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"House Dam" design... or Compressed earth berm house

 
Tom Harner
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Ok, so I have seen this house design described by Bill Mollison, Jack Spirko and geoff lawton now... I love the idea and want MORE information. I classify this building style as distinctly different from the wofati design in that the exterior walls are themselvs made from as much as "6 meters" of compressed subsoil.

Unfortunately, the only video that I can find on the open interwebs (you try googling "compacted berm house") is Jack Spirko's, the least detailed description of the house. Thank You Jack for putting it out there! This was actually the first video I saw on it; it is/was a GREAT primer for recognizing the value when I heard Bill (and now Geoff) describe the same design.
https://youtu.be/gxtKOqkEqw4

As Geoff describes it in his PDC video (Climate, Minor Landscape Profiles: Flat Lands), the house's exterior walls are essentially a compressed soil pond dam/levee that is turned the "wrong" way (by 180 degrees). Instead of catching and storing tens of thousands of gallons of water above its mass, it displaces the water around itself.

Why won't it work? What are its flaws? Can those flaws be resolved? Does anyone have a link to a better explination?
 
Andrew Parker
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It is probably fine as a landscaping feature, but if you wanted to use it as anything more than emergency shelter, you would need to stabilize the interior walls to assure that they would not collapse in on folks and hold up the roof. Would you be putting a PAHS umbrella over the berm as well?
 
Tom Harner
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I don't know about the PAHS umbrella but can see no reason not to...

Why would the inner walls need to be reinforced? Rammed earth walls are often not reinforced and they are only 18 inches thick opposed to 18 feet thick.
 
Andrew Parker
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When you are dealing with that much mass, the lateral pressure is pretty high, so from that standpoint, 18' is not better than 18". You need to either slope the sides, shore them or otherwise reinforce them in some way. Compaction can lessen the effect of lateral pressure, but tamping with a backhoe or even a front-end loader is not likely to provide a lot of uniformity.

Rammed earth is compacted until it begins to give a metallic thud or ring. Dirt (not any old dirt, but dirt hat has been analyzed and prepared) is usually layed down in shallow layers and then compacted by hand or with a mechanical tamper until the desired compaction is obtained, then the next layer is layed down, and so on. Dam construction often utilizes large road rollers.

When dirt is piled up for highway construction, it is usually left in place for a time, often a few years, to settle and consolidate before getting its final shaping. Even then, a vertical wall is reinforced.

People die every day from trenches and embankments collapsing. Don't underthink things when dealing with tons of dirt.

While I am throwing out the negative waves, I will also mention that you need to anticipate some settling as the additional weight of the mound pushes down on the soil it is piled up on. Another reason not to trust a bare, unreinforced vertical cut.

With the sobering content taken care of, I think that using the dirt excavated from a pond is a great solution for building a flat (low slope) terrain wofati, or a raised platform for flood prone or soggy areas. It is certainly doable, but not without complications. The problems are very old and solutions have been around for thousands of years, and there are some nifty new ones as well.
 
Tom Harner
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Yea, Jack did suggest using the bucket to tamp the soil... Bill Mollison described the process as using a dozer to do the compaction (add a few inches of soil, driving over it to compact it, add a few more inches, driving over it to compact it, etc.). That would help with the compaction consistency.

I would also expect to install a keyway and compact the subsoil underneath the berm as well. Though I'm sure you are right that there would be additional settling below grade.

BTW, I asked for negative reviews. I want to know why it won't work before I risk my family's lives (or someone else risks their lives) constructing a dangerous building. But like I said, three well respected people in permaculture have described it now (one being a review of another's suggestion). Geoff even claims to have built one but was a little shy with the details (in his defense he referred to it as an example of flat land's potential, not as a suggestion). If nothing else I want this to be a place where people can find out the potential dangers of the design if they google it like I tried.

If the soil was mixed exactly perfect for rammed earth walls, would that be enough? or is the lateral pressure too much?
If the inner walls were sloped at 84 degrees would that be enough protection? thats 1 ft more at the base of the wall than at 10 ft up the wall.
much more than that and it almost wouldn't work for interior walls.
 
