Rammed earth vs. compressed earth blocks

I have a quick question. I have been reading about both of these building methods and I find it difficult to separate them. It seems that rammed earth is very similar to compressed earth blocks with the exception that the rammed earth "block" is the size of the whole wall...is that correct?

Pretty much.

Yep. They are very similar, however, made very differently:
https://www.youtube.com/watch?v=9OU5ulNgiqo

Here is a video that explains a bit better: http://opensourceecology.org/portfolio/ceb-press/

Also another online resource for more information on building with earth:
Hand book for Building Earth Homes:Hand Book for Building Earth Homes

Nate at http://returntotheforest.org/

here is a video that gets the "rammed earth wall" point across.



seems that rammed earth walls lend themselves to a bot more mechanization (skid steer and tamper), but with rammed earth bricks you dont need a bunch of heavy machinery.

As the above posters said, the outcome (the wall you build) is the same. The route to get there is completely different.

I built a block press, because one of the more important considerations for me was this:
You can make blocks here and there (both "here and there" in terms of space, and "here and there" in terms of time), and assemble them into a wall when you're ready. Making a rammed-earth wall, you can only do it when and where you're ready to have a wall.

There are lots of other reasons you might prefer one method over the other, but that's a big deal to me.

Correct me if I wrong but blocks do not have to be sized for an "entire wall". They can be a size that can be off-site built like CMU's are then shipped to the site to be assembled with a mortar. Rammed earth is site build in form work for larger sections, so more monolithic. There can be large differences in load carrying capability of mono-structure depending on size. The labor hours and embodied energy between the two can also be large depending on shipping cost and assemble time.

also, brick can thermally bridge unless you lay several wykes, re does better with an insulated core.

Compressed earth blocks are used for masonry construction. Rammed earth walls are monolithic.

That is a massive difference in mechanical characteristics. You do not achieve the same thing by two different paths.

Which is appropriate to a given situation depends on more variables than I understand

Both can be done on site with very low tech and minimal energy costs, if you want to go that way. Both can also be done with lots of mechanization and energy costs more along the lines of cement works.

Peter Ellis wrote:Compressed earth blocks are used for masonry construction. Rammed earth walls are monolithic.

That is a massive difference in mechanical characteristics. You do not achieve the same thing by two different paths.

This is true. Being in Michigan, I forget that in lots of parts of the world, seismic stability is a high priority.

Here, the highest priority is probably heating, so an earth wall comprised of units and a monolithic earth wall don't really differ. They'll behave very nearly the same regarding heat.

But seismic concerns, good point!

Scroll down on this blog about 2/3 the way and look @ the 'snap shot of thermal mass' graph of a 3 wyke (row) mass brick design with thermo-couples on the interior and exterior surfaces of the wykes, in the Atlanta, GA area for a year, cold winters very hot and humid summers. You can see the inner and outer mass cycles in a 6 hr lag time with respect to one another due to the temperature differences each sees and there are no thermal bridges due to the isolation of the 3 rows of brick. Since the two outer rows isolated the inner with air, the inner is allowed to store conditioned air from inside HVAC and/or solar passive and release it in a 6hr (towards cold evenings) lag without seeing a thermal gradient or input from the exterior. An insulative core would do the same thing and provide strength if sandwich bonded. The utility bills are low. Soil and concrete have around the same heat capacity and thermal conductance. If this were one row of brick it would bridge influencing the function of the thermal mass interior.

http://hopeforarchitecture.com/blog/


RE has a high aspect ratio (width-to height) some 24" thick walls. Since thermal conductance is a function of thickness it will not bridge as much, the inner heat will cycle at some surface depth with respect to outer surface temp and depending on the temperature difference across the wall will not bridge as easy. If you put a ductile core such as foam or bales in the center it will isolate the inner skin from the outer. The core along with the higher aspect ratio that prevents buckling from lateral loads would act as a shock absorber for seismic. This is why bale walls with mortar skins do well in seismic. Here is a shake table test where netting was used on the skins to improve tensile strength. Monolithic insulated RE or bale walls will transfer lateral loads much better than small bricks bonded together, RE and brick would perform equally structurally and thermally if the aspect ratio is the same.

