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Q: rain ( Answered,   0 Comments )
Subject: rain
Category: Family and Home > Home
Asked by: supermal-ga
List Price: $5.00
Posted: 03 Dec 2003 05:02 PST
Expires: 02 Jan 2004 05:02 PST
Question ID: 282979
will the rain decrease the quality of house when the houses are buidling

Request for Question Clarification by blazius-ga on 03 Dec 2003 06:51 PST
Did you have any special kind of building in mind (brick, wood, concrete...)?

Clarification of Question by supermal-ga on 03 Dec 2003 19:47 PST
the residential house in north amercia that builds with wood.
my question is will the rain/snow decrease the quality since the wood get wet?
Subject: Re: rain
Answered By: blazius-ga on 05 Dec 2003 01:41 PST
Hello, supermal,

Yes, rain and snow during the construction of the house might decrease
the quality of the finished house in several ways.  However, there are
ways of avoiding these problems.

My home country, Norway, is a country with lots of rain and snow, and
most residental houses are built with wood.  I checked your question
with Norsk Treteknisk Institutt (Norwegian Institute of Wood
Technology), which is the research centre for the Norwegian sawmill
and timber industry.  They pointed me to two online fact sheet that
describe your problem.  These are in Norwegian only, but I've
translated the key information below.

What are the consequences of incorrect moisture levels?

Wood that is exposed to certain moisture/temperature levels for some
time will start to rot, this process will continue even after the wood
has been built into the house.  At temperatures below +25 (77 F) wood
will not rot if it contains less than 20% humidity.

Another problem is that boards that are fastened while still
containing excess levels of moisture will dry after they have been
kept indoors for some months.  This will cause the wood to contract,
and might cause unsightly cracks or deformations.  Wood materials for
indoor use should only be used when it has been predried to the same
moisture levels that can be expected in their final environment.

On the contrary, wood that is too dry when it is installed might
absorb humidity from the air and start to expand, causing similar


How can correct humidity levels be maintained during the building process?

- Wood material should be ordered with a moisture level that is correct for
  their intended use.

- Wood should not be taken out from its plastic wrapping before it is used, and
  opened wrappers should be resealed after they have been opened.

- The unfinished construction should be protected from moisture by building it
  in a dry time of the year.  If the construction process must take place in the
  rainy/snowy season, a waterproof tent should be erected over the building

- Predried wood boards for indoors use should not be brought to the construction
  site before the building interior is waterproofed, insulated, heated and dried
  to 40-50% air humidity.  Note that fresh concrete will give off humidity for
  some days - avoid opening predried wood in this environment.

- The roof should be constructed in a manner that prevents the outside wood
  panels from direct rainfall.

- Boards on the outside of the building should be waterproofed (painted or
  stained) as soon as possible after installation, or even before installation
  if this is feasible.


I hope this answers your question.  If not, please request an answer
clarification before you go on to rate it.

Request for Answer Clarification by supermal-ga on 06 Dec 2003 18:37 PST
to be prepared for the unpreditable rain/snow, would/should the
builder use some kind of special wood to build the house? if they
don't , wouldn't be most of the houses built of woods having quality

Clarification of Answer by blazius-ga on 07 Dec 2003 04:28 PST
The wood framework of a new house will almost always contain some
excess moisture when the primary construction is finished - that is
when the roof and the outer walls have been finished.  At this stage,
it is common to dry these materials by setting up some kind of air
heater (powered by electricity, kerosene or propane) inside the
construction to heat and dry the wood.

It would, of course, be possible to use wood that is rot resistant -
either naturally (such as sibirian larch) or by chemical treatment. 
However, this will turn out to be quite costly.  Also, some kinds of
the chemically treated wood contains toxic substances (such as
arsenic) which could be undesireable in a residential house.

Where I live, it has also become common to use wood boards that has
been waterproofed (by painting or staining) before they arrive at the
construction site.  These boards are used to cover the outer walls, in
this way the walls are waterproofed immediately.  This procedure can
also turn out to be less expensive than having the boards painted

If there is a significant risk of humid weather when the house is to
be built, it should be considered if a protective tent (as described
in the original answer) should be used.  This will also provide a
better work environment for the people doing the construction work,
and might actually shorten the time needed to finish the house.  I
have seen such tents being used, but I do not believe that they are
very common yet.  I guess most house builders believe that the drying
process (as described above) will remove enough of the moisture. 
There is probably no sharp limit for how long it is "safe" to leave
the wood in the rain before one should cover and dry it.
There are no comments at this time.

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