How to Build Straw-Clay Walls | Building a Straw-Clay Tiny House - Part Three
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- Опубліковано 13 гру 2022
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Well this video just convinced me to stick with regular straw bale construction. What a pain... Thanks for the vid
I really like it
If you use more clay in the straw it will be easier to compact and will have even better overal quality and durability. A clay and straw mix lasts for hundreds of years without rotting. Friends of mine opened a wall made with that mix fro a building of the eighteenth century and it was intact.
The straw then was thicker aswell
I saw someone do hemp-lime crete round house looked solid af
Great series. Really neat seeing it go up over the last 3 videos. Excited for part 4
Glad you enjoy it! Thanks!
What is the ratio of mud water? How much of clay and how much of sand need to go in there?
What consistency is required for the straw and mud? Too watery or not too watery or a bit dry?
In what intervals/when to move the frames to next iteration? Because it's not ideal to move immediately and keep compacting.
Do we need to treat the straw for termites?
I've been to a course in permaculture for cob light clay straw and earthbags. The real answer is not a mathematical ratio but a feeling in your hands when you know it's right. However, the number get you close. Clay is wet as is, but you make it wet straw/ clay. There is not and sand or mud in a true clay straw. That's in the cob or plaster
Borax should work against termites. In the clay water
The material is cheap but it is labor intensive so in the end no much of a saving depending on the labor cost in your area. Of course If you have a half of dozen friends to help it reduces the cost I like the fact it is the healthiest and most environmental material once could use to build a house.
I see labor intensive as a plus.
Labour intensive can mean for some bringing the community together to share and pass on wisdom, enhance community spirit and get fit ;-) But this isn't always possible for everyone 💗
Poor people may have more time than money and no need to get it done in a day.
There are many benefits of building a small house. Lower energy costs, more communicative, intimate family unit, and perhaps most importantly of all: quicker build time.
I don't know about you guys, but I know I would NEVER want to build a cob house the size of a mcmansion knowing how long it can take to build up even a small cob house with 30 people working on the project at the same time. I've seen conventional houses and even large hospitals built up in a matter of weeks far faster than cob houses can be.
Super nice brickwork. Impressed!
I would love to see how to do a second story/loft in a cob building.
You can do multiple levels in a cob building. You just have to slope it inwards like it's a subtle pyramid of sorts if you're doing more than two stories.
Thanks for this information, I've found it difficult to find decent info on light earth on the internet. Looking forward to more videos! 🙏
What about if I put some lime in the composite ?
Thanks for the video
Thank you for the very informative material!
Regarding the difficult parts in the upper side of the walls, I was thinking about making 1 slip-straw brick for each space. I'd just cast it on the ground, let it dry and then place it up there. What do you think?
Hempcrete would make a better building envelope and your material cost would go up but your insulation value would drastically increase and you could also eliminate a lot of the thermal bridging at the studs.
Yeah, I just found a source for hemp shiv. I want to do a hempcrete building sometime soon. The straw-clay is definitely cheaper though, which was nice right now.
I'm curious about this...they say hempcrete is generally 1.7 R value per inch. How does light straw clay compare in R value?
Also ... Can't you bury the studs with straw clay just like is typically done with hempcrete? After all, they are both compacted into forms, and the construction process seems the same - just different materials?
Hemp does the same as straw. Its just the hype that makes it more appealing. But in practical terms it's the same.
Hemp is fireproof straw isn't.
It's worth checking out the Cobbauge project over in the UK. They developed a dual layer light cob and dense cob to have a reasonable thickness on monolithic cob structure that could pass UK and French building regs (30cm light cob and 30cm dense cob). They tested reeds, straw and hemp shiv for insulation value for the light cob and hemp shiv came out best. If not using the dense cob beside it and using timber frame for structure though, I wonder if maybe a 5% straw 45% hemp shiv mix might be worth trying to get some of the structural quality of the straw for binding the light cob, as their light cob mix with hemp shiv was very friable, like breakfast cereal. May also need to use a metal grid for the forms and leave in place longer as would need longer to gain structural strength from drying. I'd say you'd definitely be wanting to render/plaster with lime/clay plaster to further lend some structural integrity. They've various academic papers reporting on their experiments, so useful data when talking to officious folk. They've also some really useful practical guides and videos for builders and architects.
My cabin has rough cut 2x6 walls and R22 batt insulation. To reach that level with straw bale the walls would have to be 18" thick!
But will it still be standing when the big bad wolf comes?
If you live in Minnesota, their construction codes now mandate all new construction housing have 30" (2.5 FEET!) of spray foam insulation.
How wet with muddy clay are you getting that straw so it holds form when it drys?
Is there a ratio of water/clay to straw? It seemed very dry when you were mixing and compacting. Also assuming it has to stay above freezing for a period of time in order to set/cure properly?
There's no set ratio that I've ever come across. Some people prefer a more 'muddy' mix than others. I actually do too because it compacts a little easier. However, my soil would not dissolve to the muddy consistecny to do that so it was more of a 'lite' covering of muddy water. This is how most straw-clay tends to be though. Just a runny muddy water covering the straw.