Michael Cox
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Tom - you can use shallower slopes for structural walls but face them out with lightwieght stud work to get the interior surface.

I think in the Permaculture Designers Manual there was reference to large barns built in this manner. Raise the walls and level the interior with earth moving equipment and then just rest the roof frame over the top. I think it was mentioned as appropriate for areas with a fire risk for livestock shelter - the earth bank provides fireproof walls and structure. A metal frame roof.
 
Andrew Parker
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You ought to be able to find some engineering tables that would give you proper slope angles, given the makeup of your dirt, compaction and the height of the berm.

I don't really see why a sloped or terraced wall ought to be perceived as a negative.

I like the idea of a highly fire resistant structure, for man and beast.
 
Tom Harner
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Michael, about 3 hours before you mentioned the Permaculture Designers Manual references this topic, I purchased the book... I can't wait until it arrives... I know what I'm looking up first!

Andrew, sloped/terraced walls are not inherently negative, but they might be percieved as a negative, or have a negative relatioship with the other elements in the system (like my wife) thus causing negative effects to other elements (me).
Honestly though, its more about understanding the options than making decisions ahead of analysis. If everything else works out and the walls must have a significant slope then we would make the best of it.
 
Tom Harner
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YES!

I refound the Bill Mollison video where he describes this!
Direct link Start watching at 42:25 for this particular topic.

Here is a link to the rest of the video series.



**Updated direct link
 
Tom Harner
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"I'm positive your mother wouldn't like it."
 
Will Scoggins
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You could place a vertical studwall at the base of your slope and use the space behind wall at top for easy access behind your walls for storage or plumbing, electrical, HVAC, ethernet, etc.
 
Andrew Parker
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A sloped wall should be the least expensive option (no guarantees). If your wife would be happiest with conventional looking vertical walls, Micheal's suggestion is certainly viable, and there are many other options. Is this a thought experiment (no problem with me if it is), or are you making plans for an existing site? If you have a specific site in mind, some details would be helpful in narrowing down those options.
 
Tom Harner
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At this point in time, completely a thought experiment. We are saving to purchase land in the next 2-3 years. So I am feeling out posibilities in light of a very limited budget (probably in the thousands instead of tens of thousands). i.e. Do I want rugged land or flat? How quickly can we build and move? What tradeoffs will we need to decide on? etc.

My wife has tentatively agreed to this design as a possibility for temporary housing... just working through it.

And like I said, finding info on this is next to impossible. I have only ever heard of 2 structures build like this. Not to mention that it has the trifecta of warning signs: 1. it's quick, 2. it's easy, 3. it's cheap. Those four factors make me very leary... but one was built by Bill Mollison, the other by his student Geoff Lawton. These two are well respected for unconventionally achieving very positive results. Also, the design passes my "bull-shit-o-meter" and, like I said, I love the simplicity of the design; I just kinda speaks to me.

All that said, just because Bill, Geoff and I don't see the faults of the design doesn't mean they do not exist. (not that I'm in their league)
 
Michael Cox
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Well I imagine that if done poorly you could end up with a swimming pool in the living room.

Plus these designs are well suited to making a single large space cheaply - think a large barn/hangar. I'm not sure how comfortable they would be to turn into a home if you have inclement weather.
 
Tom Harner
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Why couldn't they be made comfortable? It wouldn't be any more dificult to finish than an earthship, or wofati, or cob, or... the only exception is that the exterior walls could be erected dirt cheap by one person with a dozer/excavator in a day. Roofing, glazing, plumbing, electric, finishing, etc, would all be silmilar to the above housing types. Correct me if I am wrong.
 
Tom Harner
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But yes ending up with a swimmingpool in the living room is a significant risk... or potential benefit! I would think that significant drainage (inside and outside the walls) would be part of risk mitigation.
 
