[GSBN] SB Overhangs (was Big News!)
Andy Horn
andy at ecodesignarchitects.co.za
Wed Aug 25 20:36:47 UTC 2010
Hi Martin
I certainly don't envy those trying to create a 1 size fits all
international building code that balances freedom of design and place for
innovation with the specifics of good building practice. Anyhow to add some
further food for thought.
In answering questions about what to do with multi storey designs, I always
find history to be such a valuable tool when it comes to looking at various
design responses.
The vernacular architecture of Japan has evolved a very sensible
architectural style when it comes to protecting their thin little earth
plastered wattle and daub structures. Numerous numbers of these structures
still exist with some are many hundreds of years old, with some being even 3
or 4 storeys high of earth plaster!! The roofs are often but not always
hipped, affording good overhangs all around and in the case of multi storey
buildings each floor has its own min roof around it like skirts..so shedding
the rain at each level. In the case of gabled wall ends, all the openings
have min roofs over them. Other times the clay wattle and daub is given a
basic plaster and then an external timber siding rather than more plaster is
used. Effectively parapet walls are generally avoided so the roof always
closes over the top of a wall. Even their boundary walls, which are usually
of more solid packed earth and are typically earth plastered, all have mini
roofs over the tops of the walls ..usually 1 layer of beautiful crafted fire
clay tiles overhanging either side with a ridge cap in the centre. Their
plastered walls are also broken into panels with expressed timber framing,
so that the plaster surfaces are broken down into manageable sizes that can
be plastered to absolute perfection and generally present much fewer
problems with cracking.
I am not familiar with the extent or wording of the code, so I may be
speaking out of context but generally I would be worried about being overly
prescriptive about how one solves a problem ....especially where officials
can take a narrow interpretation of a code and there may be ways and new
products that have not been thought of yet that may offer alternate
solutions? While I agree having roof overhangs is best practice and I have
not done otherwise, it may be wiser that one set about defining what one is
trying to do that a roof overhang is doing.i.e. not letting water get in
from the top being the most critical clearly... or is one trying to give the
wall some degree of protection from rain hitting it by using an overhang as
well? Because outright protection I don't believe is practical or even
necessary. I think the degree or amount of overhang is more of a regional
thing that is even specific to the exact context of the site of the
building. the intensity of rain that is potentially hitting a wall and the
direction that it comes (rain does not always come from above) are clearly
important factors to try and understand and respond to and will vary from
place to place.
Context will change things and how one designs in relation to the context
...so I would imagine some of what the code needs to address would be how
design may respond differently in relation to the amount of rain, wind
direction, wind driven rain (if applicable), rain intensity, when it rains
in relation to how cold or hot it is, so one understands how quickly or
otherwise rain may be able to dry out again. The position of ones overhangs
and rain buffers (pergolas, shade devices etc) and use of rain screens may
be of more importance depending on where and how big one designing..the rain
here in the Cape is typically winter rainfall that is wind driven almost
always coming from the North west..and in some cases comes in horizontally
especially along the coast. In these cases one has to look at incorporating
siding over the bales and rain screens on the exposed sides to help shield
the rain..and in certain cases I will avoid using straw in the parts where
it is too at risk..so I rarely end up with a building with 100% of its walls
being in straw bale.
Best
Andy Horn
ECO DESIGN - Architects & Consulatants
6th floor, 79 on Roeland, 79 Roeland St.
8001, CAPE TOWN, SOUTH AFRICA
Tel: 07 21 462 1614, fax 07 21 461 3198
website: www.ecodesignarchitects.co.za
_____
From: GSBN-bounces at greenbuilder.com [mailto:GSBN-bounces at greenbuilder.com]
On Behalf Of martin hammer
Sent: 25 August 2010 02:50 PM
To: (private, with public archives) Global Straw Building Network
Subject: Re: [GSBN] SB Overhangs (was Big News!)
Hi Graeme,
I'll send you the SB code off list.
Re: the overhangs, what do you do with multi-story or tall walls? Do you
have roof at typical first floor ceiling height in addition to the upper
roof?
I will definitely consider putting such a table into the SB code. I saw
Bruce's vote of agreement, and wonder if anyone else strongly agrees or
disagrees that overhangs be code-mandated for strawbale.
Overhangs are generally a very good idea for SB, and I consider them "good
practice" or "best practice". I don't know if they are at the level of
"minimum practice", which is typically the threshold of code language,
although all of that is open to considerable debate. Also in your table
you account for wind as a factor, but not rainfall. If your table were
applied to desert climates, it might be unfairly restrictive (although some
desert climates receive concentrated periods of rain).
In an earlier iteration of the code I prohibited strawbale parapets, but for
a few reasons decided to instead be silent on the issue.
Martin
On 8/24/10 4:11 PM, "Graeme North" <graeme at ecodesign.co.nz> wrote:
HI Martin
firstly my congratulations -
and yes, I would really appreciate a word document I can make comment on
>From my neck of the woods, one of the overriding issues I encounter time
and time again is that of good weather protection from wind driven rain in
our decidedly pluvian and humid climate - something that gets skittered
around in most books and references.
