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Comment by beAbU | Hacker News Reader

I did not watch the whole video, but...

The video talks about "no cost at all", except it ignores the massive amount of labour and time required to hand make bricks from mud and go from there.

Later on the video talks about ancient structures (pyramids, great wall, etc) that withstood the test of time, ignoring the MASSIVE human cost associated with building those things. How many people died housing a small handful of elites? In what living accommodations did thoses slaves find themselves?

I can guarantee you that if ancient pharoahs had access to glass and concrete they would have used it. Especially if it made it cheaper or quicker to build what they wanted.

How do you house the population on this planet without making use of cheap to produce, scalable and durable materials such as steel or concrete?

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The video makes the point that a single bag of cement costs €20 in an area where the average daily wage is €10.

I bet peaches are expensive in that area too, because there are no peach trees.

Concrete costs about $160 USD per cubic meter both in the USA and in Zaire (first African country I cound find a price), that works out to $4 USD a 35 kg bag, but in this case it's mixed and ready to pour.

If concrete factories were more common there there, I'm sure the price would be comparable for a material that is easier to work with, requires far less labor, etc etc. But they don't, and their traditional techniques work well for the area they're in. The moral to this story is, use what's local and does the job, and I feel like the only thing I got out of the video is some cool visuals of dudes building with bricks.

Of course, clay has a lot of benefits over concrete. It's lighter, insulates better, they can dig it out of the ground!

> The moral to this story is, use what's local and does the job

The content of the video is specifically directed at people of the developing world:

> this is the catastrophic reality I say in developing countries we have to go back to using natural building materials. historically we have a very rich examples of vernacular architecture that still stands we have to go back to our traditions to learn from but in the same time keeping up with the immense scientific progress so that a person from the 21st century can enjoy modern life commodities examples from South of France and Germany

Promoting locally available building materials for building houses is very different than saying one shouldn't incur any debt when building a home.

I guess titles for any documentary are going to be at least a bit intriguing, which could be the same as clickbait? But the full YouTube video title does specify it's talking about/to Africa:

"i'd rather build my house with my own earth than go into debt, Green Architecture, Africa"

I don't know quantities here - how would a bag of cement compare to two days' worth of hand-making bricks in terms of building materials?

I think a bag of cement would go a very long way for making mortar for a rock wall. Why make bricks when you can just use rocks and stick them together with a little bit of cement.

Bricks were made for uniformity so you could have it as a known quantity and spit them out of an assembly line. If you're making bricks, you've already lost this game.

The video at 6:11 briefly touches on making mortar and stone construction (along with visuals):

> binding material or mortar should be of the same constituency as the brick or stone white gypsum and sand mortar go well with sandstone mortar made of lime clay and sand is suitable for our newly developed mud bricks

https://youtu.be/f_q1pYl80pc?si=sP1GwbWT3UfFVsBW&t=371

Very favorably. Think of how big a bag of cement is. Using a timber mold like the one used in the video you can leave 100s (if not 1000s) of bricks to dry in one day. You need some materials like clay soil, straw and sand, some which might be sourced on-site. It might take a day or two in hot sun for the bricks to dry, but this can be done in large batches with enough space. They also can be fired in a kiln for extra strength, but that would forgo some CO2 benefits.

You know cement is not used to make the bricks right?

On one hand I'll refer you to the comment I was replying to:

https://news.ycombinator.com/item?id=37927320

On the other I'll point you to this common structural building material:

https://en.wikipedia.org/wiki/Concrete_block

25kg of cement is roughly 12L of 'concrete. 12L is 20cmx30x20cm (8x12x8 inches for the freedom loving folks)

From a quick Google search: 1m3 of concrete = 150l water + 250kg cement + 700kg sand + 1200kg aggregates.

Even if you used just cement and water I think you would get more than 12L from 25kg.

True, I meant pre-mixed bag of cement + sand.

>Even if you used just cement and water I think you would get more than 12L from 25kg.

The thing will crack very soon. The density of concrete is around 2.4g/cm3

a lot of that would be transport costs. So unless there are to produce the brick locally (and w/o a kiln - which would require something to burn), they are to experience similar issue with costs of the bricks.

In the video they are building the bricks on-site. I've done this before. And also built a kiln on-site with mud bricks (with a small team), though it takes a good design to get it to the high temperature required. Rammed earth is another natural building alternative where a formwork is built in-situ, infilled, and tamped down, once again with on-site materials. And from what I've seen it's absurdly strong, and can be polished such that it reflects like marble.

For extra challenge, any idea if a solar kiln could be practically used for mud bricks?

