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Rob
In Deo speramus.
Premium
join:2001-08-25
Kendall, FL
kudos:2
Reviews:
·Comcast

Tornados & House Structure Question..

I've always wondered why homes in States where tornados hit are built of wood and not cinder block like down South (»macsystems.com/May18-2007.jpg) ?

I would think a cinder block home would hold up to a tornado more than a home made of wood?
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beck
Premium,MVM
join:2002-01-29
On The Road
kudos:1
Cinderblock doesn't help. My sister's cinderblock house got wiped in a tornado. Ok, one and a half walls were still there. But really, didn't look much different than other houses.


cdru
Go Colts
Premium,MVM
join:2003-05-14
Fort Wayne, IN
kudos:7

1 recommendation

reply to Rob
said by Rob:

I would think a cinder block home would hold up to a tornado more than a home made of wood?

Doubt it. Cinder blocks work well for compressive strength. Holding things up. Tornados have massive winds, forcing lateral loads. It doesn't take much to knock over a cinder block wall, especially when debris starts impacting it. Add to this that if a tornado is quite close, the wind speeds will often cause windows to break, the roof to lift off, and walls to push out like a balloon.

The only way to build a house to withstand a tornado is to not build it. Or build it underground. Or close but not next to a trailer park. Given the choice between a house and a trailer park, a tornado will always choose the trailer park.


VioletVenom
Lets go Gators
Premium
join:2002-01-02
Gainesville, FL
reply to Rob
With any storm, hurricane or tornado, it all depends upon severity of the storm. Not much is going to stand up to the finger of god, or a Cat 5. Cdru's trailer park theory is sound though!


cowboyro
Premium
join:2000-10-11
Shelton, CT
reply to Rob
Tornado vs cinder block structure:

More images here:»www.srh.noaa.gov/hun/?n=4272011_···b_county
The only thing that will hold against a direct tornado hit is an underground shelter. It's not necessarily the wind, it's also the debris that is like a canon fire against the structure. Do you really think it will hold against a truck that is slammed into it?


marigolds
Gainfully employed, finally
Premium,MVM
join:2002-05-13
Saint Louis, MO
kudos:2
reply to Rob
You can build up buildings that resist up to EF3 with poured concrete walls, not cinder block. Beyond EF3 there is nothing you can do except go underground.


Sennheizer

join:2012-05-14
reply to Rob
We're having a garage built to withstand tornado force winds right now. Like cowboyro pointed out the wood frame structure will be able to survive 250 mph winds but even a small stone or stick at that speed would rip a hole in the building. All things being equal block and wood both hold up the same. Wood is easier and cheaper to deal with so it wins most of the time.


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom

2 edits
reply to marigolds
said by marigolds:

You can build up buildings that resist up to EF3 with poured concrete walls, not cinder block. Beyond EF3 there is nothing you can do except go underground.







/safe_room7_1694.jpg

FEMA
Safe Rooms


More Good solutions for those in Tornado prone areas.


marigolds
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join:2002-05-13
Saint Louis, MO
kudos:2
Even in 250mph zones, FEMA safe room specs only test out to 100mph missile speed on vertical surfaces. You can go beyond FEMA specs up to a 150 mph missile strike rating, but that is as far as anyone goes right now.

The highest spec, FEMA 361 255 mph hurricane zone, is designed for 128 mph missile speed, which is only EF2. Above ground EF3 hardened buildings typically use buffer space (essentially giant safe rooms inside the buildings) rather than building the entire building to withstand EF3.

You can only get higher than that by going underground (which eliminates missile strike ratings). Once you go into above ground, missile strike is going to prevent getting higher.
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alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1
said by marigolds:

Even in 250mph zones, FEMA safe room specs only test out to 100mph missile speed on vertical surfaces. You can go beyond FEMA specs up to a 150 mph missile strike rating, but that is as far as anyone goes right now.

When you say specs to 100mph missile speed, do you mean projectiles going at 100mph or wind?

Wind may go to 250mph, but any real damaging debris wouldn't follow at that speed, hence why 150mph might be okay?

I'm not saying you're wrong, I'm just asking about what the specs represent.


