house building in the USA

[Marshmallowman]

This has always had me a bit perplexed, when seeing storms/tornadoes hit the USA you see huge amounts of splintered wood and mostly softwoods at that.

Is there a reason they stick with that kind of construction?.
I know in a earthquake area it makes a lot of sense to stick with wood, but is tornado zone prone to eathquakes or is it becasue its of cost or Historical reasons?

Here in Western Australia brick is pretty much standard, (less so in eastern Australia)

In the northern part it has to be certified able to handle cyclonic winds(hurricane) 376kmh in the coastal area and 280km for less prone areas for all new builidgs.
Caravans legally have to tied down in cyclone areas by steel cables as well.

That said the most of the southern part do not have or need those standards.

Admittedly Australia is quite young as a nation so we have less legacy issues, most of standards were updated after the city of Darwin was pretty much wiped off the face of the earth during cyclone Tracy.

We also have some of the most deterimed termite breeds. Building a wooden house frame in the northern part of Australia is pointless(even the best hardwood we have Jarrah), It will be eaten by termites within a couple of years unless you have some heavy duty barrier protection, eg metal stilts. And even then the sneaky buggers make sand tunnels up and they go straight through concrete and brick like butter and eat house wiring for desert.

You can't use standard insecticides either, the only thing that kills them is arsenic and other banned chemicals. (The breed that makes mud mounds a couple of meters high)

PS I grew up in cyclone rated fibro house, corrugated iron roof bolted down with iron batterns, on steel struts.( cheap but strong)
I slept through a 324 kmh cyclone in that house.(well thats when the weather bureau wind speed meter blew away)

[Brian Ellis]

Traditionally, here the houses were mud/straw bricks or sandstone blocks, depending on the wealth of the owner. In 20th c, these were replaced by terracotta bricks, but these were catastrophic re quakes, which are quite common

The typical approved construction is a reinforced concrete raft anchored to bedrock or with 3 m deep inverted mushroom-shaped anchors in soil if bedrock is not feasible. A reinforced concrete skeleton is fixed to the raft with 20 cm pillars on a 5 m x 5 m maximum base. Upper floors are affixed to this skeleton. If the roof is flat, this has also to be a 15 cm concrete platform. If it is not flat, the skeleton terminates along the roof ridge in a heavy concrete inertial beam (the one in my house is 50 cm deep x 35 cm wide section). The spaces in the skeleton are filled with terracotta bricks. This construction is supposed to cause little danger up to Richter 6.5 with the type of temblor most common here. Mine has withstood 5.5 with no damage and 4.5 with shallow epicentre (5 km depth) at 7 km distance and largely horizontal movement.

In recent years, a number of timber frame houses have been built and a few steel frame ones, for cheapness and better insulation, but we don't have sufficient data on how well they withstand quakes and weather extremes but there are termite problems. I understand the wooden ones are not designed for a lifetime of more than 20 years, where the traditional skeletal ones are ok for >50 years with correct maintenance.

[degrub]

because - nothing short of a reinforced concrete shelter or a steel box anchored in concrete will stand up to high tornadic winds ( 440 kph +) and the resulting forces from all angles.
- low probability of actually getting hit
-likely to be able to shelter underground out of the wind force.
i have been through 3 close ones - less than 200 meters - sitting in a storm shelter (2) and directly under one that skipped over the residence - a weak one, no doubt, probably F2 or F3.

http://www.tornadoproject.com/fscale/fscale.htm

Our building code only requires designing for about 200 kph in high wind areas for cyclones. Some districts have adopted slightly higher. Other areas of the country, the design wind load can be as low as 155 kph The key thing is keeping the building envelope intact - debris through windows or a poorly attached roof joint will cause the building to come apart. THe walls are plenty strong to withstand the wind pressure from even higher winds in a cyclone.

Tornados have a tremendous amount of debris once they are on the ground - hence the windows are blown out and the envelope compromised = exploding building.

[Jammrock]

A lot of it is economical. Most areas have brick layer unions that set some astronomical price just on laying the brick. In KC it was $23 per square foot, and that did not include the mortar or brick. At that cost it adds 50%-100% on to the cost of the average size home.

And as degrub said, not much stands up to a tornado. Best have a basement or a storm shelter if you live in tornado alley. It's really the only safe place to be. A 2x4 caught in a tornado wind will go through just about anything, even a brick wall.

[Dr Mordrid]

What Jammrock said - US "Tornado Alley" twisters are often referred to as 'the hand of God', and sometimes one large funnel cloud will contain several vortices orbiting each other. Mile wide effing Mixmasters that can rip a whole road bed right out of the ground to bare Earth (seen it happen) and worse. Definition of the EF numbers is by damage. The definition of an EF5 is;

Total destruction.

Strong frame houses leveled off foundations and swept away; steel-reinforced concrete structure badly damaged; high-rise buildings have significant structural deformation.

[Jammrock]

All this tornado talk reminds me of an old Kansas joke.

How can you tell if someone is a native Kansan?

When the tornado sirens go off an outsider will run and hide, a native goes outside and looks for the twister.

[Dr Mordrid]

Wrong headed, but about right with one addition; they hunt down their video cameras first.

[Marshmallowman]

Makes sense. A Brick house might just provide more and lethal ammunition for it.
Tornado's are one of the freaks of nature you want to see and not see at the same time.

[Dr Mordrid]

Give you an example of how useless even concrete is in a big twister.

One of our neighbors had a barn which had 2x2x4 foot cast concrete block construction for the lower 10+ feet, and even larger ones were used for the 4 foot deep foundation. These were all drilled so you could tie them together with #9 rebar or long bolts and a hydraulic cement adhesive. Strong structure, and heavy as hell.

Stood up to everything until an F4 (old Fujita scale) hit it head-on. NOT ONE block was in place after the twister hit - they were scattered over almost a quarter mile of his fields and some of our fields, and some were nowhere to be found. Took a lot of man-hours, 2 big truck wreckers with extendable booms and a huge flatbed to haul them out.

Best place to be when one of our tornadoes hits is damned near anywhere else.

[Tjalfe]

One of the main reasons for wood construction here, is to be able to fit enough insulation in the walls. Also, historically, there are a lot of trees around too