Sustainable building with earth, corrugated galvanised iron and rebars

[Blokle]

TL;DR Summary

House building idea: earth filled walls made of corrugated galvanised iron and reinforcing bars

There are lot of people on the Internet trying to build a cheap and sustainable house. Inspired by them I came with the idea of building external walls of Corrugated galvanised iron (CGI) and rebars and fill them with earth / sand. The basic element of the wall structure is this rebar trapeze with hooks on the inner side:

Both its legs are placed fully into the ground up to the horizontal bottom bar (base). The above the ground height of the trapeze is 3 meter, the base - 1m and the top 0.5m Many such trapezes are placed at the perimeter of the future house and welded together into the following structure:

Next CGI sheets are perforated and hanged on both sides of the trapezes (on the inner hooks) starting from the bottom. Once they are filled with earth, next level of CGI sheets is added upon the lower level and also filled. During the filling, once the earth reaches their level - opposite hooks can be connected with metal wire to reduce chances of trapeze deformation. And so on until everything is filled up. Inner space can be divided into rooms using metal rods and drywall (gypsum panels). Ceiling and the roof will be supported by a separate metal rods structure of appropriate size. Some of those metal rods might be buried inside the earth of the walls. Now my primary questions...

1. Do you think such a construction is stable enough (on its own and in case of an earthquake)? If not, how long should the base and the top be, if the height should stay 3m?
2. What kind of rebars - radius, type, etc. should I use in such a case?

There are also some secondary questions, but they are less important...

3. Should I try to hermetically seal the holes of the CGI sheets or will the rainwater drain through the inner filling further to the ground?
4. What kind of ceiling would you recommend? The material should provide good thermal insulation (preferably also acoustic, be inflammable and not cause health problems).
5. How would you recommend to seal the connection between CGI sheets on the bottom and the ground?
6. What kind of CGI sheets would you recommend for the walls and which for the roof? (at the end the structure should be as cheap as possible, but not cheaper - safety first!)

 

[phinds]

Windows?

 

[Blokle]

Windows? And doors... - metal frames inside the walls that will hold the earth above it and on the sides. Interesting point regarding windows - should I cover the bottom part (the "windowsill")? I would prefer the earth to be exposed on the windowsill, so I can plant flowers there directly without a planter. On the other hand I don't know how the earth will behave there... will it be pressed out by the upper layers (like water would have), or not?...

 

[Baluncore]

Rebar with corrugated iron, will not survive in contact with soil. The hidden rebar will rust away and be gone, before you realise why you were crushed by the falling structure.

Build the walls from used tires, each with the upper sidewall cut out with a sharp knife. Stack a layer of tires like blocks. Screw the tires together vertically and horizontally with galvanised screws. Fill each layer with soil, then compact. Overlap and repeat. Paint the tire walls white to insulate.

Make the roof from corrugated iron, screwed to timber beams.

 

[jack action]

The galvanized steel sheets will rust. It takes a longer time but you will get holes from the humid earth within decades at most. Galvanized steel is not considered a cheap material either.

What would be the advantages compared to rammed earth houses?

 

[Baluncore]

Keep galvanised iron away from soil, it is designed to chemically react, which is why it is covered in expensive zinc.

Galvanised iron is good for roofs, because it weighs the least of all durable roofing per unit area. The water that runs off, can be used. Galvanised iron can hold the walls upright during earthquakes.

Tiles and slate roofs are very heavy, so require strong support and walls. People are killed by falling tiles.

Tiled roofs get blown apart during windstorms, and allow embers to enter the roof-space during bushfires.

Following a firestorm that entered a Canberra suburb, the houses that burned down had tile roofs, those with galvanised iron survived.

 

[Blokle]

Rebar with corrugated iron, will not survive in contact with soil.

Right. That's why I wanted to paint all rebars and the inner part of the CGI sheets with tar / resin.

The hidden rebar will rust away and be gone, before you realise why you were crushed by the falling structure.

I thought the trapeze barrier were stable enough even without the legs in the ground...

Build the walls from used tires, each with the upper sidewall cut out with a sharp knife. Stack a layer of tires like blocks. Screw the tires together vertically and horizontally with galvanised screws. Fill each layer with soil, then compact. Overlap and repeat. Paint the tire walls white to insulate.

Tires are known to be not healthy. Reusing them is forbidden in some countries. And filling each of them with soil is labor intensive...

