Chad Sentman wrote:I feel like I know just enough to be dangerous and really mess something up through my ignorance, not knowing what I don't know.
This reflects a level of wisdom, that many are lacking...including some that are now trying to "reinvent wheels" and "teach others" what the "don't know" thoroughly enough to actually teach...
Chad Sentman wrote:I would find it really helpful if there was some sort of "recipe" book or "ingredient" list that I could refer to to know when you use which materials to build with to get the desired effect.
There are many, and some are hundreds (if not thousands) of years old. Unfortunately you must be an avid academic and have been plowing through these many tombs of text for a very long time (often in other languages) to glean any applicable information. Part of my own goals is to create such a "recipe book" if you will for others to employ or at least be able to "jump ahead" in understanding many of these natural and traditional building systems. If I may be so bold, please look and many of the conversations I have started here at Permies and I am sure you will get a great deal further along in your understanding. Many have links to other sites as well that can expand your familiarity with the building modalities.
Chad Sentman wrote:For example, "cob is made of clay, sand, and straw." Is this ALWAYS the case? It seems to me that I've heard that it can be made without straw.
This is such a broad subject that, as Bill has implied, would be difficult to address in just a single post as it could (has) filled entire series of books. This topic and its related elements is so vast and comes from so many different cultures over such a long period of time one is challenged to even know where to begin? Just doing basic "Google Search" in English on the following could keep one reading for days if not months...and that doesn't even begin to address the additional knowledge to be learned by travel and research in other languages...
Clay- Slip Clay Straw/Chip-Cob (Cobb-Clom)-Tabya-Adobe-Bousillage-Colombage-taipa-bajareque-木舞 (Komai = lath)-土壁 (Doheki=daub), 土塀 (Dobei=earth wall)
Chad Sentman wrote:I know that the function of straw is to add tensile strength, something like an internal net or web to hold it together. Under what circumstances would I NOT want this? When is a longer or shorter length of straw preferred? When is it preferred to substitute wool?
I am probably going to repeat this a bit, but these questions would take "chapters" (at best) to fully address and even then could be considered limited in scope. All forms of "clay architecture" has to have a "fiber" additive to the matrix to be functional, and I know of none in the "cob family" that doesn't. When we move into rammed earth, CEB (compressed earth block), poured earth, and a few related, these fibers may at times be omitted but that is not to say that this would render a stronger matrix...Fiber is always going to add resistance to bending and tensile strength...
Chad Sentman wrote:What function does the sand perform? I sometimes hear people talking about "sharp sand" but what other kinds are there, what is the differences between them, and when to use which?
Sand is a filler to start with, and then adds other physical properties like flexibility and compression strength to the matrix of the "cobb." Just as marbles or bearings would roll under your feet seldom do they have application in good (stout) cobb or mortar mixes. Round sands can and do have a role to play in "esthetic surface applications," and they maybe all that is available on some project...so...the architecture and the cobb application must be modified accordingly. This is one of the reasons I seldom (unless doing historical restorative and conservation work) ever recommend cobb that does not have a timber frame supporting it.
Chad Sentman wrote:I've heard reference to a building material with the perhaps unofficial name of "cobbish," which if I recall correctly is clay slip and perlite. When do I want to use this over regular cob?
Hmmm..."cobbish" is actually a generic term to any "cobb like" matrix and may have an extremely broad range of ingredients.
Chad Sentman wrote:Sometimes I feel like it's a case of learning about a more "traditional" method, and then learning about a more recent innovation that makes it better (and not knowing why), AND not knowing which method is which, the traditional or the innovation, so I end up with both sets of information in my head, not knowing them from another, and then they sort of fuse together over time, giving me a mix of jumbled information. Or sometimes, the YouTube videos I watch give me "bad" information because I don't recognize that the uploader is lower on the Wheaton Eco-Scale than I am.
This section of your query speaks to my often observed..."blind leading the blind" and/or "reinvention of the wheel," concepts that I too often see/read on the internet. It is, most of the time, a level of modern practitioners hubris and overall ignorance of a medium that takes them down the path of actually being able to "improve" on of these "traditional systems" of "natural building." It does happen sometime, yet I have never seen (or hear tell of it) coming from someone that doesn't have decades of experience
and knowledge about a vast array of traditional systems and a very mixed background of skill sets. Even then, it is usually just a "tooling change" in applying principles of modernity over what our forbears had...not an actual "improvement."
Many systems...like earth bags...may have there applicable use, but few actually doing it have a thorough history or experience in architecture and are more "romantically connected" to a concept than fully understanding whether it may (or may not) be the "best practice" for a given area or project
. Buckminster Fuller himself reflected this with the "geodesic dome" crase, that he himself finally acknowledge as having more pitfalls than originally thought.
For me, and those that taught me...it would seem a common rule of thumb...Don't try to "change a modality" until you have fully mastered and understand all the possible aspects of the modality, and be weary of "new concepts" with less than a century of experience and example behind it...
Chad Sentman wrote:For example, when learning about earthship houses, I see cases where someone has made a wall out of old glass bottles with some sort of cob or adobe in between. Why? Is this a cosmetic thing? Is it about letting light pass through into the house? Does the glass give some sort of structural or thermal benefit? Is this just an interesting way to take glass bottles out of the waste stream?
I've seen someone do something similar with a Rocket Mass Heater, building a wall of the thermal mass from row after row of aluminum cans as "bricks" with a sort of cob-looking mortar between them holding them together. What is the purpose of this?
Bottles in walls...90% aesthetic, 8% altnet function to the wall matrix itself, and 1% structurally similar to the overall matrix. That is the best generic reply I can give to the above as each case could be somewhat different...
Chad Sentman wrote:What I would find incredibly helpful is:
1. A list of commonly used natural building materials, including their purpose in the mix
2. A list of common recipes including rough proportions of each material in the first list
Material | Purpose (Thermal properties, structural properties, etc.)
Straw | Adds tensile strength, has good insulative value under these conditions, has good absorption properties under these other conditions, often used in these applications
Sand | ?
Perlite | ?
Clay | ?
Wool | ?
Brick | ?
Firebrick | ?
Durablanket | ?
Duraboard | ?
Lumber | ?
Cordwood | ?
Rock | ?
Bamboo | ?
That...simply put...is the book(s) that I hope to contribute my small part to and would take many hundreds of pages to even begin to address properly...Sorry, as I know that probably isn't as helpful as you would like...My partial reading list is here at Permies on several post, and may be of value...