Using Large Concrete Pieces in Earthen Floor Base?

Hi friends,

My hubby and I are currently building a 1000' post-and-beam home off-grid in the high deserts of southern New Mexico and are thinking ahead to installing the earthen floor.

Our home requires a lot of fill on one side, and we were recently gifted with a load of large broken-up concrete pieces from another project that we are considering adding in and compacting around (so as to purchase less gravel and/or move less soil).

But, we have our suspicions that this method of adding large concrete pieces into the base layer of fill soil and/or gravel may...

a) cause the floor to settle unevenly over time;
b) disrupt the natural "grounding" feature of an earthen floor;
c) cause stranger things (?) to happen with energy/moisture/water as it moves around at the ground level;
d) Eff something else up to the point that we may regret the very moment we laid eyes on them?!

Any thoughts or experiences or intuitions? We look forward to hearing!

Hi Brittney,
I am no expert in foundations, earthen floors, or soil hydrology. Now, that I have that out of the way :)....

How big are we talking about? If the pieces are less than 1ft square, I don't think its going to be a big deal as long as you compact over them well. If they are bigger like 5 or 6 foot pieces, then I think it is more likely to cause some weird problems down the road. For the big pieces I would put them as far down as I could and as flat as I could and make sure things were packed under and around them tightly. Or if you had the time and energy, maybe break them up smaller so you still get the volume, but the pieces can pack in more normally?

Great looking beginning, Brittney! I hope you post more pictures as you progress.

I think that if you use the concrete chunks in the lower layers of fill, and bed them well so there are no big air gaps, it should work fine. Be sure to compact the gravel fill so it doesn't settle later. The sooner you do the filling, the longer it will have to do any settling before finishing the floor.

Matt McSpadden wrote:Hi Brittney,
I am no expert in foundations, earthen floors, or soil hydrology. Now, that I have that out of the way :)....

How big are we talking about? If the pieces are less than 1ft square, I don't think its going to be a big deal as long as you compact over them well. If they are bigger like 5 or 6 foot pieces, then I think it is more likely to cause some weird problems down the road. For the big pieces I would put them as far down as I could and as flat as I could and make sure things were packed under and around them tightly. Or if you had the time and energy, maybe break them up smaller so you still get the volume, but the pieces can pack in more normally?

Thanks for your inquiry, Matt! The chunks are more around the 1 ft size, some a bit larger than others. I do like the idea of breaking the larger ones up a bit.

Glenn Herbert wrote:Great looking beginning, Brittney! I hope you post more pictures as you progress.

I think that if you use the concrete chunks in the lower layers of fill, and bed them well so there are no big air gaps, it should work fine. Be sure to compact the gravel fill so it doesn't settle later. The sooner you do the filling, the longer it will have to do any settling before finishing the floor.

Thanks very much, Glenn! We're excited and in-joying the process. That's a great point about getting the fill in there ASAP. I've actually been avoiding starting the process because, you know, the joys of lifting all those big concrete chunks... X) But I do believe you're right about the settling and am grateful for the inspiration to get started sooner rather than later.

If they are small enough to move by hand, they should work fine. Follow the rules for hugelculture and put plenty of dirt around each piece. But compact the snot out of it. There should be enough dirt around each piece that it won’t affect grounding or drainage more than any other fill.

Urbanite also make great flagstone patios or rock walls if you don’t want to mess with it as fill or have more than you need.

How’s the process going?

I am prepping for an earthen floor next year, currently have a compacted gravel subfloor. I am planning on pouring a tiny concrete foundation for our kitchen island and still covering it with earthen floor.

How has progress been coming along, any trips for putting concrete under earthen floor?

Scott Lawhead wrote:How’s the process going?

I am prepping for an earthen floor next year, currently have a compacted gravel subfloor. I am planning on pouring a tiny concrete foundation for our kitchen island and still covering it with earthen floor.

How has progress been coming along, any trips for putting concrete under earthen floor?

Hey Scott! Congrats on your upcoming earthen floor. We're in-filling with soil right now and, as the wise R Scott has suggested, "compacting the snot out of it" with a steel tamper. Later will come drain rock, followed by road base... we plan to rent a Jumping Jack in the near future.

Your idea for pouring a foundation for your island is an interesting one! What are your considerations around that? Our oven is located island-like also, and I hadn't thought that far ahead. Afraid I can't offer any tips myself (this is our first rodeo, so to speak), but I'm intrigued to hear this about your plan.

My thinking for pouring a small concrete base is to embed steel brackets in the concrete to attach the island to. I’m not sure how else to affix the island to the floor that is done in a way that a solid hip check into the island won’t crack the earthen floor.

I looked around for advise and cannot find any at the moment.
I will get back to it though.
But look here anyway.
https://permies.com/t/58629/years-living-cob-list-wished

I am also wondering how to attach a toilet to an earthen floor…