I think we need a prescriptive starting point. In the NZ Earth Building
Standards NZS 4299 we relate wind zone. eaves height (vertical exposed wall
height), and roof overhang width to give MIMIMUM roof overhangs as follows
-
Wind Zone - Ratio of eave height to width
Low (at ULS 32m/s) 4:1 (600mm over a 2400 wall)
Medium (37m/s) 8:3
High (44 m/s) 3:2
Very High (50 m/s) 1:1 (or in other words a full verandah)
We developed this table after leaks and some degradation of material in some
earthen structures and I can report that there has been no reported problem
since we adopted this.
It is my contention that straw buildings are at least as moisture sensitive
as earthen buildings and I would suggest that this sort of table be regarded
a good starting point for calculating minimum roof overhangs for
direct-plastered external strawbale walls, a recommendation that could
possibly be worked back (or exceeded) after local weather or site
assessment, or possibly a service history of locally developed techniques.
It may seem a but draconian to some but for my money the biggest problem
with strawbale buildings, in humid wet climates at least, seems to be that
of providing adequate primary weather protection, in the form of eaves, or
rain screening, and lack of good practical prescriptive guidance on this
subject.
Comments welcome
Graeme (in bossy standards writing mode) North
Graeme North Architects
49 Matthew Road
RD1
Warkworth
tel/fax +64 (0)9 4259305
graeme at ecodesign.co.nz
www.ecodesign.co.nz
On 23/08/2010, at 5:32 PM, martin hammer wrote:
Everyone,
Lars Keller asked the below question so I thought I would answer to all in
case others are interested. I'll set a deadline of September 30th for
anyone wanting to comment on the strawbale code as in the second draft of
the IGCC.
Thanks.
Martin
On 8/22/10 9:36 PM, "Lars Keller" <larskeller at gmail.com> wrote:
Dear Martin,
What is the deadline for comments to you ?
Best regards,
Lars Keller
On 22 August 2010 03:36, martin hammer <mfhammer at pacbell.net> wrote:
Hello friends on the GSBN,
My voice has been conspicuously absent on this subject, so I thought I
would weigh in.
First, thanks for the words of appreciation. I was pleasantly surprised to
hear the news from David on Monday. I think this strawbale code document is
very good, but there are a number of reasons I didn't think it would go
through to the next step. I thought both the Earthen Materials proposal
(referencing the recently revised ASTM standard that Bruce, David in earlier
years, and others worked so hard on) and the Straw-Clay proposal I
co-authored with Paula Baker-Laporte, had better chances. I might propose
them again in the upcoming Code Change Proposal phase (once IGCC committee
concerns are addressed).
Much blood, sweat, and a few tears have gone into this SB code since 2003,
when I began writing it at the request of the State of California (they
asked Bruce, Bruce asked me . . .). I've had very good input from others
along the way, including members of this list (David Eisenberg, Bruce King,
Dan Smith, Bob Theis, Tim Kennedy, John Swearingen, Bill Steen, Kelly
Lerner) (apology if I've missed anyone), and others not on this list,
notably civil engineering professor Mark Aschheim.
Because it started as a California code, and because there are great SB
experts in northern CA where I live, the code might be a bit
California-centric (with particular attention to seismic issues). However
I've always wanted it to be broadly applicable and I welcome broader, global
input at this time. I expect to propose adjustments during the next IGCC
review phase. If it remains in the IGCC and goes the way codes often do,
some version of this might show up at your building official's door and then
your strawbale door in Australia, South Africa, or who knows where. And
although I think there's much to like, I can almost guarantee you can find
something you don't like. So . . .
If you want to see and comment on the proposed code you can ask me to
e-mail the proposed SB code (by itself) to you as a word document, and then
e-mail me your comments or send it back with "track changes". OR you can go
to: http://www.iccsafe.org/CS/IGCC/Pages/Comments0810.aspx , and download
all Public Comments under the "Complete Document" subheading (Strawbale
Construction is Comment #5-136). You can then e-mail your comments to me
(not to ICC). I'm also open to comments on #5-134 Straw-Clay, and #5-135
Earthen Materials. If you want to understand the IGCC process and schedule,
you can go to:
http://www.iccsafe.org/cs/IGCC/Pages/PublicVersionDevelopment.aspx
In addition, I want to clarify that:
* Strawbale is not yet in the IGCC. That's because it isn't finalized
(and SB could even be entirely removed).
* Even if included in the final version, the IGCC applies only to
commercial and high-rise residential, AND only in jurisdictions that adopt
the IGCC. So it would have limited application.
*
That said, this approval is still a very good thing. And if it does make
it to the finish line of the IGCC, it would probably then migrate to the IBC
in the next code cycle, and then to a jurisdiction near you. I even see the
possibility of jurisdictions adopting it or informally using it for all
occupancies, even before reaching the IBC. John Swearingen's report of it
already producing "instant results" for his project in Stanislaus County
supports that notion, and is both welcome and frightening.