I grew up in earthquake land close to an all brick town called Whittier, CA that crumbled to ground back in 90's. RE or block alone modulus of elasticity and stiffness is to high to do well in seismic lateral loading, better with a ductile core to take shock loads away from the skins, but the skins have to flex to as in clay vs cement and/or have netted skins that take tensile loads from the walls bending or bowing.

http://nees.unr.edu/projects/straw-house

My new design uses SIRE columns butted to bales, it will do well in any climate zone or lateral loading.

Hello All,

Per Tom's original question...


Mike Cantrell's

Mike Cantrell wrote:the outcome (the wall you build) is the same. The route to get there is completely different.

This is a good general synopsis of the process and outcome in this architectural modality.

, seldom do you (if ever?) ship CEB as compared to CMU, it is neither logical of logistical[fiscal applicable...it is the machine that is shipped. The two are not comparable at all. The only real similarities you could apply to both perhaps is they are "masonry units," of a form. CEB grew out of several adobe block and cinva ram industries. In the Southwest (where I used the machines first in the mid 80's, they formed adobe block. Then in the Middle East, India and Asia, the system for on-sight manufacture of CEB expanded over the decades, with many different forms and types of blocks. Some types are for dry lay with a lime plaster render and others are "joint lock" types that assemble rapidly.

Both too, can achieve (depending on design parameters) the same compressive load capacities, tectonic resistance capabilities, and thermal performance achievements. What limiting factors exists for both methods are only a characteristic of the design modality not the medium, or interstitial properties. Once the wall or other "diaphragm unit" is complete, they are considered (depending again on design) "monolithic" in nature. The "mechanical characteristics" can be virtually the same or very different depending on the system employed, yet again, this is more an aspect of design with the two systems, then the fundamental material matrix. Having been involved in several builds and designs using these systems, and knowledge of them for the past 30 years, I would describe both as very "labor intensive" and/or technical in general nature. If the goal is an enduring form of architecture and not a temporary structure, considerable effort of technology and/or labor must be employed to facilitate rapid (and uniform) production and progress.

Since technical, labor power, and design can be subjective in a given economic state...these variabilities are flexible.

Jay C: You use terminology I normally do not but I think or hope we agree that given the same material mechanical and thermal properties (in this can a similar earth mix) the manufacturing and assemble method will not change the material properties or what I will refer to as the “allowed” mechanical properties (compression, tensile, shear, bearing, fatigue) as derived by coupon testing or stress strain gages. Once you place those properties in a design, that design can either subject the material properties to loads it can operate in (called “limit loads”) or you can put the materials in a load condition that will exceed the material allowable (called ultimate load)….Creep load (where deformation begins to fail) happens prior to “ultimate load” , or cracks begin.

An example earth allowed loading:

Compression: 3,000 psf
Tensile: 2,000 psf
Shear: 2500 psf


The design can not exceed those allowables. If the wall or roof or what ever subjects the material mix to bending from seismic for example, the allowables limit load can not be exceeded. The cross section properties will determine the loading. Again, aspect ratio determines load distribution uniformity. Cement improves the material allowables and ability to react loads, it also improves adhesive mortar bonding strength or lap tensile/shear property.


A “monolithic” load path has a much better chance of operating in “limit loads” material properties. The stress/strain is reduced. Bonds are limited by “lap shear” and “lap tensile” strengths of the adhesive and are a functions of voids, that are less than the material(block) allowables. High temp and pressure bond lines and adhesives do better but will never be as strong as a monolithic design of the same materials. Locking blocks may be better to take out lateral(side) loads by 'locking' the shear plane from side loads (wind, seismic, etc) but not compression due to the broken interface and non-monolythic bearing area. There would more to consider there than “compressive” stress in a building, there is more to consider than compression as I noted in mechanical properties above in a nodal analysis of a complete building design. There is another set of many thermal properties to consider as well, not only thermally but there affect on the strength of material properties and the whole building design. Thermal fatigue or cycling for one example, can knock down the mechanical properties such as compression and cause buckling and cracking. The graph and test results I posted show that there is a large difference between designs that depend on mass.