 

[Blokle]

The galvanized steel sheets will rust.

Yes. I plan to paint them with resin / tar.

What would be the advantages compared to rammed earth houses?

Those are labor intensive and time consuming - you need to wet the soil, compact it, let it dry. And this for each several bricks. In my case you just fill the walls (maybe even with a small excavator) and that's it. You don't really need to compact it too much (or at all), since even if the soil will sink with the time 20-30 cm - it will neither be noticeable from outside nor will it have negative impact on the stability of the structure. You'll be able to add soil with the time. Another advantage - the soil is not exposed to the rain, wind, sun... Those rammed earth houses do not hold in their original shape for too long...

 

[Blokle]

Keep galvanised iron away from soil, it is designed to chemically react, which is why it is covered in expensive zinc.

As I said I plan to cover them additionaly with resin / tar - can this damage the zinc layer?

Galvanised iron can hold the walls upright during earthquakes.

Do you mean that galvanized iron can hold the walls upright during earthquakes in my approach or in general?

 

[Baluncore]

Do you mean that galvanized iron can hold the walls upright during earthquakes in my approach or in general?

I mean a well attached light-weight galvanised iron roof can prevent the walls from falling.

Tires are known to be not healthy. Reusing them is forbidden in some countries. And filling each of them with soil is labor intensive...

Packing soil between two sheets of galv, will be more difficult than filling a course of tires, as it is laid. The reo will obstruct filling and compaction. You will damage tools, and cut your hands and arms, while reaching into the wall, over the iron.

Used tires are only unhealthy if they fill with water and breed mosquitoes, or catch fire. Bitumen and tar are known carcinogens. Used car tires have lost most of the volatile organics, so are safer.

 

[Lnewqban]

Would you consider replacing the structure of steel bars with a light gauge steel one?
In order to reduce cost of materials and specialized labor, rather than welding, you could screw all the structural links to each other, and then the corrugated sheet metal panels onto them.

If so, please, see:
https://lbcc.pressbooks.pub/buildingconstruction/chapter/84/

I would start by consulting the current restrictions and construction codes in your jurisdiction, especially regarding wind loads and fire protection.

Best luck with your interesting idea and potential project.

 

[Vanadium 50]

Windows?

I think he may use a Mac.

Seriously, I agree that galvanized steel will rust. It lasts...until it doesn't. Once the rest penetrates the protective layer, the degradation goes very, very quickly.

 

[phinds]

I think he may use a Mac.

Yeah, he's probably an Apple guy, but I think he'll realize that his design is going to need windows.

 

[Rive]

Water insulation will be a nightmare.
Heat insulation is impractical.
Connecting it to any other building material - roof? - almost impossible.
Long term the fill will change sizes.

Just - nope. There are lot less troublesome alternatives.

you just fill the walls (maybe even with a small excavator) and that's it.

Then why not just pack some shipping containers and bury them?

 

[Baluncore]

Then why not just pack some shipping containers and bury them?

Because the wall pressure rating of a shipping container, is less than the hydrostatic pressure of the soil.

Shipping containers are designed to stack and support loads vertically, not to be squeezed by wet soil. Shipping containers require a concrete retaining wall, and a water barrier.

If a container is buried, so it can be driven over by a vehicle, then it also needs a reinforced concrete or steel cover.

 

[Nik_2213]

Like timber, re-bar and sheet must be isolated from ground-contact. Hence eg pergolas and decking often have concrete footings and 'up-stands' to safely attach supported pillars and beams. Hence sheds / barns have a foot-wall, so their metal siding begins above splash-line.....

Perhaps not as crucial is danger of stray currents causing rapid electrolytic demolition of the metal. Steel towers, pipelines, Boats and ships resolve by using bonded 'grounds', sacrificial anodes and 'trickle' currents to be sure, to be sure.

Also, regarding the 'Bury a TEU', there are ample horror-stories to be found about incautiously buried TEUs caving in. There's excellent reason for eg buried gulleys, sewers and water-tanks to be cylindrical or arch-topped, historical tunnels arched, cellars vaulted etc etc.

A caution: There's a world of difference between 'Earth Sheltered' with a fully-load-bearing 'green roof', and simply burying a big, box whose strength lies in its edge framing, not the panels between...

Due Care, please ???

 

[Blokle]

Would you consider replacing the structure of steel bars with a light gauge steel one?
In order to reduce cost of materials and specialized labor, rather than welding, you could screw all the structural links to each other, and then the corrugated sheet metal panels onto them.

