Building houses and tornado/high wind proofing (Tim Marshall - others?)

[beaudodson]

I know that Tim Marshall and some others have been complaining about new home construction. Do they have some tips on how to make houses a bit more wind proof? If I remember correctly he was saying something about new housing lacking hurricane straps? Other? What about adding a bit more strength to one of the closets in a house - to be used for shelter?

Are there some sites that have some recommendations on this subject? One of my companies is going to be building four new houses. I wanted to give them some suggestions on how to prevent some of the problems that we have seen recently in some of the tornado surveys (like what happened in TN). There is a limit on the house budgets (of course) but there must be some inexpensive ideas that will make the houses better than most.

Thoughts on this?

Thanks

 

[Aaron Kennedy]

If I recall correctly, the two key components are anchor bolts (anchoring the frame of the house to the concrete foundation) and hurricane/tornado straps (straps that anchor the eaves of the roof to the frame). The garage door is also a key component to structural failure. Putting in a reinforced garage door can sometimes save the house.

 

[Walker Ashley]

Lots of information on this subject in this FEMA doc: http://www.fema.gov/rebuild/mat/mat_fema342.shtm

 

[beaudodson]

Couple of suggestions from that one site...

A gable roof can be strengthened by installing additional braces in the trusses and/or at the gable ends. A qualified builder can also install galvanized metal hurricane straps. These help secure the roof to the walls.

Most doors do not have bolts or pins strong enough to withstand storm-force winds. The American Red Cross recommends installing additional doorbolt materials (costing from $10 to $40). Garage doors can be strengthened by installing horizontal bracing in each panel. Bracing kits can often be purchased from garage door manufactures. You may also need to add stronger supports and heavier hinges for your garage doors.


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I remember something that Tim published (or someone that referenced him) and it was talking about a couple of items that people can do. It seems like one of those was the hurricane straps being properly used. I don't recall hearing about the garage door but I see that appears to be one of the big items.



Would be nice to see those underground tornado shelters in the garages. That is one of the things being pushed in this region. Several new companies installing them. Unsure of what they are charging for those.
​

 

[Bill Schintler]

Structure failures - a few observations

A tornado, rated "strong F2" by the NWS, tore through Iowa City, IA on
the evening of April 13. Several of the hardest-hit areas consisted
of a mix of newer (less then 20 years old) frame-type construction
buildings alongside massive, older, substantial structures constructed
of brick and heavy timbers. Much to my surprise, most the newer structures
seemed to perform much better then the old buildings during the
storm. Complete roof failure, where the entire roof
pulled free from the rest of the structure, was common in the older
structures but was almost non-existant in the new buildings.

A key factor in whether or not the wind load breaches the structure
is the performance of the roof/wall interface and its resistance to
upward forces. As most folks know, a roof acts as an inefficient
airfoil in the presence of wind. During a storm, if the roof remains
intact the overall structure will perform much better. About 15
years ago, local building codes began to require the use "hurricane
straps" to strengthen the roof/wall interface and resist upward
pulling forces. These inexpensive (if installed during construction) steel straps wrap around
the truss and wall double top-plate (top structural member of the
wall) and form a much stronger interface then previous method which
utilized only three 8d (8 penny) nails to fasten each truss to the top
plate. Nails, used by themselves, have poor "pull strength". Despite the "flimsier" construction which
characterizes many newer buildings, it was the strength of the roof
interface that no doubt resulted in their good overall performance
during this weather event.

On a side note, one of the more interesting things I observed happened to
an apartment building under construction in the tornado's path. This
is a large structure, four stories tall and with a foot print of
perhaps 150ft X 80ft. It is a (wood) frame structure with OSB
cladding on exterior walls. An exterior brick veneer was about 50%
complete at the time of the storm, while construction of the roof was
complete.

