Thanks! Essential Light Clay Straw by Lydia Doleman, Earthbag Building by Kaki Hunter and Donald Kiffmeyer, the permies.com forums and the videos linked to in the description are all good resources.
Maybe a 3 or 4 days. I used a trencher for another rubble trench foundation and that worked moderately well. See the two blog articles below for that experience. offgridburbia.com/adobe-t-brick-shed-trenching-the-foundation/ offgridburbia.com/t-brick-shed-trench-leveling-and-form-building/
Well presented. Enjoy the voice over technique and the annotations. How were the dimensions of the rubble foundation calculated? Was rebar a local requirement or why did you place steel inside the grade beam form?
Thanks, I don't like talking into the camera so the voice over seems like a good substitute. For depth of the rubble trench I wanted to go deeper then the frost line so 12 inches was plenty. The 18 inch width was primarily determined by the width of the excavator bucket. In Jim Halleck's rubble trench video he recommends the rubble trench be 12 inches wider than the grade beam. I have a natural building book that recommends only 4-6 inches wider. In my case the rubble trench foundation is 10 inches wider than the grade beam.
I put the rebar in to provide tensile strength to the grade beam since while concrete is really resistant to compression is susceptible to longitudinal stress.
@@offgridburbia Appreciate the responses. Still trying to figure out why steel is introduced to concrete as yes, it will provide tensile strength but it will also eventually oxidize which degrades the concrete around it. In normal residential constructs, I have yet to see the evidence that concrete components will undergo tensile forces that would cause failure. Unless of course the component was substandard or misapplied in the first place. And trying to understand why folks who use a compacted rubble footer, speak about frostline when frost and freezing does not effect a rubble support the way it would effect a concrete component. Appreciate your effort to share the building process and the challenges you faced with AHJs.
@@dc-wp8oc Yes, I'm not really happy with using steel in concrete. Anecdotally, I built a cob shed with a rubble trench and a grade beam that was just lime stabilized soil with no reinforcement and that seems to holding up just fine even with extremely heavy walls. For the current build I considered using polypropylene fibers to reinforce the concrete but in the end I went with what was conventionally accepted because I'm wary of experimenting too much with foundations because they are really hard to fix down the road. Regarding, rubble trenches and frost lines I think you're right. Since rubble trenches move water away from the foundation frost heaving should be a non-issue. I've also heard that rubble trenches aren't good for sites with expansive clay(which I have) but I think that's wrong. From my understanding the rubble trench acts like a cushion absorbing earth movement whether its from the frost/thaw cycle or expansive clay. There's just not a lot of data. Just about all the natural building book I have embrace the rubble trench but they stick to going below the frost line depth. I suspect they don't know and are erring on the side of caution. Thanks for the comments. I'm dubious of a lot our current home building practices that produce a product with fairly short life span. Also what's an AHJ?
@@offgridburbia Authority Having Jurisdiction or in our case, building inspectors. On my last project, I did not find them helpful when it came to providing code information. Never once did they have a copy of the code when they came to the job site. And from what I have read, they cannot be held liable for anything they tell you. The inspection department is quick to take your money though. Nice! Thanks for expanding on the topic of rubble foundations. I think current residential building practices stem from just following whatever is considered "normal" for that area, resulting in most construction being over built or over engineered as they say. Keep up the good work.
Great Aaron!! Everything is looking great 👍🏾
Hope everything is well!!
Thanks Horacio!
This looks great! If you don't mind sharing; what were some books/resources you've found useful for your project?
Thanks! Essential Light Clay Straw by Lydia Doleman, Earthbag Building by Kaki Hunter and Donald Kiffmeyer, the permies.com forums and the videos linked to in the description are all good resources.
excellent, excellent vid. im looking into rubble trench for a small house I plan to do
Thanks, I don't know why rubble trenches aren't more common. Good luck with your build.
@@offgridburbia thanks!
that's pretty cool. How long do you think would it take to dig the trench by hand?
Maybe a 3 or 4 days. I used a trencher for another rubble trench foundation and that worked moderately well. See the two blog articles below for that experience.
offgridburbia.com/adobe-t-brick-shed-trenching-the-foundation/
offgridburbia.com/t-brick-shed-trench-leveling-and-form-building/
Well presented. Enjoy the voice over technique and the annotations.
How were the dimensions of the rubble foundation calculated?
Was rebar a local requirement or why did you place steel inside the grade beam form?
Thanks, I don't like talking into the camera so the voice over seems like a good substitute. For depth of the rubble trench I wanted to go deeper then the frost line so 12 inches was plenty. The 18 inch width was primarily determined by the width of the excavator bucket. In Jim Halleck's rubble trench video he recommends the rubble trench be 12 inches wider than the grade beam. I have a natural building book that recommends only 4-6 inches wider. In my case the rubble trench foundation is 10 inches wider than the grade beam.
I put the rebar in to provide tensile strength to the grade beam since while concrete is really resistant to compression is susceptible to longitudinal stress.
@@offgridburbia Appreciate the responses. Still trying to figure out why steel is introduced to concrete as yes, it will provide tensile strength but it will also eventually oxidize which degrades the concrete around it.
In normal residential constructs, I have yet to see the evidence that concrete components will undergo tensile forces that would cause failure. Unless of course the component was substandard or misapplied in the first place.
And trying to understand why folks who use a compacted rubble footer, speak about frostline when frost and freezing does not effect a rubble support the way it would effect a concrete component.
Appreciate your effort to share the building process and the challenges you faced with AHJs.
@@dc-wp8oc Yes, I'm not really happy with using steel in concrete. Anecdotally, I built a cob shed with a rubble trench and a grade beam that was just lime stabilized soil with no reinforcement and that seems to holding up just fine even with extremely heavy walls. For the current build I considered using polypropylene fibers to reinforce the concrete but in the end I went with what was conventionally accepted because I'm wary of experimenting too much with foundations because they are really hard to fix down the road.
Regarding, rubble trenches and frost lines I think you're right. Since rubble trenches move water away from the foundation frost heaving should be a non-issue. I've also heard that rubble trenches aren't good for sites with expansive clay(which I have) but I think that's wrong. From my understanding the rubble trench acts like a cushion absorbing earth movement whether its from the frost/thaw cycle or expansive clay. There's just not a lot of data. Just about all the natural building book I have embrace the rubble trench but they stick to going below the frost line depth. I suspect they don't know and are erring on the side of caution.
Thanks for the comments. I'm dubious of a lot our current home building practices that produce a product with fairly short life span. Also what's an AHJ?
@@offgridburbia Authority Having Jurisdiction or in our case, building inspectors. On my last project, I did not find them helpful when it came to providing code information. Never once did they have a copy of the code when they came to the job site. And from what I have read, they cannot be held liable for anything they tell you. The inspection department is quick to take your money though. Nice!
Thanks for expanding on the topic of rubble foundations.
I think current residential building practices stem from just following whatever is considered "normal" for that area, resulting in most construction being over built or over engineered as they say.
Keep up the good work.
How deep is your frost line
About 6 inches
Did you lightly tamp the rock? Or really try to pack it down?
I guess more of a light tamping. I was just using a hand tamper.