What is the safest home structure, 2x4, cinder block, adobe, concrete, rammed earth, bamboo, or log?

Question

or log cabin? Safe in general, meaning resistant to fire, termites, earthquake, flood, tornado, etc.

Answer 1

Well, okay. Safe in general, including tornado, I'm going to have to go with concrete.

Here's the deal, a F5 tornado can pull the grass out of the ground, so there is a great deal of uplift you need to resist in this context. Wood just isn't going to be connected well enough no matter what your wall system is. I would say precast floors and roof, with masonry or concrete walls. Obviously connection between the floors and roof and walls is the main concern here, but the weight of the roof helps keep it on during the tornado.

In a practical sense, the chances of getting hit by a tornado is realistically zero, but the consequences of getting hit by a tornado is of course, catastrophic.

There are no design standards or references for tornado resistant shelters I know of, although there is a chart in the ASCE 7 showing a 300 mph design wind speed for a tornado, as well as a geographic region of the US where it applies, with a one in 10,000 years recurrence (for reference normal wind speed of 90 mph in the continental US is most common, especially in the midwest, with a recurrence interval of 50 years). I think concrete or masonry/concrete are the most likely to be workable with minimal changes to construction for 90 mph winds.

The connections would also be critical for the earthquake loads, but concrete (or even steel) are inherently fire and termite resistant. I think a steel structure could be equally safe, but you would need to be a lot more material than a typical 90 mph design speed steel frame to deal with the extreme uplift caused by 300 mph winds.

Rammed earth or adobe could probably be as termite and floor resistant, but the tornado uplift and the roof to wall connections probably cannot be made strong enough (as a practical matter).

Flood tends to be a foundation problem, and since basically all foundations are built from concrete isn't really part of the question. There are permanent wood foundations popular in the Southern States of the US, but the termite question as well as long term flood survival boot them off the list for my thinking.

Answer 2

On the island of Taiwan, where they have many serious earthquakes, and windstorms, many of the homes are constructed of reinforced concrete.
If I had my choice of construction to meet the most threats, that what I would choose.