Chances of a tree falling on a house - logically

toronado3800 Zone 6 StLouis(6)December 12, 2011

Another post got me thinking about this.

My theory is a residential shade tree will shed about six large branches of the type which will put a hole in your roof or ruin your car / kill you during its life.

(This is an oak dropping a branch btw)

The average life expectancy of residential trees I could not find. If left to decline on their own I bet a good number of sycamores, cottonwoods and even silver maples would hit 100 years if they survive the first ten after transplant. Perhaps longer for other species. The big live trees I have removed around 50 years of age were very much alive, just threatening to their environment. So I'll pick 75 for a decent life expectancy. Anything more and it is a noteworthy old tree. Anything less and you are annoyed it did not outlive you.

(White ash, so strong they make baseball bats out of it)

So if a tree is to lose 6 large branches during a 75 year life math says that is one ever 12.5 years or an 8% chance of it happening in any year.

Of course the first twenty years of the tree's life it probably will not lose any meaningful branches so that becomes 6 over 50 years. 12% in any one year. Yup, a 12% chance of that branch falling.

Now we need to do a couple things. One is figure out how much of it is overhanging your home / car / shed. The old trees near my home were planted too close. They seem to have had up to 1/3 their canopy over my house or where I parked my Toronado, El Camino, Mustang or now the MarkVIII.

So of that 12% only a third of it REALLY matters. So a 4% chance of catastrophe in any year over the last 50 years of the tree's life.

That would leave 1 of every 25 homes damaged by trees in any year. Thank goodness we usually get warnings and have our trees removed as the odds change with their increasing age before our shade trees remove us.

(This warning sign was gone two days later)

(Not the same tree but nice split in this one. You could see a little seam on the outside where that water was getting in)

The odds change greatly as a tree ages. Late in the lives of five silver maples on my street there were branches falling all the time. Perhaps years 25 to 40 you have a 2% change of limb drop. 41 to 60 that 4% and 8% from 61 to 75. Who knows the exact years. With old trees they need inspected!

In closing I would like to say it is the homeowner's responsibility to hire someone or pay enough attention to their trees to keep the odds from catching up with you and killing your kids or car. I was not that observant in the past but have learned.

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ken_adrian Adrian MI cold Z5

too many peeps simply dont think about it.. and fall for the tree-hugger mentality of not killing something that threatens them .. their progeny.. their property ... or their neighbors ...

its a tree .. kill it if it has the potential to kill you ... where in that equation is respecting its life ???? if you can abort a baby because it will negatively effect your lifestyle .. why not a tree???? [most children will not kill you in your sleep]

and you find out its potential.. by paying a professional tree person for an onsite inspection .. we can NOT really guess on the web, with a few pix .. and the local guy with a chainsaw is not necessarily a professional trained in tree health ...


Here is a link that might be useful: do you still have it????? which one

    Bookmark   December 12, 2011 at 9:16AM
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alan haigh

I'd be much more interested in actual statistics from insurance companies of real damage. What you've posted is not a reliable way of compiling statistics but a good way to start a discussion, IMO.

I live in an area where giant old trees hang over most peoples homes and I don't think your deductions hold water at all. Most often fallen branches cause no structural damage to homes and usually when I read of human injury from branches or falling trees it occurs while the victim is driving in a storm.

    Bookmark   December 12, 2011 at 9:58AM
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ken_adrian Adrian MI cold Z5

hey harvest..

it might not be about the actuality ..

as much as the fear ...

e.g. ... the odds of getting hit by lightening are right up there with winning the lotto ..

though i do buy lotto tickets now and then .. [only when its over 100 million.. because its not worth a buck spent on anything less .. lol]

i rarely grab the golf clubs and go out in a thunderstorm ...


    Bookmark   December 12, 2011 at 4:53PM
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Ken you are really missing out! Some of the most exciting times of my life have happened during pop up thunderstorms on a golf course!!!

