Dipping straw bales into a clay-water mixture

I saw this video on yt: https://www.youtube.com/watch?v=7J0862TFPwU

Does anyone know why this is done? adding clay to the straw? I am guessing that it has to do with making it more structurally solid, or protecting the straw. If it is useful, would it be possible to saturate the full bails in this clay-water mixture and let them dry for a day or two? Yes, they are going to be much heavier - maybe twice as heavy? The way it is done in this video is labor intensive - to make the clay water takes 3 steps, then ripping apart the hay bails, mixing the two, setting up the forms, then foot stomping the coated hay into the forms.

If it could be done with full bails, then give the bails a few days (1 to 2 weeks?) to dry...perhaps turn them over and do it again...I am guessing the bail would be quite solid and less likely to settle once it has been placed. If lime were added to this, a greater degree of waterproofness (if there is such a word) might be achieved, and a more durable structure all around could be built. Cost should not be increased significantly. The time would be increased only because of the need to dry the bails.

Any thoughts?

It looks like they are not using bales but infilling with the straw-slip material. With the exposed studs there might be an additional siding step that is not shown in this video.
The weight of a straw bale is pretty easy to manage as compared to a bale that would be dipped into a clay slip prior to placement. My experience has been that occasionally there has to be a bale size adjustment during the build in some areas so there would be a cracking of the seal so to speak as you cut a coated bale.
Code wise it might be easier with this type of construction to pass in areas where they do not allow bale construction. Financing might also be easier since it appears to be a typical frame building replacing insulation with essentially stud width/depth adobe bricks.

- This appears to have been video'd near Madison Wisconsin, and this Construction would lend itself to a decent R-Value with little or no stumpage of insulation, indeed

There is a period where the slip-forms come off where the quality of the work is immediately visible. This whole project is a weird blend of Gunnite meets Hempcrete,

Papercrete, meets stick house!

While an inexperienced team of people could be turned loose at THIS stage of the project, there is a lot of room for interpretation of the term ''Best practices''

Conventional (cheap) and traditional (labor intensive )

All in all its easy to have mixed feelings about this one ! Big AL

Hi Tom,

This process has actually been around in some forms for a very long time. Currently the generic term is “Light straw (or chip) clay” work.

Does anyone know why this is done?

Yes, it is a binding agent to allow a rammed infill system to stay together. “Clay glue” if you will.

adding clay to the straw?

Wasn’t sure if this is a question of statement??
Anyway, yes adding clay, historically, it’s been added to many mass wall systems either as a densifier or binder…Often both.

I am guessing that it has to do with making it more structurally solid, or protecting the straw.

Hmmm,
Yes to the first part…and other elements as well. As for protecting, I suppose in some instances it does that as well.

If it is useful, would it be possible to saturate the full bails in this clay-water mixture and let them dry for a day or two?

More like months and that is the issue if outside the dry desert biome…the bails can’t get rid of the intestinal moisture effectively enough to warrant the treatment. This was part of the reason some bright folks dusted of some old methods and brought them back to life as a building method breaking up the bale and making a system to infill with, as is done in several vernacular forms of earth architecture…or variation thereof.

The way it is done in this video is labor intensive - to make the clay water takes 3 steps, then ripping apart the hay bails, mixing the two, setting up the forms, then foot stomping the coated hay into the forms.

This is a example of the “contractor” method. People, machines, and added power elements and up to speed. You could (more so in the past) add just more people and get similar results. I would also wager that he might be a tad “gadget driven” as the much “processing” of the soil seems excessive for the results. If he processed less the results may not be as refine (very nice work) as he has achieve…yet…for an infill wall method I’m not convinced it is necessary to go to quite that extreme.
Remove all of the people, and machines (most of them anyhow) and you just have to add time. With a professional building crew that works in natural and/or traditional modalities of architecture they could probably spec out a small house like the one in the video in lest than 6 to 12 weeks depending on location. Double or triple that (maybe more) for a novice DIYer.

If it could be done with full bails, then give the bails a few days (1 to 2 weeks?) to dry...perhaps turn them over and do it again...

Some folks out west have successfully (and more unsuccessful I suspect) have experimented with “dipping” bales in clay slip to “mortar” the bales together. Bales are dipped, then clay mortar is used to bind the bales together which allowed for easier plastering…and...a lot more work in the project for little gain. So, I haven’t heard of anyone doing it in the last 15 years…

I am guessing the bail would be quite solid and less likely to settle once it has been placed.