Finally, I want to acknowledge David Eisenberg and Matts Myhrman who
together forged the first SB code in Arizona in the early-mid 1990's, and to
David again for speaking so convincingly on behalf of the current proposed
code at the recent hearing in Chicago. If you read his description of what
he said, you'll see that he simply told the compelling truth about the most
relevant issues. It's one of many things David does so well. It's nice
when the compelling truth prevails (at least for now).
Thanks David, and thanks to all. And thanks to the enduring spirit of
strawbale!
Martin
PS - For a pre-IGCC history of this SB code, see my GSBN post on Dec. 1,
2009. Reviewing that e-mail might also be used as a natural aid to help you
fall asleep. However, for me it is a riveting drama (sometimes moving at
the pace of a melting glacier . . . actually that's happening quite quickly
these days!)
On 8/16/10 10:13 PM, "strawnet at aol.com" <strawnet at aol.com> wrote:
Hello all,
I want share some great news. Earlier today, here in Chicago, Martin
Hammer's "comment"/proposal to include the strawbale code he's been working
on over the past few years in California into the new International Green
Construction Code (IgCC) was approved by a committee vote of 8 to 6! The
IgCC is the new US code for commercial (and high-rise residential) buildings
that will become part of the family of 2012 International Codes (I-codes).
It will go through a full code development cycIe with the rest of the 2012
I-codes next year and there is work that will need to be done still to make
sure it doesn't get rejected in that process, but getting it into the second
public draft of the code now is a very big step forward.
I served on the drafting committee for this code from last summer through
the spring of this year. For more information about the IgCC and to download
the whole IgCC first public draft and the comments - including Martin's
proposals for strawbale and earthen building and the EcoNest comment in
support of straw clay go here:
http://www.iccsafe.org/cs/IGCC/Pages/default.aspx
http://www.iccsafe.org/CS/IGCC/Pages/Comments0810.aspx
You'll find these listed as comments 5-134, 5-135 and 5-136.
I was the only proponent speaking in favor of it here, and there were
others who spoke in opposition. The initial motion was to disapprove but it
failed 5 votes to 9 after considerable and very mixed discussion - which
surprised me because of the nature of some of the comments - that it was
still not ready and needed some technical fixes.
The failure of the motion to disapprove required a new motion and Chris
Mathis, an old building science friend from North Carolina, offered a motion
for approval. That was followed by more discussion, with more concerns
expressed that it wasn't ready. Then, just before the second vote, Chris
pressed the committee to push the envelope. He said they should approve it
and get it in, and rather than just having the few people who are very
knowledgeable about it work on improving the things that still need to be
done, "Let thousands of people look at it and help improve it through the
next round of the code development process!" He said it was time to start
pushing these things through. Then they voted - and it passed 8 to 6! I was
amazed and delighted! So it is going into the second public draft!
There were two other similar proposals (they're called "comments") that
were heard right before the strawbale comment. The first, from Paula Baker
Laport and Robert Laport proposed including the straw clay guidelines from
New Mexico. Next was the other submitted by Martin, that one in support of
earthen construction based on the new ASTM standard for earthen wall systems
that I had initiated almost 10 years ago and Bruce King has spearheaded over
the past few years. I spoke in support of both, but they were disapproved,
though both received encouraging suggestions to bring them forward again
after addressing non-mandatory/permissive language and other issues.
Because they were heard one after the other, and I was the only proponent
for them, I got to speak first for each one and so I had a total of 6
minutes (2 minutes each) to frame them all in terms of the big issues I've
been speaking to for all these years, including the coming challenges of
ever-more limited and expensive energy, the low-impact, low-tech, climate
beneficial, local/regional benefits, the industrial/proprietary bias and
difficulty in funding research, testing and development for public domain,
non-proprietary materials and systems. I started off by talking about the
fact that I had been in buildings in Europe built with materials like straw
clay and earth that are twice as old as this country! And to say that these
are durable and safe ways of building when done properly. And when talking
about the ASTM earthen standard, I said that if they looked at it they might
think that it was too low tech to be reasonable compared to the standards
that they're used to for concrete and other industrial materials. But, I
said, It was intentionally low tech. That I was involved in initiating that
standard almost ten years ago and it was both to enable the use of those
materials here and to reverse the outlawing of earthen building in
developing countries through the adoption of modern industrial codes. That
it was designed to enable people to build safe, durable, healthy, and
affordable buildings anywhere in the world-including the in United States. I
mentioned that the committee that developed that standard included the
leading experts on earthen building and engineering from around the world
and was based on reviewing and incorporating the best from international
codes and standards for earthen building.
After the first two went down, I was quite convinced because of the
comments that the sb proposal would share the same fate and, thankfully, I
was wrong!
So hats off to Martin, Bruce, Matts, and many others who have worked so
long and hard to develop these codes and to Chris Mathis for his leadership
and visionary action on the committee.
Onward!
David Eisenberg
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