    Bookmark   December 12, 2011 at 5:03PM
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ken_adrian Adrian MI cold Z5

wait.. i just reread the title ...

whats logic have to do with unbridled fear .. lol ..

hey jon.. let me guess.. to get away from the lightening.. you went under the closest tree .. and it tried to slaughter you in your golf dreams.. lol


    Bookmark   December 12, 2011 at 7:26PM
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toronado3800 Zone 6 StLouis(6)

This Toro Ken, the one with the 3800!

And the fancy factory touch screen dash which actually stayed working for 270k miles.

    Bookmark   December 12, 2011 at 11:57PM
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whaas_5a(5A SE WI)

At the end of the day your more likely to die of another cause before you OR your house is struck.

I came across stats at one point and they were quite incomplete because the numbers are so mindboggling small.

    Bookmark   December 14, 2011 at 1:41PM
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depends...know a guy named Murphy?

    Bookmark   December 14, 2011 at 2:45PM
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whaas_5a(5A SE WI)

Yeah, he is pretty paranoid.

    Bookmark   December 14, 2011 at 5:59PM
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He is also forgetting that only one of those limbs on that tree are going to fall in the direction of the house.

    Bookmark   December 14, 2011 at 8:17PM
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alan haigh

You guys truly crack me up. I tried getting some comic relief on the tube tonite- failed there, but ended up finding it here. Thank you.

I have to admit that I'm too afraid to hang out and continue working in thunder storms although I've no idea what the actual odds are of being Colonel Sandered. Yet I feel no fear when I'm 40 feet up a 150 year old apple tree, ropeless with rot running all through it.

    Bookmark   December 14, 2011 at 8:58PM
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treebarb Z5 Denver

On Tuesday, a 34 year old tree trimmer in Fort Collins was 50 feet up cutting when an upper branch gave way, hitting him in the head and killing him. He hung there for hours because the ladder truck couldn't get close enough to bring him down and they had to wait for a cherry picker to get there. It's dangerous work and I think they earn their money!


    Bookmark   December 15, 2011 at 8:27AM
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botann(z8 SEof Seattle)

I lost a good friend last year that was working for a tree trimming company. The tree had been limbed and the climber was 'chunking' out the trunk in 4 ft. sections. That's what hit him. Some of his ashes are in my garden.
Here in the Pacific Northwest a lot of houses have trees within striking distance. Very few people are killed in their house by a falling tree. I'm all for removing obvious danger trees though. The trick is recognizing them. Some are more likely to blow over, while others are more likely to drop limbs. There are a lot of other factors, but a good education in trees goes a long ways when it comes to safety.

    Bookmark   December 15, 2011 at 8:56AM
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toronado3800 Zone 6 StLouis(6)

Still no stats! And both my mother and sister work for different insurance companies.

I have seenperhaps a dozen trees on houses over the last decade personally. After every storm over the summer the news folks have a couple so I know it happens. So 1,000,000 ppl in the st louis metro area... lets say a doze times a year the news folks have pictures of trees on houses....i need to know how many houses....that should be available.

But still that discounts folks like me who have spent 2k over the course of a decade renting equipment to cut down trees or paying ppl to remove them.

    Bookmark   December 15, 2011 at 10:44AM
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There are 307,006,550 people in the US. In the period between 1995 and 2007 there were 407 tree related injuries.

Based on these numbers from the website below, there is about one death per million every 10 years.

I tried to find similar data for injuries, but after finding thousands of lawyers advertising that they would represent you if you were injured by falling tree limbs I gave up.

However as I remember from the safety classes before I retired for every death there are 10 accidents, so based on this questionable statistic, About one person per year is injured by a tree accidentally falling on him. This does not include the Hey-Bubba-watch-this accidents with a chain saw and trees.

    Bookmark   December 15, 2011 at 12:09PM
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karinl(BC Z8)

It seems to me that the relevant statistic is not how many people out of the whole population are hit by trees, but how many people out of those who live under large trees are actually harmed by them. It doesn't matter how many people there are in total if most of them do not live under trees.