Is there an earth build method that is not labor intensive? Most of what I have seen is labor intensive but the materials cost is dirt cheap! If you handle the labor properly I believe you can come out ahead of purchasing less labor intensive materials at the big box stores. One thing good about blocks is if you wanted to get out of weather you can make them in your warehouse, RE is site built although I saw some make some big sections in their warehouse and site ship them locally.

I am writing really fast today as my plate is full...sorry if my last post sounded "too blunt." You just added some great info to the post (probably more technical than many could understand...but really should if building with these earth systems! So a big thank you for adding that to the conversation!)

Cement improves the material allowable and ability to react loads,

Subjective on application...and there are other factors to consider. It is a common practice...but not ultimately necessary in the design...especially if a "natural build" is part of the ultimate goal. OPC has a huge carbon foot print, and is not environmentally sustainable. Some of the "rediscovers" being made in geopolymers have strong promise in CEB work and other "rammed earth applications."

A “monolithic” load path has a much better chance of operating in “limit loads” material properties.

Again, dependent of design modalities...both CEB and entire wall diaphragm rammed earth application can be considered "monolithic" in nature, form and function.

Is there an earth build method that is not labor intensive?

That is subjective...in my 35 plus years of facilitating and studying natural and traditional design systems, as I said before, I don't find most "earth builds," either easy, cost effective comparably, or low in required "human labor." Few of the builders - architects that I have worked with would recommend these modalities in most applications. There are some that specialize in this design system, and of course, recommend it highly...again...very subjective perspective on their part, as this is how they make a living. Clients hire me as a consultant often to give them the "big picture," and/or "outside the box" perspective on these different natural and traditional systems.

Most of what I have seen is labor intensive but the materials cost is dirt cheap!

Yes...if you do not have to augment the earth matrix with additional additives like geopolymer formulas or OPC (which I do not support for "Permies" design builds.)

If you handle the labor properly I believe you can come out ahead of purchasing less labor intensive materials at the big box stores.

Facilitate several of these yourself, and/or work in several different comparable systems for a few years, then tell me if you still feel the same way. Some do. Very, very few professional design/builders agree and challenge this perspective on the same issues as I have thus far shared. I would point out that the "big box store," does not enter the equation for me as a natural-traditional designer and builder...so that aspect I will leave alone as I don't support that type of construction either.

One thing good about blocks is if you wanted to get out of weather you can make them in your warehouse, RE is site built although I saw some make some big sections in their warehouse and site ship them locally.

Of these systems...I love this one for this and many other points. CEB has much stronger merit (IMO) than does general rammed earth. It is all relative to the given environment-normative culture and applied system(s). If it wasn't applicable (rammed earth) the Chinese would not have been building with this system in some fashion for the last 4000 or more years.

Thanks for your comments,

j

I've built with Adobe, Compressed Earth Block, and Cob. Admittedly I have no experience with rammed earth building. From my experience, here are a couple of fundamental differences to consider:

1) For earth blocks, you need a press. If you want to build with block, but acquiring a press is impractical for you, traditional adobe can be a reasonable alternative. If using a hand operated press you'll need a crew of at least six hearty individuals to mix soil, operate the press, move and stack blocks, etc. BTW, pulling the lever on a hand press all day long is also one hell of a workout! Rammed earth or cob can be achieved with as few as one or two people.

2) Any building done in place, such a rammed earth or cob, will be more efficient from the standpoint of not having to stack, and move blocks. When you consider moving hundreds or even thousands of 25-40 pound blocks to from the press to and from the drying field, the total extra energy expended can be significant!

Hope this helps!

Well since we are posting resumes out here, I have designed assemblies with many detail parts bonded to one another, in the past decade of 30 years as a PE and architect consolidating those designs to a monolithic. Most Architects are not PEs or understand loads, stress analysis, or thermodynamics. In just about every case cost drops from less assemble time and detail parts, betters load paths as seen in controlled hot box testing and field test results in less weight and dead loads. Loads are loads, stress is stress, there are no modality that will transfer structural loads better than a mono period, BIG difference there. It is VERY clear to me monolithic (and what I mean by that is NO bond lines wins), although I would entertain a test report showing otherwise?

