Cob Code Project

10/21/96

COB CODE PROJECT UPDATE

Attached is a copy of COB CODE PROJECT which I wrote last December. This was presented to a meeting of the SFAIA codes committee at that time and it was received with what I have since come to realize is the normal mix of WOW, skepticism, and rejection. Nobody on that committe has bothered to call me back.

Also attached is a short article about why a cob code is needed. This is due to come out in the next issue of the CobWeb newsletter.

This spring I ran a booth representing Cob Cottage Co. at the Grand opening of Real Goods in Hopland, Ca. The publics reception of cob at that event was very enthusiastic with only a small percent of folks with looks off "what planet did you come from ?".

Also, during this past year I have been able to communicate with a few structural engineers and architects specializing in earth and/or natural building and have come up with the following thought extensions to cob building and the Cob Code Project paper:

David Murphy, a structural engineer working out of San Francisco on viewing Penny Livingston's project in Pt. Reyes was concerned with what he perceived to be a lack of shear capacity on the window filled South facing wall. This wall consists of two curved segments separated by a door and with narrow cob piers between the several window openings and the door. David's premise is that these narrow cob piers will not be strong enough to resist earthquake forces and thus create a "weak side" to the building which could lead to rotation and seismic failure. He recommended that all cob buildings in earthquake country be balanced and have a wood or concrete top bond beam to give rigidity to the top of the building.

Fred Webster, a structural engineer in Palo Alto, Ca., works with adobe and is involved currently in a project to write a rammed earth code for Sonoma County, Ca. Fred has written an article on "Adobe Codes" a copy of which is attached, Fred made these comments on the Cob Code Proposal: It's ambitious and covers more than required: The rupture test should be done from the side instead of downward - this is to keep the gravity load of the test sample mass from effecting a test result of less than the actual rupture strength: Testing should be done within an accepted ICBO format to assure that the pre-code testing results can be acceptable for ICBO review of the code proposal: Ouality control will be the big issue with building officials (this might be dealt with by having the code require a minimum material strength ). Fred estimates that an approximate material strength of 30 psi will be what is needed to meet Zone 4 seismic strength requirements (see Freds article for the seismic zone map of the USA).

Bob Bruce is a structural engineer in Emeryville, Ca., and is the editor of a report for the State of New Mexico about seismic issues regarding alternative building methods. Bob feels that some important issues regarding the seismic strength capacity of cob are: shear strength: post elastic behavior; a means of controlling cracking: using thick walls so they don't fall over when they crack from seismic forces and using mesh in the wall to keep it together, We discussed the use of straw and other possible fibers in the wall and Bob put forth the notion that the development length of the fibers is an important factor worth studying. That is to say that a fiber length in excess of a balance between the earth mixture's ability to grasp the embedded fibers and the actual tensile strength of the embedded fibers is not needed. If we can figure out how strong a given fiber material is and balance the fiber length to the earth's ability to grasp it, anything longer may not add to the strength of the wall. (This potential for using a shorter fiber length might prove worthwhile in a search for more efficent and or mechanical means of mixing cob). Bob suggested what he called the $1.98 test: making a series of small three inch cube samples of cob containing different possible fibers. These could be smashed with a hammer and would tell right away if some fibers are more promising than others. For the actual cob code testing procedure he suggested using an ASTM test protocol to assure acceptability of the test results. Bob estimates a material strength of appx. 10 psi may be what is needed to resist an eight Richter earthquake (Zone 4 maximum).

Miles Allen, a New Zealand architect working in earth building, had this to say, The cob buildings in New Zealand that have with stood earthquakes are those that are well built, well connected (continuity of structure), and well maintained, The foundation should serve to protect the wall from RISING ground moisture. The straw in the wall acts a fiber to assist with stiffness but not as a structural reinforcement. In fact, the straw, pine needles, tussock stems, etc provide irrigation channels to allow the water to leave the earth wall evenly thus reducing shrinkage and significant cracking. Miles is currently involved in a project to write three earth building codes to cover five forms of earth building. Correction for over drying sounds tricky, Determining exact percentages of soil constituents is not necessary "this isn't rocket science!". Reinforced earthwall panels six feet square by eight inches thick have been shear tested in New Zealand with excellent results, A possible construction method would be to tie a bond beam on top of the wall to the foundation with sleeved and tensioned Vertical rods in the wall at four feet on center. This would act to tie the roof diaphragm to the foundation. Shake table testing will be very expensive, it might be better to collect smaller bits of data from tension, shear and compression strength tests and extrapolate. An alternate to a shake table would be a simple swinging tilt table to simulate % of gravity lateral (sideways) loads. Relative testing of exterior wall finishes could be done With a simultaneous series of wall panels exposed similarly for a period of 10 to 15 years. An important cob variable is the moisture content: before mixing, at placement, and in service. Miles finishes to say that code writing is not for the faint hearted.