Following the storm, my brief inspection of the exterior revealed no
significant structural failure; save for numerous broken windows,
missing roofing singles, and the collapse of most of the scaffolding. A
few days later, I spoke with a plumber who is working on that job,
and he mentioned that the entire building slid about an inch along
its foundation. Additionally, it "racked" so that it was "out of
true" by several inches. Hundreds of pre-drilled holes, which run
between walls and floors for the purpose of running pipes and
electrical conduit, no longer lined up and had to be re-drilled. I went
back and looked at the building, and sure enough, it had moved about
an inch – brick veneer and all. While standing at a corner and
sighting up along the broad side of the building, it was possible to
see how the top had bowed out by several inches. There's nothing
that could have been done to fix it (short of demolishing it and
starting over, which they didn't do). The building was completed several after the storm and is now occupied.

- bill

 

[beaudodson]

Thanks...that is interesting. I am defin going to make sure that we cover at least the bases that have been mentioned above and from some of that FEMA info.

I know that there have been a lot of problems across the nation over the last few years. There have been a number of lawsuits as well...dealing with this subject.

 

[Marko Korosec]

I am wondering why houses are not builded in the way to defy the extreme weather you're experiencing there. Is it a money, laws, life- standards or any other causes for this or is it just a basic thought like why to build a better building if we get hit by extreme weather so often?

I'd advice you to visit some places in central Europe, especially along the Adriatic coast where we often get strong winds above 100mph, so people adapted their buildings to survive these conditions.

Also sometimes I am not surprised about the damage caused by weak to moderate tornadoes in the States. I am sure tornadoes here would have been rated at least one rank lower if not two compared to the damage which could be done there.

 

[Greg Stumpf]

I'd advice you to visit some places in central Europe, especially along the Adriatic coast where we often get strong winds above 100mph, so people adapted their buildings to survive these conditions.

While visiting eastern Austria for a weather workshop in 2003, a few of us arranged to have a tour of a new home under construction in the small village of Krumbach. This home typified the standard construction, and the cost of the home was in the same ballpark for American standards for the same size in an average market. We were amazed at the quality of the construction. All outer walls and the floor between the first and second floor were poured stell reinformced concrete. The roof trusses were heavy 15 x 40 cm solid wood, anchored to the concrete walls by metal bolts. Did I mention that this was standard construction (we were told)?

The funny thing was that I was asked to give a presentation on the Fujita Scale and wind damage surveys at this workshop. Needless to say, that presentation was quickly amended to "European standards" after we toured this home.

 

[beaudodson]

I am wondering why houses are not builded in the way to defy the extreme weather you're experiencing there. Is it a money, laws, life- standards or any other causes for this or is it just a basic thought like why to build a better building if we get hit by extreme weather so often?

I'd advice you to visit some places in central Europe, especially along the Adriatic coast where we often get strong winds above 100mph, so people adapted their buildings to survive these conditions.

Also sometimes I am not surprised about the damage caused by weak to moderate tornadoes in the States. I am sure tornadoes here would have been rated at least one rank lower if not two compared to the damage which could be done there.

I am sure it is ignorance on the part of builders and money. A lot of the people building houses are cheaper labor and they do what they are told to do. It is the people above them that should know better (or do know better).

 

[Tim Vasquez]

Below is the house that I grew up in in Germany. All of the walls and floors are 4-inch reinforced concrete slab, and all of the windows have retractable storm shutters. It's always mystified me why houses here in the U.S., especially in the Great Plains, aren't built like this... I guess lumber is cheap, and the disinterest in concrete construction makes it impossible for economy of scale (and thus cheap prices) to take hold.

If you've seen those war pictures of Bosnia, Serbia, and even Chechnya, where construction methods are similar, it's obvious these structures can stand up to a ton of abuse.

And of course, we had a freakin basement. In Oklahoma this would be a fortress.

Tim

 

[tom hanlon]

I am wondering why houses are not builded in the way to defy the extreme weather you're experiencing there. Is it a money, laws, life- standards or any other causes for this or is it just a basic thought like why to build a better building if we get hit by extreme weather so often?

