceptible to the weather.
IRstuff,
No, joist hangers are nailed, so the same corrosion problems exist.
rlflower,
The outer islands of North Carolina, as well as all barrier islands, are an extreme marine environment. Simpson's satisfaction would not satisy me.
RE: Deck Collapse in North Carolina
Richard L. Flower, P. E., LEED Green Associate
Senior Structural Engineer
Complere Engineering Group, Inc.
RE: Deck Collapse in North Carolina
RE: Deck Collapse in North Carolina
Mike McCann, PE, SE (WA)
RE: Deck Collapse in North Carolina
Looks like the left ledger dropped and allowed rotation that pulled the right side of the joists out from the beam.
The ledgers were installed on the bottom of a double beam, with all the fasteners in tension (however few of them there were). Ledger fasteners should be in shear, not tension. Even if the fasteners did not corrode, it would be easier to overload the pullout in this orientation.
RE: Deck Collapse in North Carolina
RE: Deck Collapse in North Carolina
Double 2 x 10 beams, approximately 10' long.
2 x 8 floor joists @ 16" O.C, each approximately 12' long.
2 x 2 ledger with 3 nails under each joist (probably 16d or 20c common). Nails loaded in shear.
Remains of toenails from joists into beams (probably 12d or 16d common).
5/4 x 6 deck boards.
All lumber color and condition (29 years old) consistent with CCA-C treatment.
All nails hot dip galvanized.
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RE: Deck Collapse in North Carolina
I think you'd have to be nuts to construct it as I described above, but considering the amount of bad construction I've investigated over the last 35 years, not much surprises me anymore.
Looking at the band below the sliding glass doors, the left side looks like maybe a 2x12 and the right side narrower and is pieced with a 2x2. Why? That member picks up essentially no load.
RE: Deck Collapse in North Carolina
RE: Deck Collapse in North Carolina
RE: Deck Collapse in North Carolina
1. Where is the left rim in the first picture? Had it already been removed or lost?
2. I wondering if the lower corner was hit looking at the vertical misalignment of the top to bottom columns. May have been constructed that way though.
3. If the section just dropped vertically, why is the handrail damaged?
Something else happened.
Mike McCann, PE, SE (WA)
RE: Deck Collapse in North Carolina
RE: Deck Collapse in North Carolina
Seems ridiculous that posting the deck capacity in terms of the number of people would become necessary to shift liability from the designer, but maybe it has come to that with idiots presently in this system of things. It most certainly not have prevented this accident, but certainly have distributed the liability.
Mike McCann, PE, SE (WA)
RE: Deck Collapse in North Carolina
from the County Building Codes Administrator that has his investigation results:
The complete report is attached below (.pdf, 19 pages, 8.8 MB)
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RE: Deck Collapse in North Carolina
The Building Codes Administrator reported that the nails appeared to be galvanized. Would this typically indicate hot dipped galvanized, or could it mean electro-galvanized nails?
RE: Deck Collapse in North Carolina
HDG nails are widely used there, because of corrosion, and more available than inland.
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RE: Deck Collapse in North Carolina
Honestly, I don't know how you engineer this. I think this is like the folks that have a water heater in their attic. You replace it every 10 years whether you need to or not, because you sure don't want to wait for it to break. Problem is that most all of the houses in the worst environments in these areas are rental properties where the owner wants to do as little as possible in maintenance, and I can't blame them for that.
RE: Deck Collapse in North Carolina
RE: Deck Collapse in North Carolina
Comments:
Looking at the pictures I don't see how anyone can determine what was galv was used (if any). In the 1980s Hot dip Galv was not always used on coastal decks.
Loading 24-26 people on the 1/3 western corner of a 8'6x10' deck overloads the structure (I believe the SBC used 40 PSF in the 1980s)
RE: Deck Collapse in North Carolina
RE: Deck Collapse in North Carolina
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RE: Deck Collapse in North Carolina
IR, 316 is very good in marine environment, chart has mistakes
RE: Deck Collapse in North Carolina
boo1, I know that stainless fasteners are relatively new. I was just making a suggestion to the poster before me.