Bales don’t settle too much as it is…especially in a good infill job with dense well pack bales and proper placement within the framework.
If lime were added to this, a greater degree of waterproofness (if there is such a word) might be achieved, and a more durable structure all around could be built.
Good track of thinking but it tends to promote decay. However, there is some experimenting with the concept. Hemp-Crete is just a commercial form of “light straw clay” infilling systems and I am sure there is someone out there trying lime instead of clay. I have experimented with it (expensive) and with a proper amount; more of “dabbling” could achieve something workable. I stop such things usually because I am a big student of ergonomic, and not wasting my time reinventing wheels…as there is typically (not always) a vernacular traditional system that is good or better to fit regions architectural goals.

Hope that shed some light on it...

Regards,

j

Jay, the processing is necessary to insure a consistent, quality result. I am not sure that the label, "gadget", is necessarily called for. Their tests showed that proper processing was key to achieving competitive R-values.

I corresponded with them a couple of years ago about the possibility of using a baler to make blocks or panels. They were already considering the idea, but had not secured a baler for experimentation yet. Pre-dried blocks or panels could solve most of the moisture and manpower problems.

Nice answers! If a form the size of a straw bale were made, could the straw/slip mixture be pressed into the form to make a straw/slip brick - about the same size as a straw bale? Let to dry for a short time and then handled like a bale - maybe also bound again - and then stacked in a fill system without forms? One of the reasons behind my questions in these forums - I am teaching in Asia now and am only home for 3-4 weeks in the summer and a little less than 3 in the winter and am need of securing a retirement home within the next 3 years (no, retirement will not happen till much later). Unfortunately, I am not related to Bill Gates....also, I have somewhat of an "ecological" conscience, hence the time spent on (and enjoyment derived from) these forums. To further illustrate my thinking: If these straw/clay bricks were feasible, I could make them in the winter, while the foundation was being dug and poured...then in the summer, could do the assembly. Also, relating to a question I had about earth bags. if the bags could be filled by a machine (there is a stone and gravel shop that sells bagged products about 30 miles away, privately owned, which usually means that they are anxious to find side work during slow seasons) it seems that the actual construction time could be greatly reduced. I have also inquired about making very large rammed earth blocks for the same reason - time to get the walls and roof up will (hopefully) be reduced. Finishing the interior can happen on another trip but it is important for the security of the dwelling to be able to lock things up. Also, once the roof is on, the interior is protected from the very frequent and heavy rains that this area experiences. Concrete walls can be poured and tilted up in the blink of an eye, but I would like to stay away from the use of this material as much as possible. It does seem, however, that many alternative means of construction can benefit from the use of a little bit of concrete. I wonder if a little bit of concrete were added to the clay slip if the result would be a stronger, more well preserved house?

Tom, pre-dried blocks of light clay has been done successfully. I don't think it would be too difficult to cobble some together yourself. The key, I think, would be making the blocks a manageable size and quick to dry all the way through. I don't know if anyone has been successful in making blocks or panels using a hay baler. Keep in mind that these blocks are for non-structural applications. They are not adobes. There are commercial wood chip/fiber products (Faswall, Durisol) that use some type of plaster or cement as a binder. Here is a patent from 1926 by Buckminster Fuller's father-in-law, James Monroe Hewlett, that gives a good description of such a process.

i have always called this light clay straw..... small difference, so perhaps it doesnt matter, and i have seen the words used interchangeably. it just stuck in my head that way because i thought it was a reference to the clay being light, as in slip clay is used, not a heavy clay body. then again its called many things, straw clay, light straw clay, or light clay straw.

IMO it is one of the best, easiest, and beginner friendly ways of earthen building, but it does need some other forms and structure to carry the weight of the building. it doesnt make load bearing walls, just an infill and is used for finishing and insulation. that may be one of the reasons its one of the easiest and most user friendly, because you dont have to be trying to make load bearing walls, with straw bales and cob and etc, thats a movie itself to figure out how to do that. where this blends with other methods of building, a "conventional" house could have this just for infill and insulation, with post and beams for weight and structure, much easier for many to wrap their heads around making it structurally sound.