I am in opposition to OPC too, I am just not sure what else has the same properties?

I am opposed to big box construction too, working hard to get our restoration company out of those stores but, it is not always easy becoming the manufacturer of local resources, for example, when wood is not abundant locally, and there are no saw millers around, driving my embodied energy and cost to eating my profits away. I can only on-site manufacture so much to hold a reasonable schedule that cost in days on market, loans, etc. I have to be reasonable and bring bread and butter home as a builder. I refer to the big box stores since that is where all my competition goes, soon I hope to still be competitive and not rely on them.

I have no building experience with any of the natural methods, although I am planning on doing some test sampling soon. Knowing what I do, I will focus on monolithic SIRE (structural insulated rammed earth) not becoming a brick manufacturer or competing with that industry. I think I will be more competitive to concrete form workers. Is there a pour form of earth building similar to poring concrete in forms that takes the labor hours down?

I like the idea of my business only having to rely on a couple of laborers vs 6, we have issues scheduling reliable labor that is hard to find, managing material delivers, quality of big box construction….they add to cost one way or another. The less I have to rely of labor and factories the better.

Hello Daniel G,

I apologize ahead of time as I don't have time to rethink this response (I know it sounds a bit challenging )

1) For earth blocks, you need a press. If you want to build with block, but acquiring a press is impractical for you, traditional adobe can be a reasonable alternative. If using a hand operated press you'll need a crew of at least six hearty individuals to mix soil, operate the press, move and stack blocks, etc. BTW, pulling the lever on a hand press all day long is also one hell of a workout! Rammed earth or cob can be achieved with as few as one or two people.

Very subjective perspective based on multiply factors. All can be achieve "solo," and have been for millenia. As this was often the case in rural settings for all these systems. Of course some are more dependent of "machines" and a rammed earth press form is probably the easiest of machines in this family of machines to build as it is very similar to the different molds used in making adobe block. All benefit greatly from have a strong back (and several of them...)

2) Any building done in place, such a rammed earth or cob, will be more efficient from the standpoint of not having to stack, and move blocks. When you consider moving hundreds or even thousands of 25-40 pound blocks to from the press to and from the drying field, the total extra energy expended can be significant!

In the macro perspective (or in general) this is probably a true statement in most applications...perhaps However, if all aspects of logistic, design, application, rendition, and multiply other factors are considered...this may not be the case and each will...in the end...be very similar in final fiscal and physical outlay accordingly in there give economy of implementation. Again I stress to clients that unless a "earth form" of architecture is not within the vernacular for a region...it most likely is not the wisest form to chose, nor the most economical.

Again, sorry if this reads as a wee bit challenging. I try not too, yet when we share views here, it is important to those "learning" that "subjective views" be examined from multiple facets, objectives, and perspectives.

Regards,

j

Thanks for the apple Jay, I was wondering what those were for I sit around 100 engineers right now, a high tech factory below me, and a muti-million dollar lab next to me with test Engineers in it. Rarely in the design phase do Engineers agree on things. We have a place to sign drawing's called "The war room" lol, imagine that . I got to love the lab guys, as big headed know it all some think we are, the test results are were all bull comes to end. We don't debate with the test guys or their results, well unless someone wants to challenge the set up.

Lots of opinions on the internet amoung the "Building Science" community by some that obviously are not Engineers, I can tell by post one. Basic static and dynamic stress analysis that has been proven for years is not subjective or up for debate. In this case compression force reaction being pressure per area, if area is reduced or ineffective by stacking or bonding blocks or legos compared to a mono design there is nothing that is going to change that fact.

Anyway, good to be here.

I am in opposition to OPC too, I am just not sure what else has the same properties?

Though they are trickier to work with, pazzolans and lime stabilization. Adobe (clay) is also a stabilizer.