If so, please, see:
https://lbcc.pressbooks.pub/buildingconstruction/chapter/84/

I would start by consulting the current restrictions and construction codes in your jurisdiction, especially regarding wind loads and fire protection.

Best luck with your interesting idea and potential project.

Do you mean to replace rebars with light gauge steel and make the trapeze like barrier using them? Are they cheaper than rebars?

I actually wanted to use them to bear the ceiling/roof by burying them into the walls like in the picture bellow.

I've heard many interesting remarks so far, but nobody had answered my primary question - is this structure stable? Earthquake stable?...

 

[Blokle]

Water insulation will be a nightmare.

Why? I"ll cover inner facing planes of the sheets with resin / tar. Roof will hang over the walls, so no rain water will drop from above onto the top of the wall. The bottom part of the barrier, touching the ground, can be sealed with concrete.

Heat insulation is impractical.

If the ceiling / roof is well thermally insulated the significant thermal mass of the earth in the walls might make the inner temperature quite pleasant and stable even without an air conditioner.

Connecting it to any other building material - roof? - almost impossible.

See my previous post where I show how to attach a roof (without putting any load on the walls).

Long term the fill will change sizes.

So what? 1. I can always add more earth once it gets compacted on its own inside. 2. I actually don't care - nobody sees what happens in the walls and since it bears no load - it will not deform due to new empty space that has appeared...

 

[Blokle]

Yeah, he's probably an Apple guy, but I think he'll realize that his design is going to need windows.

I'm actually a Linux guy... so I've covered the windows and doors issue in advance...

 

[Baluncore]

@Blokle
Attacking and dismissing every suggestion, as soon as it is presented, is not a wise strategy. You need to consider the alternatives being presented more carefully.

You seem to be reacting immediately and emotionally, with prejudice. If you are not willing to take on, and fairly evaluate the suggestions presented, they will cease to be presented.

 

[Lnewqban]

Do you mean to replace rebars with light gauge steel and make the trapeze like barrier using them? Are they cheaper than rebars?

Yes and yes.
Besides, they have flat surfaces onto which attach your corrugated panels using self-tapping screws.

... nobody had answered my primary question - is this structure stable? Earthquake stable?...

Not as originally presented.
Shear loads must be counter-acted by diagonal bracing on the three planes (which is also easier to do with screws than welding).

Just imaging that each corner in your diagram, where two bars meet, gives those certain freedom to rotate respect to each other under wind and ground forces.

Please, see:
https://www.carportcentral.com/blog/wall-bracing-work-metal-buildings

 

[Rive]

:sigh:
Goin' the usual way
We have around 20% of homes here still with variations of 'mud' in them.
We even have a cult around them.
We have abundant experience about all the benefits and drawbacks.
Especially about the drawbacks.
Still, once it goes 'culting' nobody listens.

Why? I"ll cover inner facing planes of the sheets with resin / tar. Roof will hang over the walls, so no rain water will drop from above onto the top of the wall. The bottom part of the barrier, touching the ground, can be sealed with concrete.

What you describe there is more or less about a water- and airtight enclosure around a non-load-bearing gigantic pile of mud of very inconvenient shape.

By the time it's properly done for that price you could use proper and simple load bearing, insulating material.

If the ceiling / roof is well thermally insulated the significant thermal mass of the earth in the walls might make the inner temperature quite pleasant and stable even without an air conditioner.

Mud walls in specific environments has such climate effect.
That is, when it is in connection with the inside, without any moisture barrier like metal sheet or such.
Even a thin layer of plastic paint might ruin the thing, since it's mostly about the control of internal moisture levels.
Given that the thermal insulation of those walls is really not something to brag about, the effect of the thermal mass alone is quite controversial.

See my previous post where I show how to attach a roof (without putting any load on the walls).

We have really deep experiences about how is it possible to mix the stuff with other materials.
In general, it's not working very well.

So what?

So nothing. If it decides to expand you won't hold it back with that puny sheet of metal. 'Can tear apart reinforced concrete.


With all that effort maybe you should consider hay bales as filler material. Lot better, still cheap and common, bends well with wood and drywall.
Can be made decently fire-resistant too.

 

[Blokle]

@Blokle
Attacking and dismissing every suggestion, as soon as it is presented, is not a wise strategy. You need to consider the alternatives being presented more carefully.