You need a temperature of about 1000°C to fire bricks, but more is better to get the moisture out. From cursory googling around it seems that a solar kiln wouldn't cut it, unless perhaps a very large solar collector was used... which upon further cursory googling yielded this:

https://helioscsp.com/concentrated-solar-power-for-high-temp...

https://cordis.europa.eu/article/id/421794-the-next-solar-re...

Interesting, thanks. :)

> The video talks about "no cost at all", except it ignores the massive amount of labour and time required to hand make bricks from mud and go from there.

Cost and labor are two different things, especially for people whose market assign very little monetary value for their labor.

> How do you house the population on this planet without making use of cheap to produce, scalable and durable materials such as steel or concrete?

Well first of all, the global population is growing at a much lower pace than it used to, so the challenge is becoming easier and easier every year.

Then (reinforced) concrete is pretty much the opposite of durable, at least with the current “cheap and scalable” technology we use today with steel rebar that corrode and eventually destroy the structure.

And finally, the current technologies aren't the only one that are low-cost or scalable, we've been working with them and refining the entire supply chain efficiency, but that doesn't mean we cannot scale other technologies. And dismissing dirt as a possible replacement because it sounds like a thing of the past makes as little sense as would dismissing concrete because that's something the Romans used.

> Cost and labor are two different things, especially for people whose market assign very little monetary value for their labor

Plus the fact that many places (including the US) have tax burdens >= 50%.

So if it would cost $50K to hire a contractor to build a minimal house (labor + materials), we'd have to first sell $100K of our own time.

On top of that we'd be be fighting an uphill battle against inflation and land scarcity.

So it really doesn't take much for this kind of thing to be worthwhile.

That's the big factor driving DIY of all kinds. And a lot of other things which look strange and inefficient.

> specially for people whose market assign very little monetary value for their labor.

Those people get approximately the same amount of lifespan as anyone else (even less, in most cases). If they use up more of their lifespan making mud bricks (by hand!) rather than learning to read, spending time with their families, or maybe even just having fun, that is a waste of their lives, regardless of what monetary value the local economy puts on their time.

> Then (reinforced) concrete is pretty much the opposite of durable, at least with the current “cheap and scalable” technology we use today with steel rebar that corrode and eventually destroy the structure.

Less durable than unbaked mud bricks? I'm... skeptical, to put it very mildly.

Please tell me you're trolling, really…

By saying that reinforced concrete is stronger than unbaked mud bricks, and that the time used in making them by hand is not available for doing other things?

That's not "trolling". Those are simply facts.

I also felt the amount of labor saved by concrete and modern building materials was not discussed enough.

The presenter does mention several times "to build your own house" and it seems to be focused on impoverished communities or individuals. This would take a lot of time and labour, but it does not necessarily beget the use of forced/unethical labour.

I thought the big problem with housing wasn't construction costs so much as the game of monopoly being played with the underlying land.

Probably depends on the country in question. Western economies are having runaway pricing issues with land, but some of the non-western economies have different problems instead.

Both are substantial and building costs is still often the majority in california.

> The video talks about "no cost at all", except it ignores the massive amount of labour and time required to hand make bricks from mud and go from there.

That amused me too but I don't see a massive amount of labor.

I do quite intense physical labor. The guy making the bricks is using only one tiny tool. You can do the same with knee pads, using tables, you can put them on plates before you put them on the ground.

I cant see how long mixing takes but say he does 1 brick in 5 seconds. Thats 12 per minute! Say we want a wall 24 bricks wide and uhh 30 tall. That takes only 60 minutes! You.. ok maybe not you... but someone used to the work can make 8 such walls in a day!

When I was 18 I got out of school with a diploma as an electrician. Most kids didn't find a job, I got one because I was just that good. I wire houses for 2.40 euro per hour. My boss charged the customer 25 euro. The houses were sold for roughly 40 000. Today the 40 000 euro house costs about 280 000. My hours are in those houses! People are buying my labor for 73 times my earnings.

I earn a lot more now of course but to buy one for 280 000 at that salary I would have to work 116 667 hours or 2917 weeks 40 hours or 56 years.

Say my salary grew from 2 to 14 euro or 6 euro on average. Then it is only 46 667 hours, 1167 weeks 40 hours, 23 years.

I would have to rent and eat too of course! Say I would have been able to live on only 5 euro and save 1 each hour. Then it takes 135 years.

in 135 years I could make 201 601 440 bricks. Enough for 10 large cathedrals.

> cheap to produce, scalable and durable materials such as steel or concrete?

Cheap as in no matter how hard you work you never gonna get one?

Don't bother with the bricks, just make cob walls a meter thick. It will last until the next ice age.

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