I am hoping for industrial hemp to be grown in the US again (and it is already starting up in Colorado). Hemp hurds mixed into a hydraulic lime slurry makes "hempcrete", which is much better than OPC from a CO2 perspective. Hempcrete requires no rebar, is flexible (much better seismic tolerance), and has a higher R-value. Poured hempcrete floors are actually comfortable to walk on. It's easy to make walls, too, with a slip-form.

As a traditional historical Timberwright (among other worn out hats) I have worked with many Architects and PE over the years (my personal PE, Ben of Firetower Engineering Inc. and I have worked together for over 35...and still counting... ) Your comments and observation about the "war-room" is sooooo true...you just got to love it or you will be driven made...

I just actually helped (saved according to them) a client from a huge "architectural bill." They called me in as a consultant (and future designer for their project) when the preliminary drawings...well...just did not get them excited and the $6K bill given them by the Architect really "soured" it all for them. The firm was rather pushy (too pushy?) and basically made too many demands and had a really condescending tone toward these fine folks. The final meeting (in a war room) was not a pleasant one. I brought my own CAD concept and drawings, client liked my "rough" concept better than the firms, and since I was the Timberwright on the project thought I should be present for further discussion. The architecture firm did not want to see the project as a timber frame but instead use their own contractor and "stress skin" the project, with faux beam work and cement or vinyl siding...icky!!! Before we even got too deep into the meeting I just asked a few simple questions...for the $10,000 of thousands in design fees these client are going to spend with you (the architectural firm) what are they getting?

Their response was even more arrogant than I thought it would be...the Lead architect for the project simply said that, "well, there really isn't any comparison to be made....you are an amiture, not an architect, and not licenced as an Architect so can't do the work we do for these or any other client...nor prepare professional drawings for approval to do this project..."

I almost laughed out loud...but instead looked at the clients and asked if I could ask one more question. Which was, "if you do these drawings for OUR client do they still have to get PE approval? Which of course was a resounding, YES, and of course, "They worked with the best in the industry..."

I simply stood, before excusing myself from the meeting, and said to the clients the choice was theirs, follow this firm's lead on the project or chose to work with me, my team of Artisan, and our own PE who is part of the "TEAM," and we will try and facilitate the home you wish to have...with a much much lower design fee for the project...

wrote:Loads are loads, stress is stress, there are no modality that will transfer structural loads better than a mono period, BIG difference there.

I am sure you are just talking about in the comparison of "mass matrix" foundation and wall diaphragms...as timber frames transfer tectonic loads extremely well (probably better) than do any masonry or mass architecture. Are we on the same page there?

wrote: It is VERY clear to me monolithic (and what I mean by that is NO bond lines wins), although I would entertain a test report showing otherwise?

Yes...in general we are in complete agreement there...kinda, yet...there are...Oh No...here we go...strang vernacular examples like....


Opus Craticium

Taq Construction

Dhajji Dewari Construction

Koti Banal Construction

Peruvian quincha construction

bahareque or taquezal construction

Hımış construction

Colombage Construction

All of which take us into directions that 90 % of the folks I work with (Architect and PE included...) don't think about and/or have never considered or heard of....

wrote:I am in opposition to OPC too, I am just not sure what else has the same properties?

I am so very glad you don't like OPC too...you don't know how happy that makes me...and the above examples are just the tip of the iceberg when it comes to more germane vernacular forms that all too often surpass modern concepts in design, yet they are natural, sustainable, and last in some cases for millenia...well beyond the current trends in domestic architecture of only a few decades...

, I hear you about the challenges of staying competitive...we should talk soon offline on that one...We are not only fighting a battle with the "industrial complex" itself...but also the normative culture of a consumer society. Take heart brother...it can be done, and your thinking is great and you are heading on the proper bearing...As I tell my clients..."look to the vernacular" for a region or biome, and in most cases that will tell you what will endure the best, and often the least expensive in the macro view.

If you are a "die hard" SIRE man (I am friends with several) bless you for the work you do. Many are not the best choice for a given area...but if the client can afford it, and they have a dedicated design team behind it...this "modern" form of an ancient modality in mass wall earth design is virtually "fool proof"....(and bomb proof.) SIRE is an awesome design approach in many ways...and anyone with the bank account to afford one, and enjoys the architectural affect, and how they present on their building site, will be rewarded with a home that is priceless (and will last generations, of that I am sure.)

