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GSBN:from bruce king / fire test: here's the plan ---
Greetings, everyone --
First of all, many thanks again to everyone who responded to my request
for opinions about the forthcoming ASTM (American) fire tests. I have
never seen so much activity on this list since its inception, which has
only now finally died down. Y'all have a lot of opinions! (as do a
number of other people who have written to me off-list), and yet with
very few exceptions they were all thoughtful and useful. (Tom Hahn and
others who have just joined: welcome! and you missed a lot -- see the
archives if you're interested.)
The test is ASTM E-119, and is very tightly prescribed:
1. you burn a very hot flame for two hours on one side, and the other
side cannot get hot enough to ignite loose cotton, immediately followed
2) hosing the wall for two and a half minutes, moving a medium-strong
hose stream back and forth and up and down across the exposed 10' x 10'
[3m x 3m] wall surface to simulate the actions of firemen; if the
water squirts through the far side, you fail.
So you're probably wondering what, after all that, we're going to test.
(For those who want to read that far, below you can find the line of
reasoning that underlies these decisions, written by David Eisenberg
and me in various messages of the past two weeks.)
And now, being from California, home of Hollywood, the Grammys, the
Bammys, the Webbies, the Golden Globes, the Silver Spades, the Brass
Bozos, and of course the Oscars, I have to here put on my sunglasses,
adopt my best Jack Nicholson persona, and stride confidently out onto a
brightly-lit stage with stunning grin and envelope prominently in hand
to announce the Winners (as cameras flash to audience celebrities, with
gowns, makeup, cleavage and jewelry any of which would pay for 100 fire
tests) . . . the envelope please . . .
We will test two wall assemblies:
1) a "must-pass" (MP) wall and
2) an earth-plastered (EP) wall
Must Pass wall
- 16" x 18" x 36" 2 (polypropylene) string wheat bales on-edge
(on-edge because we figure that would open the door to using bales
flat, where the reverse wouldn't be true).
- 2x wood surround built into the lab's test frame to receive 16 ga
mesh staples @ 6" oc, and 17 gage galvanized stucco mesh (without the
paper or standoff spacers). This (mesh) is probably the most
controversial part. But David and I sensed that, even though the
chance is very small that a meshless wall would fail the hose test, we
can't risk it -- this is the must-pass wall. Do not through-tie the
mesh, just use robert pins as needed to hold it in place. Overlap
adjacent mesh sheets six inches.
- 1" scratch coat of lime-cement plaster, VERY well worked into the
straw; minimum 1 part hydrated lime to 6 parts cement, sand about 6
parts. (1:4:6 would be even better, ie more lime) Whatever we use,
we'll record the ingredients (including water) and proportions.
- scratch well, then cure under plastic sheeting right up against the
face of the plaster, no need to add extra water
- after 7-10 days, remove plastic, hose lightly, add a 1/2" brown coat
of same plaster, cover with the plastic, have a beer. Remove plastic
after 14 days or so.
- schedule burn for 28 days (minimum) after brown coat is applied.
Earth Plastered wall
- 16" x 18" x 36" 2 (polypropylene) string wheat bales flat.
- 2x shaped wood wedges driven between the top (and one side) of the
bale assembly and the lab's frame. This is to put the squeeze on the
wall so as to hold it in place, especially under hose pressure. Use
lots of wedges, from both sides, don't be shy.
- 2" single coat of sprayed (courtesy of Frank Meyer) earthen plaster.
Consider applying a light coat to the first side, having two guys/gals
trowel it into the straw real well while pre-spraying the other side,
then come back and finish the coat (repeat other side). I can't
emphasize enough that, with both tests, I sense that working the first
layer of plaster deep into the straw will be crucial to our success.
- Frank and David will design the mix.
What were we THINKING????
We fully recognize that for most of the builders and designers on this
list, the projects they do don't require a fire rating. And so, other
than the potential benefit that will likely result in gaining
acceptance with insurance companies, and the ability to further
reassure clients about the fire safety of bale structures, these two
tests will be relatively insignificant for those doing primarily single
However, more and more of us in the US have been getting involved in
larger projects for schools and other commercial or institutional
buildings. These buildings almost always do have fire rating
requirements and they are also more likely to require highly durable,
lower maintenance wall finishes that can be reliably applied with
fairly certain performance in terms of durability and cost. Thus the
interest and need to have available test results for cement-lime
plasters - which meet those particular characteristics with far greater
regularity than either lime or earthen plasters in their current state
of development and use in the US. This is not a knock on anyone - just
an observation of mine [David Eisenberg] that has been reinforced by
conversations with numerous others who are struggling to get these
systems to a point where they are commercially viable, cost-effective
and reliable enough for the people who must take on the liability of
doing these types of buildings.
The research carried out by John Straube, showing the remarkable
increase in water vapor permeability of cement-lime stucco resulting
from the addition of more lime has reduced some of the concerns about
moisture management in these types of assemblies, as well. (See the
research results on the Ecological Building Network website
www.ecobuildnetwork.org). None of this denies or dismisses the issues
surrounding the environmental impacts of portland cement including its
contribution to global warming (which probably everyone on this list is
aware of already -- no need for lectures, thank you). This is just
where we are in the current state of evolution of this building system.
And it's worth noting that the climate impacts from the production of
lime are not insignificant either.