KoolMoe
Aw Man
Premium
join:2001-02-14
Annapolis, MD
Reviews:
·Verizon FiOS
reply to Rob
Wouldn't a pyramid be a somewhat effective design against tornados and such winds? Especially if you could rotate a corner/edge into the wind (assuming wind direction in such storms is relatively directional).
Just a thought. Maybe silly...
--
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natedj
Elected
Premium
join:2001-06-06
Columbia, SC
reply to Rob
A cinder block structure is much safer and stronger that a wood structure if built correctly.
The image posted above clearly shows how not to build a reliable block wall. Building a wall like that will actually cause more damage in a tornado because a flying cinder block is worse than a flying 2x4. That wall has no reinforcement and the cells of the block are not filled. That wall is only as strong as the mortar that's between the joints. Block walls stand up 100% better than wood structures in natural disasters that's why schools are build with them and are considered a "go to" location. I won't dear to call them hurricane /tornado proof but you have a much better chance of survival in properly built block structure.
So why are so many homes in these disaster prone areas still framed with wood? .... its' cost. Not just cost of the block, but and increased cost of labor, cost to fur out the inside of the block with wood for a nice interior finish, cost of windows and doors with deeper jambs, the list goes on.
--
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aannoonn

@optonline.net
reply to Jack_in_VA
After the house collapses on top of your safe room, how do you get out?


marigolds
Gainfully employed, finally
Premium,MVM
join:2002-05-13
Saint Louis, MO
kudos:2
reply to alkizmo
Yeah, that's projectile speed. I think the standard projectile is a 2' 2"x4". (not sure on the length, but it is a 2x4).


mityfowl
Premium
join:2000-11-06
Dallas, TX
reply to Rob
Anybody can make a tornado proof home.

Very few people can afford it.

Back in the early 60's I got hit with one.


XoX

join:2003-08-19
Qc, Canada
reply to natedj
said by natedj:

A cinder block structure is much safer and stronger that a wood structure if built correctly.
The image posted above clearly shows how not to build a reliable block wall. Building a wall like that will actually cause more damage in a tornado because a flying cinder block is worse than a flying 2x4. That wall has no reinforcement and the cells of the block are not filled. That wall is only as strong as the mortar that's between the joints. Block walls stand up 100% better than wood structures in natural disasters that's why schools are build with them and are considered a "go to" location. I won't dear to call them hurricane /tornado proof but you have a much better chance of survival in properly built block structure.
So why are so many homes in these disaster prone areas still framed with wood? .... its' cost. Not just cost of the block, but and increased cost of labor, cost to fur out the inside of the block with wood for a nice interior finish, cost of windows and doors with deeper jambs, the list goes on.

I agree with you... Too many cinder block are laying around without any mortar on them. It look like a poorly built house


KrK
Heavy Artillery For The Little Guy
Premium
join:2000-01-17
Tulsa, OK
reply to Rob
If you put reinforcing steel in them and filled the cinderblocks with concrete, then yeah, that would help.



KrK
Heavy Artillery For The Little Guy
Premium
join:2000-01-17
Tulsa, OK
reply to aannoonn
You wait for rescue.

If you have wired an external antenna you may be able to call for help with your cell phone.


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom
reply to aannoonn
said by aannoonn :

After the house collapses on top of your safe room, how do you get out?

You phone for help. Didn't you notice the phone on the wall next to the flat screen tv?


aurgathor

join:2002-12-01
Lynnwood, WA
kudos:1
Reviews:
·Frontier Communi..
reply to cowboyro
said by cowboyro:

The only thing that will hold against a direct tornado hit is an underground shelter. It's not necessarily the wind, it's also the debris that is like a canon fire against the structure. Do you really think it will hold against a truck that is slammed into it?

A well built geodesic dome should survive any tornado and the usual flying objects.
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panth1
The Coyote

join:2000-12-11
Boca Raton, FL
reply to cowboyro
said by cowboyro:

Tornado vs cinder block structure:

Looks like a cinder block foundation for the crawl space under the house. The floor and walls were probably wood. There would also be a concreate slab not all dirt on the ground.

As to why wood framing is used, my guess is cost and insulation rating. Wood frame construction has a lot more space for insualtion ratings.

Plus these days in Florida, if you built a house out of wood no insurance company would touch you with a 100 mile pole.

robbin
Premium,MVM
join:2000-09-21
Leander, TX
kudos:1
reply to aannoonn
said by aannoonn :

After the house collapses on top of your safe room, how do you get out?

