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Stone facing for rammed earth retaining wall  RSS feed

 
Woo Nin
Posts: 1
Location: MN, USA
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I am looking for some help with planning the facing wall of a house that I am building.

The house is built into the side of a hill, with one side of the basement level opening out into the downhill side, as a tuck-under garage. The wall for this side of the garage is poured concrete, about 11 feet high.

I want to finish the outside surface of this wall with a battered stone face that mimics the stone facing of the rammed earth walls that are typical for the earthen works of Japanese castles, so it appears that the living level of the house stands on an earthen rampart.

I think the location where I am (western WI) has soil with a clay content that will be suitable for rammed earth. There is also an abundance of limestone, fractured into slabs, that resulted from excavating the foundation into the hillside. I would like to make a battered rammed earth wall on the outer surface of the poured concrete wall, for the full 11' height, using the concrete wall as the back side of the form.

Would I be able to use the limestone slabs recovered from the site as a facing for the exterior surface of the rammed earth wall? Ideally I would like to line the front side of the form with them, compact the earth/cement mixture against the inside surface of the slabs, then remove the forms and display the outer surface of the slabs as the facing of the wall.

Is there too big a risk that facing slabs will not be stable over time? There is a poured concrete footing under the entire area where the rammed earth wall will stand, which extends down past the frost line in my area (42").

Any help or advice that you guys can give would be welcome. I would like to build something more authentic than a stone facing over wood framing.

 
Dave Turpin
Posts: 112
Location: Groton, CT
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Are you just going for the look or are you looking for more thermal mass in the house?

The simplest solution for the look would be to anchor mesh to the concrete using concrete screws, then affix the stone facing using mortar. Special mortaring techniques are required for big stones, though.

If you wanted a 11' tall rammed earth berm... Well, that is an engineering challenge and I am afraid it would be prohibitively expensive.
 
Bill Bradbury
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Posts: 684
Location: Richmond, Utah
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Hi Woo,

Stone facing with flagstones is typically a veneer, but for an authentic look, I think you are after a stone wall. This can be built by excavating down to the footer, adding a gravel drainage and bedding layer and building up a stone wall with lime mortar and galvanized brick ties attached to the basement wall.

I recommend Ian Cramb's books on stone masonry to help you with the details.

https://www.google.com/search?client=safari&rls=en&q=random+rubble+masonry&ie=UTF-8&oe=UTF-8

All Blessings,
Bill
 
Jay C. White Cloud
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Hello Woo,

I think I have a grasp of what your goals are, but feel free to correct me if I have missed any points, or questions.

I want to finish the outside surface of this wall with a battered stone face that mimics the stone facing of the rammed earth walls that are typical for the earthen works of Japanese castles, so it appears that the living level of the house stands on an earthen rampart.


I think here there may be some confusion and perhaps misunderstanding in how these 城 (Shiro-"Castle") are built in Japan. Though some of the earlier forms may be more similar to a 土塀 (Dobei -Earthen wall) or 土壁 (Doheki -clay wall) . Unlike China's, "Great Wall" which does have rubble or rammed earth core in sections of the wall, most 城 (Shiro) aren't constructed quite this way. I should also point out that even the RE of China has many different elements and methods to it from "rice soup," blood, fiber and other strengtheners to include lime also as one of these agent. 城 (Shiro) are not even built like 土蔵 (Dozō-soil warehouse) and the stone is anything but a "veneer" or facing of stone. These 城 (Shiro) are built more to the manner that Bill has reflected upon and actual 石垣 (Ishigaki-stone walls) are very solid and built with well fitted large stones. They are not constructed as a "stone facing" and would not survive the heavily active tectonic geology of Japan, if built in such a fashion.

The "earth rampart" is called a 基壇 Kindan or the “podii” (壇上積 danjouzumi - dais) of raised stone and earth does forms a platform in many Asian architectural types from the Middle East through India, China, Korea, and into Japan. This is very distinct in design and is broken down into several basic elemental forms. 版築 (hanchiku-rammed earth) can be part of "some" of these earlier forms of castle, but are not built as described in this post intent.

I think the location where I am (western WI) has soil with a clay content that will be suitable for rammed earth. There is also an abundance of limestone, fractured into slabs, that resulted from excavating the foundation into the hillside. I would like to make a battered rammed earth wall on the outer surface of the poured concrete wall, for the full 11' height, using the concrete wall as the back side of the form.


I would need to see photo of the building site, and understand the current architecture better to give any reasonable (and safe) guidance to such modifications. Adding so much "hanchiku" to a structures and then stone too is probably not advisable.

Would I be able to use the limestone slabs recovered from the site as a facing for the exterior surface of the rammed earth wall? Ideally I would like to line the front side of the form with them, compact the earth/cement mixture against the inside surface of the slabs, then remove the forms and display the outer surface of the slabs as the facing of the wall.


I would have to see the stones, and understand the "dry laid" and stone carving/fitting skills of the person seeking to achieve such a facade on a building.

Is there too big a risk that facing slabs will not be stable over time? There is a poured concrete footing under the entire area where the rammed earth wall will stand, which extends down past the frost line in my area (42").


I am of the thought currently that this probably needs to be "re-thought" as a project. Rammed earth (hanchiku) really isn't part of this system of building, and definitely not as described in this "make over." Even the concept of "frost heave" in most building codes is a misnomer and poorly understood. Forest heave doesn't even take place as much as "clay-water expansion" which can be 10 times more disruptive and destructive than just expanding ice alone. If water is "properly" manged and drained away from a building site "frost heave" can't take place, and there is not water present to catalyze the action.

Regards,

j
 
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