You seem to be reacting immediately and emotionally, with prejudice. If you are not willing to take on, and fairly evaluate the suggestions presented, they will cease to be presented.

I'm sorry if I've sounded aggressively. It was not my intention. I'm actually interested in people pointing out to possible weak spots in this design. This will help me to improve it. Or indeed drop it altogether if it's that bad. I just try to defend this idea and hope the truth will be born out of this discussion :-)

 

[Blokle]

Still, once it goes 'culting' nobody listens.

So far there is no cult around bizarre trapeze-like walls :-) who knows - maybe there will be one day :-)

By the time it's properly done for that price you could use proper and simple load bearing, insulating material.

Well, there are two requirements on the walls that I've not mentioned explicitly, but which brought me to that choice. Namely, my walls need to be inflammable and bullet-proof. So if you can suggest other alternatives that meet these requirements - I'll be happy to hear.

Mud walls in specific environments has such climate effect.
That is, when it is in connection with the inside, without any moisture barrier like metal sheet or such.
Even a thin layer of plastic paint might ruin the thing, since it's mostly about the control of internal moisture levels.
Given that the thermal insulation of those walls is really not something to brag about, the effect of the thermal mass alone is quite controversial.

Interesting. I thought it were all about the temperature that remains stable due to high thermal mass (no matter what material). And once it's cool, so there is less moisture in the air. You say that the moisture is removed by direct contact with mud. I don't know the subject well enough to argue here...

With all that effort maybe you should consider hay bales as filler material. Lot better, still cheap and common, bends well with wood and drywall.
Can be made decently fire-resistant too.

Hay bales as filler material? What can I fill with it so it can be done fast and easy?

 

[Baluncore]

Hay bales as filler material? What can I fill with it so it can be done fast and easy?

Straw bales are now a traditional building style. You do not fill anything, because filling things is difficult.
The bales are laid like big bricks, thin wooden stakes are hammered in vertically as the process continues. The stakes are held together by fencing wire between layers. Once a wall is built, the surface is profiled gently, with a chainsaw. A chicken-wire mesh is then placed on the inside and outside, the two being stitched or pulled together by fencing wire, that passes through the bales. That is then rendered with mud, inside and out. No hay is exposed.
Straw bale houses are quiet, and have thick insulated walls. The roofs have wide eves, that keep the sun and rain off the walls.
https://en.wikipedia.org/wiki/Straw-bale_construction

 

[Baluncore]

Rebar without concrete is not sensible. It will pull easily from the ground and bend, or it will cut through the packed earth in the wall. Rebar is only good for tension, when held in place by concrete. Rebar is its own neutral axis, you could do better using hollow iron pipe, that has a greater diameter for the same weight.

There are ground anchors used in vineyards, that are hammered deep into the soil before tension is applied to the attached anchor wire, that toggles the anchor, and locks the anchor into the ground. Those anchors will stop your walls blowing away.

A freestanding wall that will survive wind and earthquakes has only short straight segments. It has many sidewalls that separate the internal space, or it is built as a zigzag or sinusoidal wall. That widens the base of the wall, without needing so much material. Those walls are good for cold climate gardens, where they store heat from sunlight.
https://en.wikipedia.org/wiki/Crinkle_crankle_wall

 

[Rive]

Straw bales are now a traditional building style.

There is a variation when a self-supporting timber frame is filled up with bales. Maybe a bit more modern-ish.

my walls need to be inflammable and bullet-proof.

Regarding the former, straw or hay bales are actually surprisingly good.
Regarding the former, piled dirt is not considered reliably bullet-resistant. Compacting, but rather: bagging and layering is recommended. And with that you are back to the good old earthbag constructions. No complicated and non-sustainable metal parts needed.

...but I feel that the topic is fast delving towards rabbit holes of for zombie apocalypses.

 

[Baluncore]

There is a variation when a self-supporting timber frame is filled up with bales. Maybe a bit more modern-ish.

