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Reinforced Cob Walls

Posts: 58
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I know this may be a crazy question or idea in general. Plus it would be really expensive but I'm asking our of 1 curiosity and 2 for my lovely wife who has anxiety.

So here goes

We are still in the planning phases of how we would like to build our cob house. We have both agreed we would like to have the house to be somewhat of a fortress.

In doing so we have decided that bullet proof windows, heavy iron doors, and much more would be preferable.

But what we were wondering is it plausible (excusing cost) to put 3/4 inch steel into the core of a cob building and place the cob around it.

Yes we are aware that this would take away from the breathability of the cob but it something we are just curious about. Also any really strong alternative ideas would be great as well.

Also let me clarify why we are asking.

As stated my wife has anxiety and it is especially bad at night.

She is terrified of what happens if:
•We get shot at (the house we are in has been randomly shot at many times even though we are openly visible)
•someone tries to break in
•someone sets off a bomb/grenade (this is where the question comes from)
•a fire happens
•tornadoes (this is a big one we haven't gotten to planning yet)
•and sooooooo many more.

Anyway, thanks in advance for all the answers to come, and please have fun with your answers.
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Location: Abkhazia · Cfa (humid subtropical) - temperate · clay soil
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Richard, apart from suggesting to relocate out of a war zone…

Rammed earth should work, the question is just how thick.
Everything else depends on how much space you have…
· a high wall around the house would stop bullets before they get to the window and also stop a fire,
· going underground would make it tornado and fire proof.
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Location: Massachusetts, Zone:6/7, AHS:4, Rainfall:48in even Soil:SandyLoam pH6 Flat
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After being randomly shot at multiple times, I would have anxiety just like your wife. I sympathize with her.

Concrete/Cement Roof help with tornado/bullet/bomb.
Bermed with soil on 3 sides also help.

You could really just live underground in a 1500sqft house and have a little 400sqft shack on top that leads to the underground/real/basement house.
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Location: Toronto, Ontario
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That would be interesting. I would make sure that you have enough insulation on the outside of your thermal mass to prevent cooling and condensation issues.

I don't think that a steel core is necessary. I have heard, especially for earthquake-prone areas, that layering the packed stabilised earth mass, in the case of rammed earth, in lateral layers with reinforcing tie-in layering (I think landscape fabric is used, conventionally) is preferable, but those measures would easily handle conventional munitions.

I would consider perhaps an in-ground, ground-coupled dwelling, with exaggerated berms on all sides up to a reinforced green roof that, from a distance, might obscure the presence of a house entirely, and functionally would put two to three feet of soil between the house walls and the exterior.

Also, depending on what form your build takes, you could construct your building with an interior garden courtyard, with a reinforced outer wall and windows more functional as ventilation and shooting than access and view. If that were combined with bermed outer walls, your building, save for outward-facing slits and doors, would appear as a rise in the landscape, nothing more, and could easily be obscured from overhead by a low-branching thick tree canopy.

Cob in this context is more a plaster finish than it is a construction material.

I hope the advice you find here is helpful to you. Please keep us posted, and good luck.

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Here are some ideas I've been contemplating and information sources I've been learning from.  

While researching ancient buildings that endured various natural disasters for many centuries and remain intact, what appeals to me most so far are thick adobe, stone, or cob walls (suitability depends on area and intended use) with basalt reinforcements to create stabilized earthen walls.  Thick walls of course will require much more intensive labor and time, but I feel the end result will be worthwhile.  

Most of my ideas have no less than 3' thick walls, and I am inclined toward domes (360 degree arch support) with 5' thick walls at the foundation that decrease to about 3' at the roof - all of which will be reinforced with stabilized earth using basalt fabric about every foot from within the foundation to the top.  The idea is if a freak gust of wind drops a large tree on the top, little to nothing happens.  As ideas firm up, I'll be asking for help to determine an optimal distance between layers of basalt fabric in layers of cob (my choice so far).  

I feel high, narrow, dormer-type windows are important and I've chosen hurricane glass.  The walls will be thick enough that the dormers can be inset to prevent wind, rain, and snow from reaching the glass.  And the outer area around the dormer windows will be shaped to direct rain and snow most appropriately.

To disturb the ground as little as possible, I am thinking of building a small shelter in ground, then building the rest of the home upward and surrounded by terracing and hugelkulturs as protection from wind, to both draw moisture away from the home while utilizing snow and rain for the food forest planned on and around the hugelkulturs, and for privacy.  (The earthworks come first and the land determines those, however I need to have an idea of what the home is about to plan around it.)  (Also planning a large-ish pond as water source, a way to bring water into the home what is not easily detectable from outside, and perhaps a separate small, sealed saltwater pond to create electricity without being on a short leash with solar.)

