Trailer parks and tornadoes
November 7, 2005 9:57 AM   Subscribe

In light of the recent events in Evansville, IN...I once heard that a trailer park is more likely to get hit by a tornado than a regular residential area? Is that true?

If so, why? Is it more accurate to say that there is generally more damage done to trailer parks (because of they way they are constructed) and that more people are injured?
posted by elquien to Science & Nature (14 answers total)
A mobile home is more likely to be damaged in high winds than a permanent house (assuming it is well built with wood framing and siding, etc). Compared to most standard houses, a mobile home is relatively flimsy in construction, and as a result, can't take much before being damaged.

That's why a tornado rips through a town and you only hear about the mobile homes having problems -- the other homes sustained no damage but got the same winds and rains.
posted by mathowie at 10:06 AM on November 7, 2005

Also mobile home parks are fairly high density arrangements. A lot that holds one house will hold 4-8 trailers. A tornado that takes out a single house in your typical suburb will destroy 4-6 trailers in a trailer park making for "better" TV news.
posted by Mitheral at 10:13 AM on November 7, 2005

Mathowie is correct, more specifically there exists ASCE 7-98 standards which Florida and many midwestern areas must abide by. These are strict construction codes that involve calculations from the length of a nail in a roofing tile to door frame construction. They deal with wind gusts primarily.

Trailers can be bought and moved anywhere and to my knowledge avoid most if not all building codes. Keep in mind that trailer parks are built on large expaneses of empty land. While tornados can go up mountains, over water, etc. many of those in tornado alley will tell you that tornados are generally fragile. I've seen tornados break up over bodies of water or small hills many times. Trailer parks are built away from any type of the aforementioned scenery that can be deemed desirable.
posted by geoff. at 10:20 AM on November 7, 2005

An addition to Matt's entry is that trailers are also lightweight and usually sit raised a bit from the ground. Not a really good configuration when dealing with 200 mile an hour winds.
posted by Pollomacho at 10:24 AM on November 7, 2005

I live smack in the middle of the bottom stretch of Tornado alley, and I can tell you -- regardless of building codes -- a trailer is absolutely unsafe during a tornado. I'm not sure about liklihood being increased for hitting trailer parks, unless it is a matter of them being all relatively the same height and layout pattern, allowing wind to pass over it more easily than say, the jaggedy "surface" of a foundation-house neighborhood that has irregular streets and different sized, pointy roofs -- but I'm just guessing. You can buy tie-downs and such for trailers to be more secure during your regular high winds, but I would not trust it at all during a tornado -- might as well just stand outside with a hang glider.
posted by vanoakenfold at 10:29 AM on November 7, 2005

a few years ago, i was living in a trailer park and we got a late october thunderstorm with 100 mph straight line winds ... in the rest of town there were downed trees and limbs, some broken power lines, but not a great deal of damage to buildings and houses ... in the trailer park, very few trailers managed to keep their skirting, which flew off piece by piece to where ever ... some trailers got knocked right off their foundations ... one got squashed by a tree ... a couple lost pieces of their roofs ... there were pieces of skirting littered all over the place including a couple way up in trees and many trailers had their siding peeled back or missing in spots

this was NOT a tornado ... just a strong wind ... watching my empty garbage container spin around between my trailer and the one next to it and feeling the whole house shake and the roof thundering with torrential rain was not a reassuring experience

the park was a mess for weeks ... i hate to think what a tornado would have done
posted by pyramid termite at 10:37 AM on November 7, 2005

I would assume that as trailer homes are more flimsy there would be a wider area of hurricane which would cause damage to a trailer home. There by increasing the likelihood of trailer parks getting damaged during a hurricane.

Either that or God hates poor people.
posted by alexst at 11:06 AM on November 7, 2005

Another reason for trailer homes to pop up as the victims of tornadoes, is that trailer parks are often situated on flat plain-like areas. If you have a valley, more often than not, the trailer park will be situated in its flattest part. Tornadoes also enjoy these same geographical areas.

A + B = Rut Roh.
posted by Atreides at 12:27 PM on November 7, 2005

I don't know about anywhere else, but back in Tulsa, there was a period of time when it seemed like just about every tornado would actually change its path on approach to the city in order to accomodate the position of the trailer parks. Thinking about it later, I realized that it might have been just were the trailer parks are located in the city -- cheap land adjacent to or right near the Arkansaw river. Because of this, you have two contributing factors: 1) the river was on the west side of town and almost every storm (especially tornado producing ones) moves in from the west and 2) the river acted as a barrier against the tornadoes (storms/tornadoes that would tear up towns to the west would effect much less to little damage on Tulsa) so that if a tornado did hit the Tulsa area, the position of the trailer parks ensured that they were set receive a fully powered storm.
posted by The Bishop of Turkey at 12:36 PM on November 7, 2005

I work with meteorologists, and it's a running joke amongst them that trailer parks attract tornadoes.
posted by scruss at 12:46 PM on November 7, 2005

oh sweet Jesus... Arkansas river. With an 's'. I guess that is what we Oklahomans get for saying it wrong.
posted by The Bishop of Turkey at 3:12 PM on November 7, 2005

geoff. - you are somewhat correct in that mobile homes are not governed by ASCE 7 loading standards. But there are 2 other important points:

1) ASCE 7 does not deal explicitly with tornadic winds (although the weaker categories of tornados overlap with hurricane force winds). Generally speaking, buildings are not explicitly designed to withstand tornados because it's just not practical (this includes not just single family residences, but all types of buildings). The buildings that are built to withstand tornados are generally some sort of mission-critical facility, like, say, a data center for one of the credit reporting agencies. This would literally be built as a concrete bunker mostly buried in the ground.

2) In most parts of the country, wind loading is not taken very seriously for one and two family residential design. ASCE 7 wind loads will not apply or be used when designing such a residence (if the residence is even "designed" by an engineer, which is unlikely.) Parts of hurricane country are exceptions, particularly post-Andrew in Florida.

But in most parts of the country, an engineer would not be required in order to design or build most houses - the contractor/builder can follow prescriptive standards laid out in a code like the International Residential Code (IRC.) These types of standards essentially say, this is the way builders have been building wood-framed houses for years, and we've generally been OK, so why engineer them? You may be surprised to learn that even in parts of an earthquake prone state like California, this attitude is not changing very quickly.

Anyway...One of the main problems with trailers is that they are not often positively connected to a foundation (i.e. bolted down to a concrete footing or slab.) Now it is true that many regular houses are not either, particularly older houses (mine included, circa 1912). But trailers are much lighter than normal houses (as Pollomacho said), and so are more likely to be picked up and moved by heavy winds.

Sorry for the ramble...
posted by pitchblende at 5:37 PM on November 7, 2005

I was thinking it could be the history of the areas.
Like noone wanted to build houses/buildings in that area because of all the tornadoes, so that made the land cheap enough for someone to start a trailer park there.
posted by Iax at 12:38 AM on November 8, 2005

How To Tornado-Proof Your Mobile Home Slate, 11-8-05; you 'spose they read Ask.Me for ideas?
posted by theora55 at 7:17 PM on November 8, 2005

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