It is also worth noting that we've also heard from others who contend
that the inclusion of a test of earthen plaster on straw bale has
little practical value at this point in time -- including from many who
passionately use and promote earth plastering). Their reasoning is that
the buildings that could most benefit from this don't require a fire
rating in the first place and the buildings that do need it are
unlikely to be using earthen plaster for durability and maintenance
reasons -- and that not that many people know how to design, mix, apply
and cure earthen plasters well. For example, this quote from a list
member with a LOT of SB experience:
" After 100,000 sq ft + of plaster application on bale walls since
1995, nearly 98% is the standard cement/lime stucco. There is little
call for earthen plasters or soil cements once the buildings are over
600 sqft in floor area. I wonder where all the interest in adobe
finishes comes from given the general lack of interest in this region?
One reason may be the simplistic and misleading information published
on using earth plasters; this is the "just slap some mud on the walls"
school of thought. Kelly Lerner asked for opinions on a chapter on
plasters she contributed to a colleague's book. I had to point out she
over simplified the amount of prep work needed to gather, transport,
screen, store and use an earth-based plaster. She agreed.
In discussions with Bill Steen on the appropriateness of earthen
plasters for contemporary north american homes and businesses, we
agreed some critics of "concrete" plasters did not know stucco is a
cement lime mix. When a client inquires about an earthen plaster for
their bale home I ask them if they have a boat and what material is
used in its construction. Nearly all the boats mentioned are made of
plastic and they realize they already made a choice for strength,
longevity and low maintenance. If they love to do brightwork on their
sailboat, kayak or canoe, then they can appreciate the labour of love
and effort needed to care for the walls of their home. I say this as an
avid wood boat junkie who enjoyed the yearly ritual of refinishing two
cold moulded wood kayaks and two sailing dinghies I built.
If plastered straw bale buildings are a tiny boutique market, then the
earth plasters business is a boutique within that boutique. As the
projects become larger, see www.pigeoncreek.ca, and developers inquire
about adding plastered bale homes to their offerings, then it better
serves our goal of mainstreaming SBC by connecting with the best of
existing building, insurance and financing practices and meet the
highest standards of fire safety."
I [David Eisenberg] confess that I was glad to see the widespread
support for testing an earthen plastered wall for many of the reasons
stated in all those messages to this list. But for me there is an even
bigger reason behind testing an earthen plastered wall in addition to a
cement-lime plastered wall. Here is part of my contribution to that
"The other factor that weighs heavily in favor of testing an earthen
plaster wall is the same that motivated my initial efforts in trying to
develop "appropriate" ASTM standards for earthen architecture, and
which also motivates Bruce's current efforts in that realm, which is
the degree to which US standards, codes, test results, etc. have weight
and credibility elsewhere, especially in developing countries. Knowing
how much trouble advocates around the world are having in gaining
approval for any earthen building, or alternatives like straw bale,
earthen plasters, etc., and how much acceptance in the US makes these
things acceptable elsewhere, I think this test is important. It will
also, assuming of course that it is successful, open the door for much
more use of earthen plasters here in this country, including in some
applications that may be fairly "boutique" in the large scheme of
things at this point in time.
And things are going to change pretty drastically at some
not-too-distant point in time as petrol and climate realities become
more and more evident and our options and ability to use whatever
resource- and energy-intensive thing that we like become less and less
viable. A lot of these things that are niche status today may become
much more mainstream sooner than we imagine and it would be very good
to have such test results to point to when things start to shift,
rather than scrambling to find the resources (not to mention the
natural gas to fire these walls) at that point...Anyway, that's my
thinking on it."
Bruce chimed in with this: "I believe that IF an earth-plastered wall
can pass the test (not by any means certain -- the fire's not the
problem, but the hose test scares me), then we will have leapfrogged
forward, so to speak. The benefit would accrue not just to the
EarthFirst! crowd of baleheads, but in oblique ways bolster the
acceptance of earthen construction in general -- something I very much
want to do. And, as David said, we ain't gonna have cheap oil in the
very near future, so let's take the long view and plan ahead."
So, for big reasons and current realities, we're aiming to satisfy both
of these needs in the most careful and thoughtful way we can. We would
love to be in the position to conduct many more tests and hopefully we
will, but in the meantime, we're going to make sure we do whatever we
can to get one and hopefully two successful 2-hour full scale fire
tests done. That would lay to rest any questions about fire safety for
almost any type of occupancy for which we envision bale walls being
used. And this will cap the suite of tests that Ecological Building
Network oversaw with funding from the State of California...all of
which will be available in the book Bruce is working on as well (as
well as on his website).
Thanks!! Good night!! I don't want to talk about it anymore, OK? If
you have any further comments, questions or suggestions, please send
them by regular mail, along with your contribution of no less than 100
USD, to the address below. If you want to SHOUT, or lecture me about
what a bonehead cement-lovin' Murrican no-nothing engineer I am, then
please accompany your missive with a contribution of no less than 500
USD. I'm all ears.
Thanks!! Good night!! See you soon!!
Bruce King, PE
Director, Ecological Building Network ( www.ecobuildnetwork.org )
Publisher, Green Building Press ( www.greenbuildingpress.com )
209 Caledonia St.
Sausalito, CA 94965 USA
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