Deck Failure Stats 2

[phamENG]

Anybody have any good sources for deck failure statistics? I'm meeting with a developer I've been working with for the past year later this week along with his "deck guy" who has been causing nothing but problems - of course he has accused me of picking on him and I'm the one causing the problems. These things look like not quite passable DIY jobs - guardrails connected with a few screws (or toe nails!), stair connections questionable at best, no lateral support, etc.

I'm going to have the code and can point to all the things that are wrong, but I'm anticipating a lot of push back and the typical "we've always done it this way" and "the city inspectors don't call us out on this" so I want to have something that at least the developer will understand. My gut feel is that the vast majority of structural failure related injuries occur on decks and balconies, but I don't have any coherent stats on it.

Thanks.

 

[EngineeringEric]

I don't know of any, but you may want to reach out to VT Joseph R. Loferski. He has many publications and is very involved with wood decks (and their failures!). He'd be worth an email/phone call and maybe even browse his publications for some stats.

I've worked with in the past on some FRT failures and we've had him/his lab test members for us for capacity.

 

[bones206]

Companies like Simpson probably have a vested interest in knowing these kinds of stats. They even have some Youtube videos showing deck collapses.

 

[ATSE]

Non-engineering suggestion. I would not even entertain the "we've always done it this way" which is equivalent to "I haven't worn a seat belt in 20 years and never been hurt" argument.
When faced with this common attitude by marginal contractors, my comment back to the owner is: I design and build 100 year structures. Not 10 year structures. And the cost difference between a 100-year structure and 10-year structure is not 10x, but more like 25%.
You might need to start focusing on different clients as well.
I completely agree with you about gut feel - decks and balconies have got to be the most common structural components to fail (precast assemblies not far behind).

 

[ATSE]

 

[SlideRuleEra]

Many DIY residential decks should take a 40 PSF uniform live load. The problem comes when a group of people stand close together for a photo (~75 to 100 PSF).

Ask the "deck guy" if he wants to be under one of his decks while a group of volunteers doing a DIY load test.

http://www.SlideRuleEra.net

 

[StrucDesignPE]

These things look like not quite passable DIY jobs - guardrails connected with a few screws (or toe nails!), stair connections questionable at best, no lateral support, etc.

I'm going to have the code and can point to all the things that are wrong, but I'm anticipating a lot of push back and the typical "we've always done it this way" and "the city inspectors don't call us out on this" so I want to have something that at least the developer will understand. My gut feel is that the vast majority of structural failure related injuries occur on decks and balconies, but I don't have any coherent stats on it.

I think I would strongly emphasize this and point out that the building code is a minimum standard. If a deck on one the developer's houses falls and causes property damage or personal injury, then one of the deciding factors in a lawsuit is going to be if the deck was built to the building code's minimum standards. City inspectors have no liability in such matters of work being approved or not. If there is one thing developers understand, its money.

 

[JoelTXCive]

I'll attach my deck articles. They might have some photos you can use in a discussion.

See attached....

Diagram on how loading is usually not uniform on a deck because everyone congregates at perimeter.

 

[JoelTXCive]

Why Decks Fall Down Article... Some good images...

Fine Homebuilding 2015

 

[JoelTXCive]

Differences between Commercial Decks and Residential Decks..

Deck Builder Magazine 2009

 

[phamENG]

Thanks, everyone. Fortunately the developer is mostly on my side. The guys in the office just want the cheapest guy and fewer complaints from the field, but the supers see what I'm seeing and want it dealt with. The back office guys are the ones I'll have to convince with stats on failures and injuries, because they're closest to the accountants and lawyers.

Trust me, I never entertain the "we've always done it this way" argument as justification. I'll listen to it, and then either prove that it meets code or prove that it doesn't. If it doesn't meet code, then that just means you've been doing it wrong forever. Too bad.

Joel - nice articles. Thanks.

 

[StrucDesignPE]

Here is an article I dug out of my archives. It references common code violations and failures and it local to your area.

https://files.engineering.com/getfi...ile=Common_Code_Violations_tcm122-1378910.pdf

 

[drawoh]

ATSE,

Nice pictures. Would I be correct in assuming that some of those failures were fatal?

--
JHG

 

[XR250]

I usually tell them my insurance won't cover me if it is not to code. Probably not true, but it sounds impressive nonetheless.

 

[KootK]

I get some mileage out of offering up load testing. Something like:

Sure, if you're confident in your build, go for it. The we'll load test it to a multiple of the code loads. Of course, you'll pay for the testing and if it falls apart, you'll pay to rebuild it differently.

Once I ask folks to share fairly in the risk that they expect me to assume, I find that they settle down some. A former mentor of mine once told me that, whether it comes to architects or contractors, the answer is never "no". Rather, the answer is "yes" but, possibly, at ridiculous cost and unappealing stake in the liability.

For what it's worth, I doubt there's a code compliant deck or handrail in all of Alberta.

 

[NorthCivil]

@ ATSE

That collection of photos you have - brings back a lot of memories, a lot of those collapses have been discussed on this website, some of those collapses resulted in deaths. The photo showing the seriously rotted out failed joists resulted in 7-8 deaths if i recall correctly, it was university students at a party in the SF bay area i believe.

 

[NorthCivil]

In my old deck days, i always designed decks for 100PSF.

Whenever I hear "we've always done it this way"

I always counter with

"Sorry, cant approve that, its company policy"

People are a lot less prone to arguing with policy than the recommendation of a sole engineer. never mind the company is a one man band

 

[Settingsun]

This presentation has some US stats (collected by Dr Loferski mentioned earlier) and also some Australian cases/numbers.

https://files.engineering.com/getfi...liably-durable-timber-structures-tq-10-17.pdf

 

[phamENG]

steveh49 - perfect. That has some real numbers I can use.

KootK - nice idea. I'll keep it in my back pocket, but I'm reluctant to hint that there may be a way to say it's okay as is - somebody will latch onto that and say if there's a chance we might as well assume it'll work since the contractor says he's always done it that way and, after all, we have a schedule to keep. And since the city is back to work doing inspections, they'll see my adherence to the code and good engineering sense as more of a hindrance than my flexible and reliable scheduling. (I've been doing inspections for them since the municipalities stopped sending inspectors out.)

 

[DrZoidberWoop]

Pertinent quote following a famous failed assassination attempt:

Jane Spencer:
How could you do something so vicious?

Vincent Ludwig:
It was easy my dear. You forget I spent two years as a building contractor.