Yes. In some places the building code requires structure, beyond vertical stakes, to support the roof, and a structure is certainly needed by little piggies for multi-storey straw bale construction.
https://en.wikipedia.org/wiki/The_Three_Little_Pigs

Basalt can be made into rock wool, then used for insulation, and now rebar and mesh. The rebar is stronger and lighter than steel, and does not rust, so can be close to the surface of concrete. It cannot be bent like steel, but is cut and can be joined and held in place with cable ties, before concrete is poured.
https://www.newcivilengineer.com/in...el-in-infrastructure-construction-09-05-2023/

Stopping bullets is more difficult. Straw bales have too low a density, so will need armour plate, but there is a more interesting way. Clad your structure in Plastic Protection, that is chips of granite, embedded in bitumen. The bullets tend to fragment against the matrix, and the impact does not spawl material inside. Bitumen is a fire hazard, so Bokle would require an external fireproof shield.
https://en.wikipedia.org/wiki/Plastic_armour

 

[jrmichler]

The galvanized steel sheets will rust.

Which is why I spent yesterday afternoon in a meeting with a commercial loan officer to arrange bridge financing (short term loan) to pay for a concrete bridge to replace a rusted out 10 foot diameter galvanized steel culvert. That culvert lasted 40 years, which is about average for galvanized steel culverts. The situation was made more interesting when the contractor started work a full month earlier than initially promised, plus I just got the job (town board chair) two weeks ago. Learning curve combined with tight deadline is always fun.

 

[Blokle]

Following your feedbacks I decided to switch to the following:

1. use light gauge steel to build the structure for the walls and the roof.
2. use sheet metal SIPs ( https://en.wikipedia.org/wiki/Structural_insulated_panel ) for the walls themselves.
3. surround the walls with big bags ( https://en.wikipedia.org/wiki/Flexible_intermediate_bulk_container ) filled with earth and stacked one upon another (3 layers), optionally interlocked with barbed-wire to hold all this together. On the inner side the bags will be stocked straight and touch the SIPs; on the external side they will be tilted a bit (by e.g. using bags with decreasing width on each subsequent upper layer) - like in the picture below. Plants can be planted into the bags walls.

What do you think about this idea? The bags with earth can obviously make the house bullet-proof and inflammable (more or less), but what about the internal temperature? Will the thermal mass be enough to keep the temperature within 20-26C without heating/cooling in mediterranean climate?

Any cons to this design?


Inspired by this:

 

[Baluncore]

The bags with earth can obviously make the house bullet-proof and inflammable (more or less), but what about the internal temperature?

How long do polymer bags survive in the environment? What happens when poly-bags burn during a grass-fire, or become water-saturated, and burst?

Avoid the word "inflammable" it is confusing and misunderstood.

 

[Vanadium 50]

Avoid the word "inflammable" it is confusing and misunderstood.

Agreed.
Non-inflammable is even more confusing.

 

[Blokle]

How long do polymer bags survive in the environment? What happens when poly-bags burn during a grass-fire, or become water-saturated, and burst?

Avoid the word "inflammable" it is confusing and misunderstood.

If not exposed to direct sun light I think the bags can survive 10 years or more. So planting something in them can be both decorative and protect them from sun. Another way to protect them is with mud. Also from fire. Make holes in the bottom and water will go out... But what does your intuition tells you regarding the inner temperatures and the thermal mass of all this?

 

[Rive]

planting something in them

That's a taboo. For any earth- (mud, clay) based construction water and plants are bad news. It is even a rule of thumb in the business that any aggressive/invasive root-propagated plants: grapevine, ivy, bamboo, japanese knotweed and such) are to be kept several meters away, and on the walls nothing is allowed what might grow roots or grabs into the wall for support.

Another way to protect them is with mud.

That's the traditional way. Requires frequent attention, but really low cost.

Make holes in the bottom and water will go out...

You need to prevent it going in ... Roof and insulation at the base: also the right placement/environment.

Will the thermal mass be enough to keep the temperature within 20-26C without heating/cooling in mediterranean climate?

It is moisture 'management' what makes the trick, and with (plastic?) bags involved that's not trivial. But with the right materials it is possible. You need to connect the inner (mud) plaster to the main mass of the wall somehow, without any moisture barrier. Think about some non-plastic bags

 

[Baluncore]

If not exposed to direct sun light I think the bags can survive 10 years or more.

The use of polymer bags, is not in any way sustainable.
That they will only last about 10 years, makes it doubly so.

The thread title: "Sustainable building with earth, corrugated galvanised iron and rebars" is a contradiction of terms. To be sustainable, you must avoid all plastics and iron.
Mud bricks, made with straw, do not need reinforcing steel, nor galvanised iron.

If you have windows and doors, bulletproof walls will not save you. If you must build fortifications, you are over-investing, or building in the wrong place.