[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
GSBN:Re: fire test -- your opinions?
If this test was to be performed in Denmark, Norway, or Sweeden I very
much doubt that we would consider using a plaster containing cement.
For two reasons:
1) I cannot recall any SBC in either of these countries using
anything but clay or lime based plasters. So why begin now.
2) we can only fly as high as the dreams we dare to live, or smth
similar.... My point being, that IF a 2 hour earthen plastered wall
passes the test, that will impress and create possibilities for years
to come all over the place.
Experiences from firetests:
<a target="_blank" href="http://www.baubiologie.at/download/zertifikate/F90.html">http://www.baubiologie.at/download/zertifikate/F90.html</a>
This Austrian certificate shows the successfull 90 minute test of a
SBC plastered with lime on the exposed side, and earthplaster on the
unexposed side, using 20mm of plaster on both sides.
The succesfull Danish firetest of an earthplastered SBC was only 30min
long. A few things might still be worthwhile noticing:
- the average as well as maximum temperature rise on the unexposed
side after 30minutes of testing was 1 (one) degree.
- one of the criteria for failing the test is that the surface behind
the exposed plaster is charring. The normal procedure to determine
whether this has happened is to chip away the plaster in 1-3 spots. As
none of these spots showed any charring, the person in charge of the
testing (who didn't much fancy SBC), ordered his men to remove the
entire surface of plaster (2,4x2,4m). Unfortunately I was not present
during the test (although I build and plastered the wall), but i have
been told by eyewitnesses that it was not an easy job to remove the
plaster. To say the least.
- two 100x100mm timbers had been placed flat with the exposed plaster
surface to simulate the by far most commonly used SBC in Denmark, the
post and beam infill SBC with earthplaster. The hope was to be able to
estimate the burning of the posts set in the plaster, to be able to
calculate dimensions better. Expecting the plaster to chip away on the
sides of the posts, thereby being exposed on three sides, it was
feared the posts might possibly totally burn away if we went for 60
minutes, leaving no evidence to make calculations from. As it turned
out the plaster stayed intact, and the posts only burned from the
exposed front. The loadbearing wall (with the two posts looking like
infill) was not compressed.
- the person in charge of the overall testing programme (fire,
insulation, moisture, sound, mold and more) has been following the SBC
in general for minimum 5 years. Having written the Danish report with
resumes of all the tests as well as recommendations regarding how to
build with these results in mind, and having read a lot of the
testresults around, I think he is the most qualified person to hold an
opinion on this matter in Denmark. And although his speciality is not
plasters, this is his opnion on testing an earthplastered SBC:
a) the Danish test would most definitely have done well around the
posts if it had gone for 60minutes instead of 30minutes.
b) with uninterrupted earthen plaster straight unto the plaster
120mins is not unrealistic.
c) It is possible that plaster containing cement will flake off
earlier than clayplaster will, due to the fact that chemically bound
water is released from concrete when heated. The force of the steam
then causes the flaking. Earthen plaster is more open, so the steam
can get out, and it happens a lot earlier, as the water in earthen
plaster is not chemically bound.
2006/4/27, Rob Tom archilogic@...:
Bruce, King of Sausalito wrote:
GSBN is an invitation-only forum of key individuals and representatives of regional straw construction organizations. The costs of operating this list are underwritten by The Last Straw Journal in exchange for use of the GSBN as an advisory board and technical editing arm.
For instructions on joining, leaving, or otherwise using the GSBN list, send email to GSBN@...HELP in the SUBJECT line.