Warm Regards to all reading my rambles,

j

Jay, interesting dialog. Sounds like some big headed Engineers at work. I see it all the time, the same ones that don not respect the knowledge of the builders that put their designs together. I’m humble enough and smart enough to seek out their knowledge to make sure my designs can be built, and the client is satisfied. Although I did read yesterday of a client that was not satisfied with material choices for two years. I plan on talking to my attorney about my contracts to make sure that does not happen and there is a clean way out.

I have seen some heated battles in war rooms across America. In this case not one PE or Designer (Architect) is signing the drawings. We have many Engineers such as Materials and Processes (M&P), Manufacturing, Test, Stress. Design Engineers the center of it all are ALWAYS happy to the get the Stress Engineers that the loads are satisfied. If he refuses to sign we strap him to a chair and call his manager, lol!

I have a seal right now that is leaking, I was sitting in a telecom last week listening to 6 different opinions as to why trying my hardest to stay awake. Most of the opinions from college grads trying to impress the program manager. Then the Stress Engineer showed a Finite Element Model (FEM) what would happen if a side or lateral load that was too large would cause. All the opinions did not match the model. I finally woke up and told everyone we need to focus on the model not meeting’s like this. So the Engineer that designed it is set on proving it right, now we changed the test fixture to take the load down and meet spec minimum, sort of like meeting code minimum. Test fixture will be done today, we go back on test with four more units. I am going to laugh hard if they fail since I think the design is bad. If it passes I will swallow my pride. Even if it passes, it will not sustain the field long IMO. There is a lot of history that says it will to spec, but when we change something, even the smallest aspect, history begins. This is how industry specs manufactures that twist things around to pass them. I see it first hand and I’m here to tell ya do not trust the factories. I’m referring to specs such as ATSM, ASHRA, ISO.

“am sure you are just talking about in the comparison of "mass matrix" foundation and wall diaphragms...as timber frames transfer tectonic loads extremely well (probably better) than do any masonry or mass architecture. Are we on the same page there? “

Tectonic? Had to look that one up.... You’re getting outside my vocabulary now, lol! I’m not knowledgeable to make the comparison to wood and earth mechanical and thermal properties, but I am learning.

I do know wood would never be approved today as a robust building materials. Wood is entirely unpredictable, if someone invented it today it never be approved as a building material. It’s strength properties depend on its orientation, no two pieces are alike, cruelly of all it expands and contracts based on relative humidity, it expands differently based on orientation, when in shrinks it expands, it shrinks and expands along the grain differently than perpendicular, shrinks and expands more at a right angle to the grain than along the grain, studs get shorter or longer, do not get thinner or thicker. It burns, rots, it can’t get worse but, after years of testing and use we understand it. That s why this industry designs with such high safety margins that fight themselves in weight and dead loads. There are far better material choices, better strength-to-weight ratios, and combinations that work well together.

“All of which take us into directions that 90 % of the folks I work with (Architect and PE included... ) don't think about and/or have never considered or heard of....”

And there is probably a good reason for that we know better. I am not sure if anyone has followed these designs that have 'lasted for centuries'” to capture all the maintenance required. We westerners have, we understand that structure is only as good as its weakest link. We are so good it we can design to failure, we know where the crack will begin and where it will end where I work. We know what happens when you load a beam with a point load it cannot take, for example rock point loaded in compression to a wood beam. We know most structure fails from bending moments, point loads from hard point fastening, etc...We know that well distributed load on a beam reacts much better. So although it is good to look at history and what some see as unorthodox building methods, it is a well known fact by many similar designs that have failed what geometry and material properties work well together. We also know what code allows and what PE's will sign. To be honest of the three industries I am familiar with auto, aircraft, and construction, from what I have seen construction has the least understanding and is the furthest behind in technology. That is why I am about ready to stop working in the other two. Help put this generation on a better more natural building track but, at the same time improve the technology and make some $ while I’m at it. I' old school too but very open to new technology existing today I helped develop. Composite are great since you can combine properties, you just have to be careful to not combine the wrong properties.