i agree about not needing the gadgets, not that i am wanting to pick apart what they are doing, if it worked for them thats great, but for someone who wanted to repeat this, it is not necessary to have all those gadgets. you could do the same thing with some buckets or other containers and a good screen, using a hose for pressure to push raw dug clay through the screen. it's pretty beginner friendly and it doesnt need to be precise, but for the best results you want to use slip clay, not just any clay like dirt. i did like their adding bamboo poles to the walls, that was a clever trick that i will file in my brain for further thought =)

to get slip clay you use the tendency of clay to settle and stratify into different weights. once the clay is dug and screened, with water added, it will settle into different weights within the container. after letting it settle for a bit, pouring off the very top into a separate container will give you the lightweight slip clay that you want for this. the sand and rocks and heavier clay particles will sink to the very bottom (or get removed while screening), while the top half (or so, hard to approx) will be the lightest clay particles - "slip clay". its pretty hard to go wrong at this, its really quite easy, no heavy machinery needed! the only ways you could possibly go wrong are if the dirt you have has little to no clay, or you make it too wet. but making it too wet just means you wait a while for water to evaporate off the top, or once it settles really good after a day or two, pour the excess water off the very top, keep letting it settle again, and pour more water off the top till you have a consistency that works.

its been many moons since i was last doing any earth building, but i did do some projects working with forms, like was suggested here, basically doing something like this light clay straw but with small squares. although actually you use a lot more clay, and use a heavy body clay with the sand and bigger rock pieces to help it stay together better. it is also a good method, stronger and more forgiving that cob or straw bale, easier to make a bigger structure or several stories, the mortar matrix between your blocks is a large part of the load bearing and structural integrity.

heres a few web pages with some more info:

http://www.designcoalition.org/articles/Natural_LHJ/liteclay.htm

http://www.theyearofmud.com/2012/03/01/light-clay-straw-house/

well google is letting me down searching for pages with "forms" is bringing too many irrelevant results....

but anyway - everything thats been talked about here is a way of building with FORMS, either slipform (where you move the forms like in the OP video- light clay straw, or even slipform building with stone), flexible forms - eathbags - or working with earth block forms.

i know theres some great info online, but like i said google is not listening very well today =) i found a few to link here, but not what i was looking for. these are more concrete based ideas, as opposed to doing this with less processed materials. but still hopefully some food for thought and some good info to research. not all form blocks are "compressed", and not all slipform or block walls use concrete as a mortar. but anywho, some basic info.

i am most interested in these ways, and i think anything with forms is preferable to other methods of earth building.

heres something about compressed earth blocks

http://www.oskam-vf.com/CEBS_living_building_material.html

http://www.ecohabitar.org/wp-content/uploads/2012/01/04-5793-1.pdf

and some about slipform:

http://digginginthedriftless.com/2012/05/08/building-a-rock-wall-using-slip-form-part-1/

http://www.motherearthnews.com/diy/stone-masonry-primer-zmaz96djzgoe.aspx#axzz3K17TwaUV

Hello Andrew, et al,

I am sorry if umbrage to my term "gadgety folks" was taken. I find "gadgety folks" very interesting and usually entertaining and creative, so please do not take my term "gadgety" as an insult, as it was not meant so.

I must further stress to other readers of this thread, that the level of processing may indeed be necessary for the system depicted in the video just because of the "mechanisation" of the method this individual chose...which is fine.

I must really make clear for the body of our readers interested in this system of building, It is far from necessary in the overall modality of this architectural form, nor has been for the millennia it has been around. This is not, by any means, a "new method" of building. "Light Cobb" methods and related "clay wall slip forming" has be around for a very long time in several cultures.

Hey Leila, these links below may help...I would love to answer any question you or others may have...

"clay straw bale"

"clay slip straw"

"clay slip wood chip"

Thanks! Can the slip be added to a bale without disassembling it? I can wait 6 month - possibly even a year - to let them dry out. The first structure that I will put up is a greenhouse, a perfect place for drying things. If I understand correctly, if the slip can be added to a whole bale - drizzled over, then rotate the bale, etc - labor will be greatly reduced from the notion of disassembling the bundle and then making the tossed slip straw salad....then packing it into the forms.

Tom Connolly wrote:...to let them dry out. The first structure that I will put up is a greenhouse, a perfect place for drying things...

Hi Tom,

I think your goals of "pre building" are wonderful...

I also believe, any any architectural build, one must fully understand the entire plan...including...the location and foundation this architecture will be built on. From an "ergonomic perspective" I am not sure pre fabricating brick, bale, panel system, etc is going to be the route to follow, as the effort for the gain is going to be dramatically more work in material handling. As a Timberwright, Mason, etc, I am acutely aware of how many times I have to "handle" a component item, be it a timber, stone, bale, or chunk of clay.

