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Re: WOOD AND HOUSES

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I reply to the posting:
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> Date: Thu, 30 Jul 1998 18:41:22 -0700
> From: Juan Enrique Justo <jjusto(--nospam--at)copime.org.ar>
> Subject: WOOD AND HOUSES
> To: seaint(--nospam--at)seaint.org


> The several posts (and counter posts) I read about the use of wood in 
> houses construction moved me to ask you what follows.
> Although I?m mechanical engineer, I do love wood, and my hobby is 
> woodworking.

Wood is a beautiful material, especially for furniture and interior 
finishes.  It is also a good construction material as slender sections, glu-
laminated sections, and in veneer sheet forms.  It is also the basis of 
various fibreboards.  It requires special design considerations as expected 
for a material comprising natural fibres formed as a moist composite.  
Engineering skills are required either directly or in formulating non-
specific design criteria.

> But I am not convinced -so far- about the benefits of house construction 
> from wood which seems to be the rule in USA. Here in south america we 
> still prefer bricks.

Are wood (or timber as we refer to the material in New Zealand), supplies 
readily available and economic for house construction in South America 
though?

> I was in Houston for 18 month, and I had the chance to see the progressive
> construction of a condo nearby my place. I saw those tiny (o let?s say 
> slender) timber pieces to be put together to form the structure of walls,
> frames, beams, etc.

The slender timber pieces are joined by nails and fixings, taken together 
with sheet lining and cladding, that make up structural elements that in 
turn make up a house that is weather tight, load carrying and able to resist 
earthquake and wind forces.  The structural performance essence is in the 
energy absorbtion and ductile characteristics of the fixing systems that are 
designed to deform before the wood elements become over stressed.

> I also was told (pls tell me if this is true) that 
> these slim timbers came from very fast growing trees, specially developed
> for construction.

Yes,  in New Zealand, the land of fertile soils, sunshine and rain, this is 
very true.

> I also was told that unless termites choose the same 
> home as you do, this full wood houses can last up to 30 years.

NZ is fortunate not to have termites.  Wood is treated to resist other 
insect infestations, and chemically treated for wet and soil contact 
conditions.

> All this introduction is just to ask to you fellows (ladys included) why
> this wood based system was chosen. Are there some kind of historical 
> reasons?, or may be old traditions? A friend that lives in Tampa Fl, made
> his house to be built up in our traditional way (bricks and more bricks)
> and he had to pay 30% more that a fully wood house. So, Is it because of
> money?

Partly historical tradition and partly money or economics in NZ.  European 
settlers arriving in the early 19th century and developing farmlands found 
vast native forests and so built in wood.  When gold was discovered many 
towns and cities were constructed in masonry brick.  There are good clay 
deposits for brick making.  Strong earthquakes in the late 1800's and early 
1900's clearly showed that wood buildings performed better than the brick 
ones,  so -----

Currently most single family houses are constructed in wood.  They are 
painted (for durability) in many colours and this sets the NZ urban city 
scape apart from many overseas,   even more colourful than the west coast 
US.  We have both light weight (steel/iron) roofs (again in many colours)and 
heavy weight roofs (clay or concrete tiles).  We also use a masonry veneer 
to wood framed, with interior linings, houses so that they look like 
masonry.

Many 2, 3 and 4 storey commercial buildings are constructed in wood, 
particularly those more than 60 years old in smaller towns.  NZ also has 
good natural materials available for reinforced concrete construction and 
this is the common form for larger buildings.  Light steel sections are used 
for industrial buildings.  Larger steel sections have to be imported, so 
only the highest commercial buildings feature steel frames.

Our houses and buildings designed to current standards are expected to have 
good earthquake and wind resistant performance.  Earthquake as good as for 
California.  Wind to hurricane levels!

> By the way, how about New Zealand? What do you use there?

As above.

> 
> Finally, I would like to tell you that this query is just for the sake of
> knowledge.
> 
> thanks
> 

There's a short history of wood construction in New Zealand.  I hope that it 
is of general interest.

Cheers,  Bruce S

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Bruce Shephard, Principal Consultant Seismic Risk
Opus International Consultants, New Zealand
DD Telephone +64 4 4717597,  Fax +64 4 4711397
Email bruce.shephard(--nospam--at)opus.co.nz
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