Yeah I'll PM soon so we can chat sometime.

Kevin EarthSoul wrote:

Terry Lee wrote:
I am in opposition to OPC too, I am just not sure what else has the same properties?

Though they are trickier to work with, pazzolans and lime stabilization. Adobe (clay) is also a stabilizer.

I am hoping for industrial hemp to be grown in the US again (and it is already starting up in Colorado). Hemp hurds mixed into a hydraulic lime slurry makes "hempcrete", which is much better than OPC from a CO2 perspective. Hempcrete requires no rebar, is flexible (much better seismic tolerance), and has a higher R-value. Poured hempcrete floors are actually comfortable to walk on. It's easy to make walls, too, with a slip-form.

kevin, just a quick note...thanks! I heard of SIRE chemist using pazzolans a while ago. Never heard of hemp. I do some internet looking for mechanical and thermal properties see what the real differences are and try and state them....I'll be looking for coupon testing we get code approval on and availability(does no good if costly to make available) if you know where I can find that into please inform. It is on my list of things to do, thanks!

By the way peeps our lab does extensive testing on fungi, got questions let me know soon because I'll probably quit soon.

Eve'n , et al,

I do agree with not ever blindly following "the word" of "factory specifications," on anything. Then again I am not a big fan of industry or what grew out of the IR (Industrial Revolution) in many regards, as it was more about "profit and consumerism," than practical thinking and application of known methods.

I don't mean to always use word like tectonic, "wall-roof diaphragm, etc... yet working with the PE in my circle of acquaintance, these are common terms. Tectonics (wind or seismic) are very common design criteria and of note on many frames I am part of.

I do know wood would never be approved today as a robust building materials. Wood is entirely unpredictable, if someone invented it today it never be approved as a building material.

You may have to explain how you mean that...Wood is "approved" all the time as a building material, both for industrial and residential application, even in civil projects as well, and that is on a global scale. Wood today is even (once again) being specified over steel and concrete in many of these applications from all wood timber "high rise structures" (soon to be built skyscrapers) to massive shopping centers, bridges, etc. That doesn't even begin to address the huge explosion in timber framing or the other "biggie" today...bamboo. Wood, is and has been a huge part of the building culture of humans (very successfully) for millenia, and once again is taking center stage on many projects.

As for "predictability" well that depends on whether you work extensively with it or not I would think. I, and those like me find it very "predictable" and if it wasn't, I wouldn't be able to have frames approved for construction...very often over steel and concrete, for both cost reasons and environmental sustainability concerns. Cellulose...in all its many permutations is a very common and ever expanding building material...not only in structural applications..but others as well.

As for your points on strength properties, orientation bearing considerations and expansion-contraction ratios, they too are very known and measurable (more so in some species than others.) I do believe you really need to be much more intimate with this medium to fully assess its qualities.

....it shrinks and expands along the grain differently than perpendicular, shrinks and expands more at a right angle to the grain than along the grain, studs get shorter or longer, do not get thinner or thicker...

This one I just had to single out. The rest of your points are vary degrees of subjective...this one is just not factual. Post (or studs) do not expand and contract with tangential deformation in most species of wood, and is very predictable in most cases. In compression wood is (by weight) one of the strongest natural materials there is in compression to the rest...

It does not burn, in many applications, the way many lay folk (and the unfamiliar) believes it does, but chars. Time and again wood has been the only building material in mills, warehouses, wharfs, docks, barns, etc. that was left with either some or complete integrity after a devastating conflagration. Steel deforms at about 230° C on average, and concrete exfoliates soon after. This is why you will find 200 year old structures that have been "improved?" during their existence with steel I beams melted and draped like spaghetti over the original timber frame superstructure after major fires. It is the WOOD that is kept and restored when these buildings are rehabilitated after the fire...not steel, brick, or concrete...I have been part of several "post fire" restoration of old wood frames...the wood is saved and the rest is sent to the land fill or recycling center.