I'd advice you to visit some places in central Europe, especially along the Adriatic coast where we often get strong winds above 100mph, so people adapted their buildings to survive these conditions.

Also sometimes I am not surprised about the damage caused by weak to moderate tornadoes in the States. I am sure tornadoes here would have been rated at least one rank lower if not two compared to the damage which could be done there.

I am sure it is ignorance on the part of builders and money. A lot of the people building houses are cheaper labor and they do what they are told to do. It is the people above them that should know better (or do know better).

Tornadoes are rare events that impact very small areas.
I have not seen the stats but what are the chances of one particular building being impacted by a tornado ?

A windy coast is a different situation. Large areas of strong winds.. Those afffect whole regions. A tornado effects a very small area.

I am not defending the lack of hurricane ties..
Remember during Hurricane Andrew (?) the habitat for humanity built homes faired better than the rest of the contractor built homes, because they actually followed the code. A few metal strips or a nylon strap is cheap insurance against a rare event.

The adriatic coast is different. Houses in the middle of kansas do not often experience 100 mph winds. Sure every once in a great while they experience a tornado but it is very rare and a few hundred metres away the winds may peak at less than 60 mph. You are talking about larger areas of strong winds. Tornadoes are not large areas of strong winds.

People are by nature short sighted. we have only just figured out that building in the flood plain , although extremely convenient, is not a good long term solution. And that is the floodplain, given a timespan of a few lifetimes and you can almost guarantee a flood.

I would say that a house on the great plains is likely to see a tornado in the range of 1/1000 years or less. By then most of them will have rotted away before they blow away.

Note that I am guessing at the probability , I just know that a tornado is very limited in its area of effect. The plains are a large place, how many square miles actually suffer F0 or greater winds per year ? Any where I can look this up.


Hail has a broader area of effect. I am sure that the tower folks have some idea on risk of hail damage, and maybe even some good statistics. I always feel like I am getting to tornado alley when I start to see the hail shields above the microwave dishes on towers. Installing a hail shield is not cheap, they do not put them on towers in my neighborhood.

I am sure that the insurance companies have some metric for tornado risk and I bet it is small enough to be meaningless.

Hail and Hurricanes... still small but large enough to be meaningfull given our lifespans and the like.

Richard Dawkins in the "blind watchmaker" has an excellent essay on chance. He is talking about the chance or random events that drive evolution but the discussion is the same. Given enough time all sorts of unlikely things will happen. Given a short enough time span then all sort of events may NOT happen.

Suppose we lived for 1,000 years.. We would NEVER get into a car. Drive a car for a 1,000 years and you would not live to see year 700. Same goes for tornadoes. Put a house anywhere on this planet and it is likely to survive for a 1,000 years with no tornado. We are happy with houses that live as long as we do. And a huge majority houses on the plains will not see a tornado for the next 100 years.

So I guess it depends on how long you want that house to survive. For human terms.. I imagine that tornado risk is insignificant. Now if you want that roof to last 1,000 years, or 10,000 years.. well then you had better start to worry about stuff like tornadoes, earthquakes, metoers.. well maybe not meteors.



--
tom h

 

[Gene Moore]

Tornadoes are rare events that impact very small areas.
I have not seen the stats but what are the chances of one particular building being impacted by a tornado ?
I would say that a house on the great plains is likely to see a tornado in the range of 1/1000 years or less. By then most of them will have rotted away before they blow away.

Note that I am guessing at the probability , I just know that a tornado is very limited in its area of effect. The plains are a large place, how many square miles actually suffer F0 or greater winds per year ? Any where I can look this up.

Richard Dawkins in the "blind watchmaker" has an excellent essay on chance. He is talking about the chance or random events that drive evolution but the discussion is the same. Given enough time all sorts of unlikely things will happen. Given a short enough time span then all sort of events may NOT happen.

