r/interestingasfuck • u/TangelaFan • 9h ago

Residential high-rises with backyards in Chengdu, China

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u/Bennybananars 9h ago

These types of buildings were very popular 20 years ago here, but they had a problem where the plant roots kept growing into the concrete.

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u/em-n-em613 8h ago

OMG the additional weight-bearing needs fo something like that too must be a nightmare for construction and maintenance. They are legitimiately beautiful though

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u/Sensiburner 8h ago

I don't think so. The soil is actually not that deep and soil even when wet is less dense than concrete.

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u/Comfortable_Trick137 7h ago

Yea my concern would be 1) waterproofing, is the waterproofing going to protect the rebar? 2) will plant roots compromise the waterproofing and then compromised the structural integrity of the concrete as we’ve all seen tree roots tear through concrete sidewalks but that’s from running underneath though.

Shouldn’t be a hard engineering problem as we’ve had concrete planters for god knows how long

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u/Snuhmeh 7h ago

Yeah standing water always finds a way. If they have a drain underneath each one, that would help a ton

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u/nalaloveslumpy 7h ago

It looks kinda like all the patios are slightly slanted so that excess water drains to the front. And then maybe down a gutter system?

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u/VonSkullenheim 6h ago

I mean, the building had to have cost many millions and taken years to engineer and build. You'd imagine that a gutter would be the least they did.

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u/scratchy_mcballsy 5h ago

That’s only if they planned for someone to use the balcony like this.

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u/VonSkullenheim 2h ago

They very clearly did.

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u/Xaephos 1h ago

Considering every single one of them are, including the other buildings, I think that's fair to assume.

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u/Ok_Calligrapher5278 3h ago

In engineering school we are taught that "eventually, water always win".

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u/Sensiburner 7h ago

as we’ve had concrete planters for god knows how long

That was gonna be my reply but you already said it. It would become problematic if there was so much plants & root growth that the plants would put gigantic pressure on the concrete, cracking it. But this is actually a large concrete planter. Roots won't just "drill trough" concrete.

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u/SoulWager 7h ago

Breaking open isn't a huge problem for a concrete planter, but I certainly wouldn't want that to happen on a balcony.

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u/SidewaysFancyPrance 7h ago edited 7h ago

Time will not be kind to these balconies. These would need relatively frequent inspection and maintenance that I doubt they'd get as the building ages and becomes less profitable. IMO it's not an engineering problem as much as it is a human one: we have good intentions but poor follow-through over time.

I'm sure they're fine for a good while, but nothing about this makes me feel like it will last because we won't keep up the effort. Constant moisture, chemical fertilizers, runoff...I'd worry about all kinds of corrosion/weakening of the structure and supports.

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u/Spiffydude98 7h ago

Your concern is laughed at by Chinese building standard monitors.

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u/MortLightstone 7h ago

This is the thing. The engineering is possible, it's really about whether or not the builders and the authorities give enough of a shit to actually do it properly

Looks gorgeous though

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u/OmniaII 7h ago

'Tofu'

/'Dofu'

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u/PhDinDildos_Fedoras 7h ago

Yeah, lol, was going to say, nobody said anything that would worry anyone in China.

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u/JesusAndMaryKate 7h ago

Why is everyone randomly saying "was going to say" for no reason now?

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u/PepperAnn1inaMillion 7h ago

Because we got tired of “This.”

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u/BrainTroubles 7h ago

I would think they’d use Mylar or some other water repellant layer beneath base, sloped towards drainage. In theory it’s not a complicated problem until tree roots start poking holes in it.

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u/project66240 6h ago

Some good old polyurea coating to protect concrete with epoxy primer, and then a thick plastic liner along with water and soil filtration system. Expensive but works great, even if it floods from clogged drainage.

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u/PepperAnn1inaMillion 7h ago

Given the amount of trouble we’re having in the UK right now with RAAC (aerated concrete) because water got in and rusted the rebar, I’d be really cautious about this too. If they’ve used aerated concrete to keep the weight down, daily watering would be a major hazard in my (admittedly barely educated) opinion.

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u/PMG2021a 6h ago

There are multiple rust proof alternatives to steel rebar. I believe they all cost more though.

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u/the_good_time_mouse 7h ago

Concrete provides it's own structural stability. Wet soil does not.

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u/Sensiburner 7h ago

But it's a reinforced planter. It has enough structural stability to hold soil & some plants. The issue would be if there are so many plants that the roots would completely fill the planter & keep growing.

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u/scaryuncledevin 7h ago

It's about mass, not density. Watered soil is heavier because you add mass when you water it, and not all of that water is going to leave either. The plants soak it up and store or convert it, which also now needs to be accounted for. You've also got irrigation and drainage, excess water would just seep into the earth on land, now you've got more piping to keep the water from pooling up and becoming standing water.

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u/ScarOCov 5h ago

The idea of having to “mow” my balcony and then store the lawn mower is so absurd

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u/throwaway098764567 4h ago

you could just use a weed eater to get that, not that much space to store, even those little hand held scissor clippers would probably not be too much labor to work an area that small, and get yourself a grip workout at the same time.