So far I am avoiding certain cements because breathability is a must to remain healthy and not create a sick building.  I am still studying breathable plasters and ways to protect a roof and walls from moisture.

While I don't perceive myself to be a prepper, I do have immense respect for the elements and nature's curveballs.  I also figure staying safe requires choosing an area in which the worst of human nature is most likely avoidable.  That said, to satisfy curiosity about weathering stray bullets from hunters, I found some youtube videos that demonstrated what kind of bullets go how deep in various materials and wall thickness.  I would post those links, but considerations most likely vary with individual concerns.

There are numerous other considerations, but this post is most focused on feeling safe and avoiding natural and human-related catastrophes.

Here's are some information sources I've researched specific to basalt rebar / rope / mesh / fabric.  A few months ago the pricing seemed reasonable, while stronger and less expensive than steel, more environmentally friendly, and does not attract condensation as metal does because basalt is glass.  Here are some links and permies posts that helped me begin exploring options.  








Richard Force
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Catherine Windrose wrote:  (Also planning a large-ish pond as water source, a way to bring water into the home what is not easily detectable from outside, and perhaps a separate small, sealed saltwater pond to create electricity without being on a short leash with solar.)

I've never heard of doing something like this for electric before and it now has me highly interested.
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Location: Ontario - Gardening in zone 3b, 4b, or 6b, depending on the day
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Yikes, I'd be scared too! Where in the world do you live?

Have you considered earth bag? It's developed from how military temporary fortifications are typically constructed (sand bags) + steel reinforcements, and then plastered on the top. You'd get the "look" of cob, with more strength and some peace of mind.
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It seems like it would be perfectly feasible, minus the whole money part.  You might want to look into galvanic protection to handle corrosion.  You can use sacrificial paints as well as anodes connected to a good conductor, like moist subsoil, to make a steel structure last pretty much indefinitely.

Breathability depends mainly on surface exposure, so if you could provide ventilation for the core of the wall, for instance unlined ducts molded into the cob with some provision to ensure air exchange, it should theoretically be possible to keep it dry, even passively, by moving the exchange site from the covered face to a network of interior surfaces near that face.  An inlet and outlet would be necessary of course.  It might be possible to stimulate the airflow with a solar chimney, too.  It wouldn't be a bad idea to embed some moisture sensors to keep an eye on it, just to be safe.  This would definitely interfere with the thermal properties of the wall, too.  Probably.  Definitely.  Maybe.

For breathability all the way from one side to the other, it's really more of a side benefit of cob than anything because there are half a million ways to achieve ventilation that don't require cob.  If the ducts for exhausting moisture can be designed to function equally well for ventilation, that's just icing on the cake!

Steel being what it is, you would need to add a good mechanical attachment method to the plates of steel.  Rebar tack-welded to either face comes to mind as a fairly conventional solution.

As far as cob as a material goes, I think it has so much more potential than current methods provide.  Because it is so cheap you can make it as thick as you want, and wind up with ample structural capacity to boot.  It would certainly be far cheaper to provide more roof to cover a thicker cob wall than to embed 3/4" steel plate, and you would have the year-round temperature regulation of a berm without the moisture considerations.  The wall could rest on a pad of stone, gravel, or concrete and be inherently stable against frost heave.  You could have fancy built-in nooks with your windows without significantly weakening them.  You could have secret passages in the walls, and offset trick mirror windows, and deep candle-lit relief sculptures, and, and...
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Location: Bendigo , Australia
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Maybe a bit of thought about random shooters.
I dont think I have heard of such activity before.
So there may be a solution.
Otherwise, the underground options would be something to think about.
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Location: OK High Plains Prairie, 23" rain avg
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Unless you have no choice but to live in a war zone, I would suggest a reasonable alternative before building a fortress to your wife's anxiety. There are many successful therapies to deal with anxiety and even PTSD. EMDR, eye movement desensitization, and other therapies can alleviate much of the trauma response that causes us to want to over protect ourselves and our loved ones. Therapy is cheaper than a steel- reinforced house and frees us up to enjoy life. All my best to your beloved.
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Sounds like your planning for "the end of all days".

I've seen videos online where people shoot into boxes of dirt with different calibers of rifle and handgun, including guns that are as powerful as you are likely to meet outside of africa.  None make it deeper than 9 inches (these are jacketed, but not armored rounds).  From this, I think a foot of rammed earth/ dirt or adobe will stop pretty much anything short of a 50 caliber machine gun.  Depending on the amount of straw in your cob, you can make it heavier or lighter.  If you put cob on the outside you would have a massive heat reservoir inside you house, making cooling/heating easier.  

Hope this helps.

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