Suppose we lived for 1,000 years.. We would NEVER get into a car. Drive a car for a 1,000 years and you would not live to see year 700. Same goes for tornadoes. Put a house anywhere on this planet and it is likely to survive for a 1,000 years with no tornado. We are happy with houses that live as long as we do. And a huge majority houses on the plains will not see a tornado for the next 100 years.
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tom h

[FONT=&quot]I agree with what you just wrote to a point, much of the country doesn't need to worry about taking a hit from a tornado. That said, people in particular areas would be irresponsible to not build with tornado damage in mind. You speak in terms of 100 to 1000 years, but in the time I've been chasing I've seen enough to point out areas that defy these numbers. For instance, the small communities around and especially southwest of Wichita, Kansas have been taking hits since I've been chasing. Some of them have endured so many tornadoes that they build their houses in concrete pits. One such home was completely blown out of a three sided concrete structure built into a hillside. This happened during the Conway Springs KS tornado in 2004. See: http://www.crh.noaa.gov/ict/scripts/viewstory.php?STORY_NUMBER=2004053122
Consider the title of the document, [/FONT]Tornadoes Hit Harper County for the Second Time in Less Than 3 Weeks. Additionally,[FONT=&quot]over a dozen tornadoes occured that evening over a small area, not just one. The fact that homes pictured had "safe rooms" indicate they were ready and had been it this situation before.

Moore, Oklahoma is another city that just gets hammered. Remember they were hit again after the famous 1999 event. In fact, there was a tornado there when I was going to OU in the mid-70's that killed a one or two? people. Perhaps it would be a good Stormtrack topic, name the town where the most tornadoes hit. If we look at the statistics Oklahoma City has remained at the top. Just last season the El Reno tornadoes were on the west edge of the OKC metro area and could bee seen from downtown. What are a few more high risk areas that come to mind.....Bennett CO area, Wichita Falls TX and so on. Recently a new geographic addition would be anywhere in SE South Dakota. Additionally, SE South Dakota has been the location of some of the best photogenic tornadoes. The region missed out last spring, but certainly made up for it in the fall with a big stovepipe tornado.

We are building a new house on Lake Amistad (west of Del Rio). For my risk see Roger Edwards recent paper: Supercells of the Serranías del Burro (Mexico): http://www.spc.noaa.gov/publications...s/delburro.pdf

I've read through all the recent papers and government documents about home construction and honestly find little of value. There are pounds of data on what happens to a house during a tornado, but very little on how to prevent it from coming apart. For instance, in many of the images I saw exterior walls of concrete block construction that were left hollow. That is, stacked blocks with grout to level them. They just fall like dominos, but build that structure correctly, steel rebar and poured concrete in the cells and it gets quite expensive. I think after all I've read that the main problem is "pine," it's a very weak construction material to begin with. But, I can't build a solid concrete house on the Mexico border, it would be hotter than hades at night.

Gene Moore
[/FONT]

 

[Brian Stertz]

Yes certainly agree Gene...there are areas/towns that are more snake-bit than others around the Plains and Deep South. I'll make a list of the multiple tornado strikes on cities, towns, and communities. It will be tons harder to get a comprehensive list of the rural areas without doing a path by path overlay. I'll get this list published in the next week or so.

 

[beaudodson]

Whether the odds are good or not? I don't know. I can tell you that I literally know hundreds of people in this area that have lost roofs or have had damage from tornadoes and high winds. That is the people that I actually KNOW...not know of. So it happens around here a lot. The last few years have been brutal.

 

[tom hanlon]

Whether the odds are good or not? I don't know. I can tell you that I literally know hundreds of people in this area that have lost roofs or have had damage from tornadoes and high winds. That is the people that I actually KNOW...not know of. So it happens around here a lot. The last few years have been brutal.

I would like to see the maps or the sum square miles of damage per year.

To be honest I really do not know what the odds are. I suspect after chasing for a few years and all the busts... Well I suspect that tornadoes are a myth.

My point was just to not forget that tornadoes are localized events.

--
tom