Michael Cox
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Tom Harner wrote:Why couldn't they be made comfortable? It wouldn't be any more dificult to finish than an earthship, or wofati, or cob, or... the only exception is that the exterior walls could be erected dirt cheap by one person with a dozer/excavator in a day. Roofing, glazing, plumbing, electric, finishing, etc, would all be silmilar to the above housing types. Correct me if I am wrong.


The freaky cheap aspect of these structure is in their absolute simplicity. When you start trying to deck them out in a more sophisticated interior the cost of construction then becomes dominated by the interior fixings and the savings from the wall construction become proportionally less significant.
 
Tom Harner
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Michael Cox wrote:
The freaky cheap aspect of these structure is in their absolute simplicity. When you start trying to deck them out in a more sophisticated interior the cost of construction then becomes dominated by the interior fixings and the savings from the wall construction become proportionally less significant.


Is that less true of an earthship, cob or wofati?

I mean, I could build one big empty room using any of the above methods very cheaply (with much labor), but the more "comfortable" I make these buildings, the more expensive they become.
 
Peter Ellis
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It is essentially true of every mode of construction that the shell is the inexpensive part. When you start doing the interior finish work is where the money can pile up in a very big hurry. Just price the range for countertop materials

I think it would be ambitious to try to do four walls in one day for this kind of structure. And if I recall, I know the one Geoff was involved with and the client did not seem to want his hide-away being publicized very much, so it is rather to Geoff's credit that he honored that request, but gave us a clue about the idea.

 
Jesse Grimes
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I have been considering the ant village challenge, and this type of construction is on top of my list for the shelter. It could be built rather quickly with the excavator, or at least the walls could, without having to peel a ton of logs and set in a lot of big posts just to hold the roof up. I spent some time on the lab last summer helping with wofati 0.8, and one of my impressions was that it takes an awful lot of logs just to build the walls up. I spent a fair amount of my time there peeling logs, and it seems to me that just peeling enough logs by myself to build a 10x10 wofati would take about a month.

One downside of the design is the need to slope the interior walls, which effectively diminishes floor space while expanding the span of the roof beams. One thought is to do a kind of half Ohler, half earth berm design where you would build post and shoring walls on the bottom half of the slope, leaving the top half as a slope. So you would be supporting the bottom of the Earth berm where most of the lateral forces exist, while carving out a bit more interior floor space. You could even extend the posts up to act as secondary support for the roof beams, shortening the span.

Here's a quick ms-paint sketch: (anyone know where I can get sketch-up, and a good tutorial?)

Its a front elevation. The left side shows the post going all the way to the roof, the right side only to the top of the shoring.

Looking at it now it seems a lot like and Ohler structure with all that shoring, except you only have to cut half as much shoring boards, and the roof isn't really supported by the posts so much as the earth berm.


Another idea is that much of the floor space inside the house will be taken up by the bed (I like a big bed), so why not fill the back half of the interior with an earthen platform 3 to 4 feet high, and just make that the bed. It would provide lateral support to the earth berms along the entire back wall, and half of the side walls. This would cut down on the needed shoring a lot, you might not even need to shore the front of the bed platform. Even better, you could make the whole bed platform into the mass for a rocket mass heater. You would have to isolate it from the earth berms and the earth beneath it with rigid insulation, but it would still serve as shoring for the berms. Can the rigid foam insulation take the lateral pressure without being crushed? I'm thinking it can since it is used along the back wall of earthships and the like, where it is covered by tons of dirt.

Here's another quick sketch:

The pink is the insulation, and the berm closest to the viewer has been removed to show cut-outs, and how the rigid insulation would be installed around and under the mass. None of the heating ducts or anything else are shown.

I thinking in time the whole thing would be covered with an insulation/watershed umbrella and a greenhouse built on the front, but to start with the rocket mass heater bed and 12 foot thick walls should keep it nice and toasty come wintertime. What do you all think? Is there something I'm missing? I worked in the underground utility field, so I am well aware of the dangers of being crushed by tons of dirt, I want to makes sure I get this right.
 
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