I think stockpiling your materials is a grand plan. I also encourage many that I have worked with to take as much time as possible to plan out completely their design...the more time the better. Don't ever start a project until there is a complete "drawing" and/or "modeled" plan of what you are going to build, right down to mechanical and electrical elements if they are part to the system. Every detail possible should be drawn out and designed of paper (or CAD) first, as mistakes there are the least traumatic.

I would also have to challenge that a "green house" is a good place to dry anything...for the most part they are way to "moist and humid." As for soaking or saturating a bale with slip...that would be a big NO!! This could well lead to decomp of the bale, and this system in general is aimed at more arid regions. If the links above are gone through in detail, some good (and not so good) ideas can be found. "Mortaring" bailes is a method that has some merit, but not necessary at all for a great bale build. I also feel that "clay slip straw, chip or other fiber" as an infill method is superior in so many ways to other methods.

Regards,

j

Greenhouses are not humid by design. They are humid by use.

Tom, you could use your greenhouse to dry blocks, but you would need to tweak it a bit first. You need to to ventilate it properly and you may want to preheat the air that feeds into it. Growing plants is what makes a greenhouse humid, so don't grow plants while you are drying blocks. Here is an article about a commercial solar drying tunnel design: http://www.hindawi.com/journals/isrn/2012/890820/

You could preheat air with a black plastic tunnel inside the greenhouse and build a solar chimney (also black plastic) to drive the ventilation.

If you want to experiment saturating and drying a whole bale, I would recommend that you perforate the bale ("tenderize" it) to facilitate passage of slip through the center of the bale. See how far slip penetrates the exterior of the block after a quick dip, then make perforations spaced accordingly. There is still a very good chance that it will fail on many levels, but it might work -- maybe, possibly. I think that trying to simply soak the bale for a long time would only result in the bale acting as a filter, soaking in the water and leaving the clay outside.

http://www.toolbase.org/ToolbaseResources/level4TechInv.aspx?ContentDetailID=973&BucketID=6&CategoryID=13

Does anyone have any experience working with this kind of strawboard? better yet, making it?

Similar products have been around for quite awhile. They don't seem to have ever caught on in the US, though they are very popular in China. The high pressures and high temperatures involved in manufacture would make it difficult to do yourself.

You might be interested in StrawJet. Still capitol intensive, but you might be able to cobble something together that approximates it. Also, do a search on straw rope.

Interesting...but trying to fabricate that kind of machine...looks like it is specialized enough to the point where it would not be possible for a person with non-professional skills (metal fabrication, etc) to do.

What exactly is the benefit of using straw and slip together? Is it to protect the straw? Does it provide a higher R value? Would there be any greater benefit of using a small amount of cement - say 5% in with the clay? My objective/hope is to find some way to make a kind of thick (even as thick as a bale of hay) fiberboard out of straw (even other green materials) & clay and maybe some other kind of stabilizer. It would probably be helpful to chop the straw up a bit in order to make smoother walls.

Tom, What you are proposing sounds more like a Faswall type manufacture. Make sure you read the patent I referenced earlier. Using clay and/or cement/geopolymer as a binder will result in a more brittle panel than what is achieved with the heat and pressure treated straw panels, but it could be doable. It would take a lot of trial and error to get the right balance for a workable, durable panel. A block might be more appropriate.

I think that the clay, once the water from the slip evaporates, provides protection to the straw, or chips, from moisture and vermin and it glues the straw or chips in place. It does not provide more insulation than untreated straw, and can be a lot less insulating, depending on how much clay you apply and how much you compress it, but once dried is more physically stable and will last a lot longer than untreated straw.

The Chinese used a heavily tamped straw clay, using a thick slip, to make storage silos back in the '70's: http://books.google.com/books?isbn=9251011540

Here is a Thai adaptation using vetiver grass: http://www.journal.au.edu/au_techno/2004/jan04/vol7num3_article04.pdf

The straw clay silo walls were strong enough to hold in the stored grain and they provided some insulation.

I have considered hybrid walls using a compressed straw clay skin surrounding a light straw clay core. You could do the same with cob.

Some musings. "Conventional strawbale" construction normally involves plastering over the bales once in place. The bales used for loadbearing strawbale construction are denser than a regular bale. A regular bale runs eighty pounds or so, the denser construction bales a hundred pounds or more.