It can rot...no doubt about that...if neglected. However, so does steel and concrete, which is why our infrastructure in this country is in the condition it is in today. All these materials age, but other than stone, none have proven to be any more durable than the other if properly maintain within their expected parameters of service and design...wood often being one of the most enduring, for the least amount of maintenance. I have been part of enough "cover bridges" to understand that. Often with a steel or concrete bridge close by that has been replaced twice in the same length of time as the beautiful wood bridge has endured with little done to it other than perhaps a new shingle roof.

There are far better material choices, better strength-to-weight ratios, and combinations that work well together.

I must accept that as your personal opinion and respect it. As a statement of fact...well, it is a strictly subjective view, and not based on any substantial empirical evidence. If it was the case, I would be out of work, and there wouldn't be the current demand for it in architecture, as it has been for thousands of years, in countless "wood cultures." Japan's, which has unbroken woodworking lineages that go back over a thousand years, is a shining example of such. In a country as impacted by horrific tectonic events as Japan, and its mega earthquakes and tsunami, if wood was as lacking, and "unpredictable" as you described it...they would not still be building with it over so many of the material choices of modernity. If it was not superior in so many ways to other building materials, this brilliant culture would choose something else, and that is probably why they have wooden structures that are over 2000 thousand years old, and some have even endured atomic blasts. So I would have to disagree with most of your assessment about wood.

And there is probably a good reason for that we know better. I am not sure if anyone has followed these designs that have 'lasted for centuries'” to capture all the maintenance required. We westerners have, we understand that structure is only as good as its weakest link.

There really isn't a good reason, in most cases other than modern arrogance, greed, and lack of understanding...most especially by the "Western Mindset," which is one of the most arrogant (and naive) I have encountered in my travels. I will admit that I find modern humans, keen on "reinventing the wheel" and spending billions on fixing things that aren't broke (usually in a scheme to find a profit.) For the most part, the listed styles of architecture I shared are surviving well enough, and are only abandoned because of "lost skill sets" in their construction, or the "industrial complexes" inability to turn a profit from there level of durability. I for one, believe there is much more for me to learn from history (and its builders) than what I could improve upon it...in most cases. The best concrete known to humankind today...that is...the strongest, most durable, longest lasting (2000 years plus) and under the harshest conditions...was formulated, engineered, and created by the ancients of Rome...not a modern material engineer. Now we are learning that is more like a modern geopolymer than a concrete...so on that front too...we are being "taken back to school" by our betters. Even in your topic of interest RE the mysteries of the Great Wall and Hakka Walled Villages 客家 still hang onto many secrets of there very enduring styles of rammed earth architecture. Like soil augmentation formulas with "lime and rice soup" that still outperforms many emulsifiers of modern chemistry. Modern humans are being schooled by our elders on so many fronts from architecture to agronomy, we really should listen more, and embrace the past, instead of maintaining the hubris that we are better than it. When we do that...we will have actually grown wiser....

Regards,

j

Terry Lee wrote:
I do know wood would never be approved today as a robust building materials.

Well, if steel studs would literally grow out of the ground while you're not looking, we'd all use those instead.

(I hope I'm gauging the level of fun correctly here. If that's too silly, forgive me.)

Mike, that was funny, and should get us back on track of the O.P.

This is a "Permaculture forum" so we tend to lean heavily toward only natural and less industrialized means, methods, and materials. Your word made an image in my mind of a forest with wrought iron trees...interesting to think about but I will take the real ones over that...

I'd just like to say a few words here.

This is the COB section of the GREEN BUILDING forum within a PERMACULTURE forum. We are looking to exchange ideas and information about better, greener, and more natural ways to build and we would like the focus to be on 'natural' rather than trying to justify using less-natural techniques by coating them with green-wash.

Could we possibly steer the conversation back towards that aim?

Thankyou

What about RAMMED bricks laid immediately to form a circular wall house? Would there be issues with drying or strength? I am making rammed bricks with straw for tinsil strength and stacking them right away... Kinda like a cross between bricks and cob. Ideas or suggestions?... will it work? I live in the tropics so no temperature problems. Any comments/advice appreciated.