An aside is called for here to point out what is obvious from the above, to wit: These folks and others not mentioned are all experienced experts in earth construction and structural engineering and they at present do not agree about such critical issues such as required material strength and the need/function of straw (fibers) in the cob. This just further points out the need for a well designed test program to give solid information based on fact as to exactly what we can expect for cob and how it can best be used to construct buildings.

Recommended reading for those of us who really have our minds in the dirt: Earth Construction - A Comprehensive Guide, by Hugo Houben and Hubert Guillard, Intermediate Technology Publications, 103/105 Southhampton Row, London WC1B, UK. ISBN 1 85339 193 X. Can be ordered thru Builders Booksource in Berkeley, Ca.

On the funding side of things. I have gathered in preliminary info on a few foundations that may be interested in funding work towards a cob code. The next task will be to write inquiry letters for funding tailored to the goals of each foundation, If any of these are successful, then a full application with proposal will be needed. To be eligible for funding a non-profit fiscal sponsor needs to be found, To this end I have contacted a couple of possible umbrella organizations but as of yet have no commitments. This all takes time and energy, So far I have been working pretty much alone on this project. If you or anyone you know are interested in joining the pursuit of making cob accessible to the millions of people effected by building codes, then please contact me.

Thanks and cob on!

John Fordice

MAKING THE BUILDING CODE WORK FOR COB

The solution is obvious: CHANGE THE CODE!!!!

The best way to do this, to change the code and make it work for cob, is to create a new section for the cone which deals specifically with cob. This will allow building departments to use the code to recognize cob and deal with it on the basis of what it actually is. There is a process for amending the current code that is available to anyone. One simply submits a proposed code amendment to the ICBO. All such amendment proposals are reviewed in an annual process, and if the claims made or implied by the proposed code change can be substantiated, the amendment will be accepted, and will become a part of the next published code (new editions occur at approximately three-year intervals). The key to success is the ability of the proposal to survive the scrutiny of the review process.

To write a new cob section for the UBC, a program of basic research must be undertaken. Cob as a structural system needs to be subjected to a rigorous series of accurate tests which measure the nature, strength, and performance of cob as a building material and technique. A set of realistic cob construction standards with hard data to back them up can then be developed and used to form the basis of a reliable and believeable cob section for the UBC. The purpose of this testing will not be to negate any of the hard-won empirical knowledge about cob we now have, but rather to put measured truth to it. Nor will such testing deny the spirit and magic of cob. It will simply deal with the hard fact that when cob can be factually shown to withstand the various forces that affect buildings it can then be accepted into the building code.

For a cob testing program to be acceptable to code authorities it needs to be done within a sanctioned testing facility. Adequate funding is critical to making this happen. A relationship with a nonprofit organization interested in helping make a cob code happen needs to be established. sources of funding need to be found. I have drafted a PROPOSED COB TESTING PROGRAM as a beginning vehicle in the search for funding. Can you help to make this happen? Do you know of possible funding sources that would be interested in cob or sustainable natural building? Are you or do you know of a structural engineer or building official who is interested in earthen construction? Or do you know any other people who might be interested or want to help? If any of this speaks to you and you would like to become involved please contact:

COB CODE PROJECT
c/o John Fordice
1828 Fifth Street Berkeley, Ca. 94710,
(510) 549-1033 phone/fax

12/5/95

COB CODE PROJECT

ABSTRACT of:

PROPOSED COB TESTING PROGRAM

The following paper is a beginning draft proposal for a program of testing and code development for Cob Construction. The proposal starts with a brief introduction that speaks about some of the pressing environmental and political issues which face us both as members of an influential culture and as professionals involved in the creation of buildings.

The second part presents a short picture of cob as an enduring historic resource: a means of earthen construction that has shown an ability to withstand earthquakes; and a way of building which is reemerging into our present world of construction.

Part three discusses why a building code for cob is important. If Cob is to again become available as a building technique, a standardized code which is true to the actual nature of earthen construction will benefit all who wish to build with it.

