[GSBN] SB wall height limit (was Clay plaster language for IBC)

Thu Jan 26 01:10:20 UTC 2012

Thanks Derek,

Delayed reply on this.  I was aware of this problem, which we addressed
during a meeting of our ³structural task force² Sunday.  The proposed ratio
will be increased to 7:1 or 8:1 ³of stacked bale height to bale width
between restraints².  If an 8:1 ratio is proposed there will probably be a
height limit of 12 feet.  Taller walls could be built, but they would need
intermediate restraint or would need to show an engineered design
demonstrating they adequately resist buckling (under any imposed vertical
load or design out-of-plane horizontal loads).

This height to width limit is for walls with mesh reinforced plasters or
external or internal pinning, or out-of-plane restraint by structural
framing (with sufficient attachment).  The height to width limit for walls
without any of those means of resisting out-of-plane loads will be lower
(still being determined).

The historical height to width limit for load-bearing walls has been 5.6 to
1 (going back to the 1995 Arizona code written by Matts and David
Eisenberg).  For 3-string bales laid flat this is 10¹-8² (8 courses).  For
2-string laid flat it is 8¹-4² (7 courses).  2-string laid flat doesn¹t
really pencil out, at 6¹-6² or 4.25 courses.

I anticipate flak during the review process of anything over 5.6 to 1.  I
already heard it during the IGCC process, even at 6:1.  Kevin Donahue
(structural engineer in CA) is writing a rational analysis to defend the
increase based on out-of-plane testing and fundamental structural mechanics.

Another point of reference by the way, is that in the IBC, unreinforced
adobe has a height to width limit of 10:1 (with a minimum exterior wall
thickness of 10²).

I may be saying too much here and it¹s a little more complex than what I
describe, but I hope this answer is sufficient.

Martin

On 1/18/12 9:12 AM, "Derek Roff" <derek at unm.edu> wrote:

> Hi, Martin,
> 
> I appreciate your continued work on so many levels for the promotion and
> support of more sustainable building practices, procedures, and modalities.
> I'd like to ask again, about an element of the proposed code, which seems to
> contradict some of the goals that we share on this list.  Will your next code
> proposal continue to effectively ban stacking bales on edge, or using
> smaller-dimension bales, such as those you used in Pakistan and Haiti?  The
> provision that I am referring to limits the height of a wall to six times its
> thickness.  This means a maximum ceiling height of 6', if one is using the
> 12"x12" bales like you used in Haiti, and 7', if you stack the common American
> two-string bales on edge.  Such low ceilings are likely to violate other code
> requirements, and few of us want to be forced to build a portion of our wall
> height out of another material.  These building options are used on some
> projects by many of our most experienced and innovative builders.  The
> structural strength taller walls is documented in multiple university tests on
> several continents, and its reliability in practice is shown in many of the
> oldest historical strawbale buildings.  I would be very sad if a forthcoming
> code contains a provision that makes these building options illegal.
> 
> I think we would all like any code proposals to be a good as possible, and of
> course there will be differences of opinion on just what "good" means on
> certain points.  However, to support a code provision that bans a widespread
> strawbale building option is something that I feel requires extensive
> discussion.  I'm hoping that the provision has been removed from the code
> proposal, but if it remains, are you willing to discuss it?
> 
> Thanks,
> Derelict
> 
> Derek Roff
> derek at unm.edu
> 
> 
> On Jan 17, 2012, at 1:10 AM, martin hammer wrote:
> 
>> Clay plaster language for IBC
>> Hello all,
>> 
>> I proposed a Strawbale Construction section for the International Building
>> Code (IBC) on January 3.  I have been allowed by the International Code
>> Council to make adjustments until January 25, before the proposal becomes
>> public.  
>> 
>> I have continued refining the language with a structural task force (that has
>> worked on this since October) as well as obtaining input from the Structural
>> Engineers Association of California, a long time opponent strawbale
>> construction in building codes.  They are now pulling on the same end of the
>> rope.  Dan Smith and John Swearingen of this list have helped adjust the
>> non-structural language.  I also received input from Andy Mueller of this
>> list for a renewed Northeastern US perspective.
>> 
>> One area of this ³code² I feel is under-developed is the part on Clay Plaster
>> (and secondarily Soil-Cement).  An entire section is devoted to ³Finishes²,
>> which is mostly about plasters.  This includes clay, soil-cement, lime,
>> cement-lime, cement, and gypsum plasters.  For the last four plaster types I
>> reference long-standing sections of the International Building Code or ASTM
>> Standards (with a some adjustments for use of these plasters on strawbale
>> walls).  Wherever possible (and wherever not inappropriate for strawbale) it
>> is best for this proposed strawbale section to be in sync with the IBC and
>> its referenced standards.
>> 
>> However clay plaster (and soil-cement plaster) is new territory for the IBC.
>> New language must be forged here, but it needs to be code-appropriate as
>> follows:
>> 
>> * Minimum practice, not best practice.
>> * Enforceable 
>> * Says what shall be or shall not be done, not what should or may be done.
>> 
>> Would anyone from this list (with good clay plaster experience) like to be
>> part of a mini task force on this issue?  If people let me know by end of
>> Wednesday January 18, the individual or small group (no more than 3?) would
>> have through Monday January 23 to propose language.  I could send you what I
>> have currently off-list or you could choose to be blind to it.  Looking at
>> existing language regarding plasters in the IBC or in ASTM standards (if you
>> have access to these), is not mandatory but might be useful.
>> 
>> Is anyone willing and able?
>> 
>> Thanks.
>> 
>> Martin Hammer
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> 
> 
> 
> 
> 
> 
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