[GSBN] SB Overhangs (was Big News!)

Thu Aug 26 11:03:17 UTC 2010

Re: [GSBN] SB Overhangs (was Big News!)Hello all,

again compliments to all this great work which in essence should make things easier by systemized solutions. If I read Andys remarks on freedom of desgin we might be able to solve the paradox of securing people from design failures and at the same time stimulate ongoing experiments by a simple preamble for codes: ."this or better". 

This would be an opening to convince building inspectors for what's not be known yet, but definitly soon will be offered. Without flexibility there is just little innovation. And it is the "cemented aspect" of the building industry which spends a minimum for innovation in comparison to other sectors. 

Best wishes from a rainy Brittany,

Martin Oehlmann

----- Original Message ----- 
  From: Andy Horn 
  To: '(private, with public archives) Global Straw Building Network' 
  Sent: Wednesday, August 25, 2010 10:36 PM
  Subject: Re: [GSBN] SB Overhangs (was Big News!)

  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

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  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:

    a.. Strawbale is not yet in the IGCC.  That's because it isn't finalized (and SB could even be entirely removed). 
    b.. 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. 
    c..   

   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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