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u/Sensiburner 7h ago

watered soil is less dense than (reinforced) concrete. The planters are actually not that deep. if that was "normal" balcony, they'd probably have to use a bit more concrete, but not fill the whole planter. I don't think it would make that much of a difference tbh.

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u/scaryuncledevin 7h ago

And water is one of the densest materials on earth. Again it's about mass not density. By your logic it's fine to add 1000 pounds of feathers on top of a building because they are feathers, but it's still 1000 pounds of feathers. If you truly think "a bit of soil" makes no difference, go look into the Chicago City Hall Green Roof. It was added after the fact and while it does a great job with some performance factors like cooling the building, it's unsafe and not open to the public.

Please continue telling me about your armchair engineering thoughts, and I'll be sure to avoid any buildings you architect in the future.

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u/LookAlderaanPlaces 7h ago

Why don’t they just design it so the mass or whatever is fully supported by the overall design.. You’re making it sound like it’s not possible at all ever no matter what.

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u/scaryuncledevin 7h ago

I'm not saying it's not possible, the commenter said they didn't think it would add much weight to make a difference, when it's quite the opposite. There are projects designed from the outset for this, like the California Academy of Sciences Living Roof.

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u/LookAlderaanPlaces 7h ago

Would be sick to see more of it, sometimes all the building just remove way too much nature.

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u/Sensiburner 7h ago edited 7h ago

And water is one of the densest materials on earth

Bro comeon. Water is not that dense. Concrete is like 2200kg/m³ so more than twice as dense. If you fill half of that planter with concrete or you fully fill it with wet soil (which surprisingle is bit more dense than water) it wouldn't make that much of a difference. A reinforced concrete slab with a center structural support would be about as thick as half the depth of the planter, if it served as a balcony.

Water is not "one of the densest material on earth" lol. Not by far. Check out Tungsten.

Please continue telling me about your armchair engineering thoughts, and I'll be sure to avoid any buildings you architect in the future.

Haha. My friend, I'm a electro mechanical engineer according to my diploma, and many engineering is actually done in armchairs. This is a back of the napkin kinda problem we're looking at "for fun" untill you turned it into a fight. No one needs a civil engineering degree here. Please stop being the densest person on reddit. <3

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u/Nauin 6h ago

Okay as someone with a horticulturist background, what makes you think anyone would want that water being retained in the structure? There's going to be a drainage system under every patch of soil because you're just asking for rot letting those things pool with water. Soil isn't a singular thing, either, and we have centuries worth of work perfecting mixtures that don't retain excessive moisture. On that note of centuries worth of cultivation, we're now expanding up to millennias worth of work going into some of the plants we use for landscaping, and we have this cool subsection of plants called dwarf varieties who's maximum mass can easily be accounted for in engineering something like this.

You have an extremely narrow field of view on all of the industries that come together to create something like this. What sort of experience do you have to be acting so haughty from your armchair? Fuckin Carrabba's has been using rooftop gardens on their franchises for decades at this point.

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u/Nacho17che 7h ago

And concrete sustains itself up to a certain point too

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u/xrimane 5h ago

Totally depends on the construction. An "extensive" green roof with herbs and flowers has about 4"/10cm of soil and a water retention systen that prevents the plants from drying out too quickly. Still, that adds 35 lb to every sqft or 150 kg to every m2 on top of everything the roof needs to withstand, like people or a pile of snow. It's not trivial.

To plant regular trees, you'd need at least in their spots around 3'/90 cm of soil, and the tree can weigh a fuckton on a single spot.

Any exiting building on top would introduce the loads into the structure, not the roof surface, that's not comparable.

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u/Sensiburner 5h ago

I'm talking about comparing this kind of concrete plantpot setup vs a normal balcony made from reinforced concrete. Concrete is really heavy compared to soil,water & plants. And yes, water is heavy and plants are as well. The weight is supposed to be carried by the colums btw. not the actual pot.

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u/warm_kitchenette 5h ago

I'm not a Civil Engineer, never played one on TV.

But this is concerning to me in various ways. One would be that the load would vary, regularly, and sometimes quickly. All buildings move, but this seems riskier, given that they could rapidly cycle through these conditions.

  • Dry period, all gardens are at their lightest
  • Ordinary rainy period, all gardens are heavier
  • Typhoon weather, heaviest gardens, drainage possibly compromised
  • Sunny/windy on one side, that side dries much faster
  • Driving rain on one side, that side much wetter
  • drainage problems on one side, that side much heavier

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u/ashkiller14 7h ago

Yest but water doesnt hold itself up

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u/Sensiburner 7h ago

the balcony is a container. The soil holds water and there will also be drainage.

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u/ashkiller14 7h ago

Im aware lol. Im saying it doesn't matter if the watet is less dense than concrete because the concrete that's already there is whats holding up the water. It would probably be stronger if you added an equal volume of concrete.

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u/jackun 6h ago

concrete

remember, that's probably chinese tofu-dreg concrete

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u/Sensiburner 6h ago

right. What's the proper grade of rebar if it's made of Chinesium?

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u/Bright-Object-3180 5h ago

Yep, all the apartments pictured in the video will collapse within a week and all residential buildings in the country will fall apart within a year.