When I lived in the lee of a huge conifer with a dense (sail-like) canopy, my chances of having my family crushed were higher than those of the average population simply by virtue of the presence of the tree. No tree now, now zero risk.

Karin L

    Bookmark   December 15, 2011 at 1:38PM
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brandon7 TN_zone(7)

"In the period between 1995 and 2007 there were 407 tree related injuries."

Knuttle, I think you misread some of the data. According to your source, it's 407 deaths (not injuries) caused by (and reported as caused by) falling trees in storms during that period. That equates to around 34 people per year in this country dying from that particular set of circumstances.

On top of this, and on top of what Karin points out, think of all the people who's lives (homes, property, etc) are ruined every year by unsound trees crushing their goodies. Leaving dangerous trees hanging over your house is somewhat like standing in the middle of traffic...not all that smart.

    Bookmark   December 15, 2011 at 8:25PM
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toronado3800 Zone 6 StLouis(6)

So the tree care industry has about 4,000 injuries and or deaths per year?

Doesnt aound that crazy. A fortune 500 company I used to work for probably logged 1,000 injuries out of only 50,000 employeed bit a good number of us had desk jobs and were not climbing half rotted trees chainsaw in hand.

Amazing how difficult finding these stats is!

Good point that no matter what your odds are, they are way higher if your home is under that branch 24 hours a day for a few decades.

    Bookmark   December 16, 2011 at 1:58AM
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I would still keep the tree unless there is a serious defect.

You can put new trees in when you cut down that 50year old tree, but you can never truly replace it, as you will be dead by the time the tree reaches any significant size. assuming most of you are in your 40's and by the time the tree is of significant size you will be about 90 and statistically have died

    Bookmark   December 16, 2011 at 8:45AM
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alan haigh

In Oct. the northeast had an Oct. snow in areas that hadn't seen such early snowfall in decades at least. It was like a war zone with trees splitting in half (hate those co-dominant leaders) and huge branches just exploding out of ancient oak trees still in nearly full leaf- also tulips (which are our largest forest tree) and anything else that didn't defoliate early because of absurd levels of rain in late summer. Plenty of huge trees were uprooted entirely.

Most of the destruction was to the trees themselves and power lines. I'm sure there were plenty of damaged structures but I haven't seen a single one and I think there was maybe one or 2 deaths in all the states affected by this event.

How do you interpret this relative lack of injury and damage to homes in an event that probably caused 10 years worth of branch and tree breakage in a single night? (OK I pulled that stat out of my hat but it's based on logic, I think).

    Bookmark   December 18, 2011 at 11:38AM
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brandon7 TN_zone(7)

Last year, in Knoxville, we had a bad storm (near tornado strength, but I don't think they ever determined a tornado occurred) and hundreds of homes and businesses were damaged. Going down almost any street, you could find houses with trees dropped onto roofs or cars crushed in driveways. Even a few commercial buildings were heavily damaged by trees. I see tree damage to homes so frequently, that I am very surprised by the trees-in-storms-death statistics sited earlier.

I also see damage, and even deaths, not storm related, surprisingly frequent. For example, just four days ago, here in Knoxville, a lady was crushed to death, as she was driving down the road, by a tree falling. Yes, it was a "freak accident" but certainly not the first one with similar circumstances.

    Bookmark   December 18, 2011 at 12:42PM
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botann(z8 SEof Seattle)

I don't think statistics are going to help much. Too many variables. How would you use the stats if you found some you could live with? What good would be they be?
Each house, it's surroundings, and location, are unique. Statistics, if you find them, would be of very limited value in my opinion.

This western Hemlock has been leaning since before I moved here in 1978. Hasn't fallen yet. It's lodged against a large Acer macrophyllum. The lean has increased the last few years. I sure don't want it anywhere near my house. It's on adjoining property so I can't cut it down. It's been fun to watch though!

    Bookmark   December 19, 2011 at 9:57AM
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