If you actually build a safe room you can usually register it with local authorities. Rescuers will use these checklists to make sure no one is trapped. Here is an example

»www.ci.norman.ok.us/content/stor···stration
Expand your moderator at work

iknow
Premium
join:2012-03-25
reply to KrK

Re: Tornados & House Structure Question..

said by KrK:

If you put reinforcing steel in them and filled the cinderblocks with concrete, then yeah, that would help.


putting up cinder block then filling them is a LOT more expensive than just using poured reinforced concrete. think of all the time it takes just to lay those blocks. also, a poured concrete roof is required for a tornado proof house, anything else would just be ripped right off, taking people with it. the roof is usually the first thing to go on a wood house. experiments were done during the atomic testing, they wanted to see how various building construction held up to an atomic blast. the poured concrete buildings were the only one's left standing. and those were supersonic winds!.

robbin
Premium,MVM
join:2000-09-21
Leander, TX
kudos:1
Do you have anything to back that up? I would question that poured concrete is at all cheap. Cinder block is residential type construction and many contractors know how to do it. Poured concrete walls require a lot form work and is definately commercial work. I would imagine that tilt wall is even cheaper than actual poured walls.

A couple of other things since I haven't posted in this thread. The earlier posted pic of the cinder block foundation failure is just that. That was a foundation to create a crawl space, nothing more. Those were not cinder block walls. The way you make cinder block walls strong is to pour a concrete header. Not just fill them but put a reinforced beam on top. Very strong.


tmh

@verizon.net
reply to Jack_in_VA
said by Jack_in_VA:

More Good solutions for those in Tornado prone areas.

This is pretty cool. How long does the power last? Is that a chemical toilet on the bottom left? I assume the device to the left of the TV is a GSM dialer for the phone.

A reinforced structure like this makes a pretty good all around saferoom. The walls must be thick enough to resist small arms fire.


iknow
Premium
join:2012-03-25
reply to robbin
said by robbin:

Do you have anything to back that up? I would question that poured concrete is at all cheap. Cinder block is residential type construction and many contractors know how to do it. Poured concrete walls require a lot form work and is definately commercial work. I would imagine that tilt wall is even cheaper than actual poured walls.

A couple of other things since I haven't posted in this thread. The earlier posted pic of the cinder block foundation failure is just that. That was a foundation to create a crawl space, nothing more. Those were not cinder block walls. The way you make cinder block walls strong is to pour a concrete header. Not just fill them but put a reinforced beam on top. Very strong.

if you go to all that effort by a skilled mason, just laying the brick, then filling it up with concrete, you're using the same amount of concrete, with a poured wall, you just need a form, and pour the concrete in!. the expense of paying a mason is gone!. and the form is either plywood or the new forms out for the purpose, with insulation and rebar built in.


alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1

1 edit
reply to mityfowl
said by mityfowl:

Anybody can make a tornado proof home.

Very few people can afford it.

Back in the early 60's I got hit with one.

A tornado proof home hit you?

[added smiley to show this was most likely intended as a joke and not trolling - D]


cableties
Premium
join:2005-01-27
reply to iknow
I'm not criticizing block versus concrete. But if it were up to me, Reinforced concrete like bomb shelter/bunker is way to go.

Reinforced block wall is stronger than wood/laminate structure.
Reinforced concrete wall is stronger than block wall.
Cement block is strong than cinder block.
»en.wikipedia.org/wiki/Concrete_masonry_unit

Block walls (aka Cinder block or cement block-there is a difference between the two) even if filled cavities, are typically filled with grout, not concrete.
»en.wikipedia.org/wiki/Concrete

Block walls are cheap way to build a foundation or wall. Today, preformed molds from foam/styrene that can be left for insulation values, are common for poured foundations. It's all about cost savings. Since the sheer and load on most single story isn't that much, a block foundation (crawlspace) may be sufficient. But if you want something tornado proof, I would check with a structural engineer.
»en.wikipedia.org/wiki/Reinforced_concrete
»en.wikipedia.org/wiki/Rebar
»en.wikipedia.org/wiki/Insulating···ete_form

It's not the wind but what is in the wind that also causes the damage (aka projectiles/missiles). And they say its a myth to open your windows to allow pressure equalization. Opening a window means things will fly in.
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Ken
Premium,MVM
join:2003-06-16
Markle, IN
reply to robbin
said by robbin:

Do you have anything to back that up? I would question that poured concrete is at all cheap. Cinder block is residential type construction and many contractors know how to do it. Poured concrete walls require a lot form work and is definately commercial work. I would imagine that tilt wall is even cheaper than actual poured walls.

I guess that depends on your area and if you have basements or not. Around here poured concrete is very popular for basement construction in residential, so it would be easy to find someone to use those same forms and pour a first floor. Block walls at least around here are never filled or have a header on top. Once you factor those in, the poured wall would be cheaper since it's very common, and filling a block wall is not.