@@thiscobhouse We got the clay from a farmer for free. We sieved the clay and dissolved it in water in larger basins (sawed open old metal tanks from the scrap yard). Then we put the straw in it so that it was completely soaked. At the end, we placed it in the formwork and compacted it. It takes longer to dry, but it makes the walls very solid. As you said, compaction is easier. Greetings from Germany
Can you use chopped straw?
Amazing!!
Thanks!
Nice man. Looking forward to seeing it finished.
Thanks 👍
Thanks for this great, informative video! I am planning on building a straw-clay structure much like this (but quite a bit bigger) in South Africa. I have a question that may be a little silly, but hey I am learning ! I noticed that there are no diagonals in the wooden structure. I understand that they would pose difficulties when filling , but how do you maintain the structural integrity of the building without diagonals? Does the straw-clay do their job ?
Yeah, basically. Once all the vertical trusses are set, and the top plate is put in place over the tops of them the framing is rigid. Then the addition of the straw-clay adds even more rigidity to the walls. Plus, the roof too.
@@thiscobhouse thanks so much ! Really appreciate your feedback .
For a better perspective of the amount of straw needed. Please clarify on average what is the weight of the 35ish bales used for this build?
I was surprised to see you using rebar for horizontal structure, as I imagined it might create recurring condensation in the middle of your light clay structure. But I also noticed it was red, as though sheathed with some sort of plastic insulation. I'm no builder so am not a connoisseur of rebar, perhaps you could explain whether this is an isdue and if a particular type of rebar is recommended?
I used a fiberglass rebar in this one. Tbh, I'm not too worried about the condensation issue either in here. Perhaps it could happen, I don't really know. But if it did, the moisture should be able to escape easily before any problem occurred. Just my first thoughts anyway.
Чем ты делаеш жыдкость? Штоб потом наливать на малому..
Just one question... How would you insulate the first part of the house, where the bricks are? Thank you, from Spain.
You could either not do the brick, and bring the straw-clay walls down to the floor, or you could install insulation in the middle of the brick wall.
R12 - you dont have snow do you? Context is important. I am here to learn to use this build idea. Thank you!
We are in a temperate climate with only small amounts of snow. Just increase the R value by making the walls wider. The larsen trusses can be built to whatever width you need.
I was thinking the same. A single 2x4 wall has an r value of 13.
So much framing and grunt work. How is this quicker, cheaper or better than straw bale?
Nobody is saying its better than strawbale. Every wall system has it's own pros and cons.
I like this straw-clay method because the framing provides load bearing (also good for getting permits), and the straw is preserved better in the clay mix. But to each their own.
But honestly, the wall framing is the easiest/fastest part of the whole build, imo.
Can I use pine straw?
Are you not worried about water damaging the exposed straw walls?
Not at all. The high foundation and the long roof overhangs protect the straw-clay walls. At the end, the walls will be covered with a waterproof lime plaster too.
@@thiscobhouse Does the Lime plaster add any r value or is it too low to matter? Thanks, Alex! Great content!
The lime plaster is relatively solid and not a significant contributor to the r-value.
Is there a video comparing rammed earth to straw-clay? Its the same as cob it seems?
This recent video I did might help answer some of your questions: ua-cam.com/video/Hme0sb_1Kvk/v-deo.html
How much do you charge to build these types of houses?
I'm wondering what the wind load would be on these walls? If you are going for super strength walls then would it be ridiculous to do the Larson trusses with 2x6 or 2x8?
Not ridiculous, but probably not necessary. I can't measure the wind loads, but I'm sure this building can withstand A LOT.
The depth of the top/bottom chord doesn’t add to the strength of a truss. The depth of the web does. You could probably even get away with a 2x3.
How to grow my a tree in blackjard??
Definitely the wrong video to ask this question but, I do hear eucalyptus regnan trees grow quickly!
I must have missed it, can someone tell me what the R Value was for these walls?
About R 1.5 per inch of thickness. I think it can vary depending on how compacted the straw mix is though.
The wooden frame isn’t insulated. Doesn’t that create a cold bridge?
Sure does!
@@thiscobhouse Oh yes, I reviewed the video and you can put the clay straw between the trusses. Great video. I learned a lot.
So an R value of 12 for 9 inches - or about an R value of 1.3 per inch? That sounds kind of low... or are you counting on a high U value as well? This doesn't seem like it would do well in a really cold climate unless it was really thicker walls?
The walls are generally wider than what I'm doing here.
I have a suggestion. What if you made a seperate frame on the ground and did a compact let it settle, removed it by taking screws out and installed it at top where its difficult to reach.TRY IT
You say that the straw-clay has a pretty good r-value and is cheap to make. The industry doesn't like that so you better go to the bank and barrow thousands just to buy roxul :-) Here in Nova Scotia you are not even allowed to use your own lumber for your house.
Canada is communist.