Part four talks about how our present understanding of cob is for the most part based on empirical knowledge. A structure of proposed steps toward a cob code is put forth.

Part five is an outline of goals for a prescriptive cob construction code. This consists of a listing Of what currently seem to be the critical issues which both the cob builder and the building official will need to recognize. A short acknowledgment of the need for a Performance code is also included.

Part six is an outline of the main goals of the proposed program of cob testing. The intent of this goal structure is to the list the various types of information that will need to be gathered about cob in order to develop a realistic code.

Part seven is a description of the actual testing to be done. The various tests are intended to provide a clear and quantifiable picture of how cob can be expected to perform as a building material. A short description of each test is included along with the goals of each individual test, and now that test is intended to relate to the succeeding tests. The last part is a listing of the variables which can effect a cob construction project. This list is included last in this paper because it is long and perhaps daunting if one is not familiar with cob. It is long because I have attempted to be thorough and not miss anything. However it is worth stressing that cob is really a very simple and easy way to build, and once someone gets their hands in the mud, most of these variables become self evident. Cob is very flexible and an exciting sense of discovery can be found in working with this wonderful sticky material.

COB ON!

COB CODE PROJECT PROPOSED COB TESTING PROGRAM (a working document)

1. Introduction
2. What is Cob
3. Why a Cob Code
4. How to create a Cob Code
5. Goals of a Cob Code
6. Cob Test Goals
7. A Proposed Cob Testing Program
8. List of Cob Construction Variables

I. INTRODUCTION

However, in adversity lies the seed of creativity.

What can be done to turn this situation around? one set of solutions can be found in the promotion and use of earth as a building material, Earth is a building material that is literally under our feet. It is everywhere, inexpensive, durable, and easy to use. Earthen construction has existed for millenia. Indigenous peoples world wide have developed locally intelligent methods of building with the earth. Earth has withstood the test of time as a means of fulfilling our common need for shelter. Earth as a building material and technique has many wonderful attributes. It only needs to be explored, used, and set free, In earthen construction can be found solution to some very serious problems.

Cob construction is one such way of BUILDING WITH THE EARTH.

II. WHAT IS COB

Currently in North America, Cob is experiencing renewed interest This is as a result of a series of workshops on Cob Construction which have been conducted over the past few years by the Cob Cottage Company of Cottage Grove, Oregon. In August of 1995 I attended a workshop they held in Point Reyes, California. During this workshop a group of 20 people came together for one week to construct a small Cob building. This was a seminal experience for me and I came away from the workshop with a desire to help bring Cob into our world of construction here in California. For me this has taken the form of introducing Cob into the Uniform Building Code.

III. WHY A COB CODE IS NEEDED

The UBC covers most building methods commonly in current use. The list of included materials and methods does not include any Earthen Construction other than Adobe and this in only a very brief and limited manner. The UBC makes no mention at all of COB as a recognized means of building.

The UBC does allow for the use of "Alternate Materials and Methods of Construction". This is done on the basis of a by case" approval by the local building official. This results in the Alternate Material being judged for its construction suitability on the basis of what is written in the CURRENT UBC. An example of how this has been misused in actual practice is situation where RAMMED EARTH construction has been required to conform to Chapter 24 (masonry) of the UBC. Rammed Earth is not masonry, and to treat it as such is to do a disservice to both Rammed Earth and the UBC. Such a shoe horn approach, while understandable given that no appropriate earthen building standards exist, is faulted at best and could potentially be harmful.

What is needed is a REALISTIC CODE for each form of Earthen Construction, including: Adobe, Rammed Earth, Cob and any other method with which people desire to build. Anything less is not an optimum solution for building with earth in a SAFE, RESPONSIBLE, and REALISTIC MANNER.

IV. HOW TO CREATE A COB CODE

Cob as a MATERIAL and a TECHNIQUE consists of the combination of a series of variables which when properly combined will result in a sound structure. Each of these variables needs to be identified and tested in a series of combined relationships with all the other variables. The GOALS of these tests also need to be identified. once the variables of: material, technique. and goal have been established it will be possible to design a TEST SERIES which will result in valid COB PERFORMANCE data. This data can then be used to develop a reliable Cob Code. The CODE DEVELOPMENT will also require identifying and establishing a set of goals about exactly what the Code is intended to do. This will all most likely not occur as a strictly sequential set of actions and will undoubtedly require including progressive feedback as the TESTING PROGRAM progresses.

V. GOALS OF A COB CODE