Strawbale may be done as infill with a timberframe, or it may be the loadbearing wall, but either way, it is effectively big block masonry. In other words, putting up strawbale walls goes pretty quickly.

A bit brittle is OK - hopefully the house is not going to move anywhere My main concern would be any loss of insulating value by the addition of the clay.

Good musings...the larger the building material, in general, the faster it goes up. Maybe my original understanding was incorrect, but I was under the impression that a straw/slip bundle or block of hay was a better protected block of hay - more likely to last a longer time, hence the consideration to rip a nice block of hay apart, add clay and then try to put it together again in some form. I know that the inside and outside wall coverings (stucco, etc) are supposed to protect the hay, but if done by an amateur (myself) with limited experience in this technique, I would feel more comfortable with a double layer of protection. I am guessing that by the time I finish the home, I will have pretty good skills

What you need to build is a small out-builiding, something to develop your skills before you even consider something larger, like a house.

The amount of insulation will be in reverse proportion to the amount of clay left on the straw. Generally, if the resulting straw is still a golden color after drying, the clay coverage is good for insulation, approaching that of untreated straw. The gadgetry referenced in your first post helps a great deal in getting the right balance, consistently -- but it will still need some experience. You could do it in a more labor-intensive way and get similar results, after a lot of experience.

If you are concerned about the longevity of untreated straw in a straw bale house, try to find examples in your area, or a similar climate area, that are at least 30 years old and see how they have done. With proper encapsulation, it may not be as much of a problem as you anticipate.

One thing to consider is the scarcity of small bales. Most farmers now use balers that make large compacted bales. If they keep a small baler, it is to meet market demand and they will charge a premium price for those bales. If you are going to unpack the straw for processing, you can buy the larger bales, hopefully for a significantly lower price per ton.

Andrew Parker wrote:One thing to consider is the scarcity of small bales. Most farmers now use balers that make large compacted bales. If they keep a small baler, it is to meet market demand and they will charge a premium price for those bales. If you are going to unpack the straw for processing, you can buy the larger bales, hopefully for a significantly lower price per ton.

That was one of the attractions to the clay/slip method. It does not require baled straw. By unbaling it, however, there is a great convenience lost and much more work created.

Where there's a need, there's a gadget. Do a search for mini baler, home made baler, or manual baler and you can review dozens of possible solutions to repacking straw. It would appear that the most tedious part of the whole thing is tying the bale.

If you are baling slip coated straw, you may not need to tie the bale. You would need to wash down the equipment periodically to keep it from getting gummed up, especially important if you have added lime or cement to the slip.

For panels, you would want to lay the straw down in a pattern that maximizes tensile strength. For a block, you just push the straw into the form.

Another search term for this is lichtlehm (light loam)

In the traditional medieval use for the infill of timber frame construction, the straw had some seed in it leftover from the harvest. The moisture from the slip let the grain germanate. Some of the sprouts got out, and their root system dried out the wall. You left the wall to 'grow' until it dried out the wall completely. The root mass helped hold the wall together, and the stubble of the sprouts helped hold the plaster on.

The slip has two functions: One is to bind the straw together. The other is to make it flexible so that it packs more easily.

If you wanted to soak bales in clay, standing them on edge after and poking some grain into them may be a good way to dry them out. Or poke them in, and build your wall.

Slip straw is not as good an insulator as fiberglass. You need a thicker wall.

I saw one vid on youtube where they were packing it into 2x4 on 16" spacing. This seems to me to be silly.

A: You are wasting a lot of 2x4. The only reason for 16" spacing is to support drywall which is very flexible.

B: A lot of the awkwardness is on a per cavity base. Three 16" cavities is a lot more awkward than one 48" cavity.

C: A thicker wall isn't a lot more work than a thin wall. Use a wider tamper.



Unlike strawbale, slip straw isn't structural. You can't keep the roof up with it. More like hempcrete that way.

The top of the wall in slip straw is awkward to do. This is where having some form of preformed material would help.

I can see merit in a timber framed style using engineered wood I-beams as the elements. This would minimize wood use and thermal bridging, while at the same time allowing a much thicker wall.

Fire resistance is also worth considering, not just insulation or structural support.

A slip clay (leichtlehm) traditionally was coated inside and out with either clay or lime based plaster, then white washed.

straw construction when plastered is far more fireproof than common stick built buildings.

Also, strawbale walls are compressed and will not fall apart like the single bale. I have heard that they just smolder, and that's not considering finishes typically applied to the surfaces.