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[BubbleCat]

Cheap and easy for concrete: waterproofing paint. but on hypertufa it might be a problem because of the wanted high porosity, you had to apply lots of waterproofing pain.

Those porous materials like clay pots, hypertufa, concrete ... all leak water, but slowly if the water contained is more wet soil and not a swamp. So if there is air surrounding it you will most likely not even realise its leaking since it evaporates at least as fast as it leaks.

The problem will be found at the base, where you want your water the least (roof) theres no air and so nowhere for the leaking water to evaporate, it will then creep into your roof.

But note: you might face a similar problem when using perfectly sealed containers, when it rains the water will creep into that tiny gap between container and roof (both surfaces are by far not flat) and there it will evaporate much slower and may cause issues.

So: If I was you and was worried about the roof I would make sure the contact patch between whatever you come up with or decide to go with in the end is minimised, this means: put singly bricks underneath allowing much air in between your raised bed and roof, or even wooden stands or whatever. Dont just place a big sheet of something directly on your roof, the first rain will go under it and mess with your roof and the sheet itself.

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[Radium]

Yeah, due to full sun and hot weather we have here, water will evaporate before being able to leak into the roof materials.
I will elevate the entire container using wooden stands or bricks, about 10-20cm, to allow a large amount of air circulation under the container.
And won't place any sheets as you mentioned. Good note.
So we have no problem with leakage anymore.

Now back to another problem:
Which of these materials can tolerate being in contact with water for years, without crumbling into a heap of wreck?

• Hypertufa
• Papercrete (paper+plaster of paris)
• Papercrete (paper+clay)
• Papercrete (paper+cement)
• Concrete

1 Like happyconcacti likes this.

[BubbleCat]

If you dont waterproof it (paint / plastic lining ...): None, if you do: All

None of those listed is absolutely waterproof of its own. With concrete theexact formulation will play a big role.

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[Radium]

If you dont waterproof it (paint / plastic lining ...): None, if you do: All

None of those listed is absolutely waterproof of its own. With concrete theexact formulation will play a big role.

Then both of these non-waterproof hypertufa pots are gonna destruct after a few years?






I don't have any problem if a material is porous and water leaks through it, I just need it to keep its shape and density for a long time. Do you know any such material?

[BubbleCat]

As long theres no freezing absolutely not going to destruct, thanks to porousity its even pretty frost proof. If you go with something that leaks just remember keeping it off the ground.
Just remember a whole hypertufa raised bed will be heavy.

Also keep in mind you might want to go with several single hypertufa units then, since ridgidity will be greatly reduced with size until it needs structural reinforcements or simply fails, especially when only supported on the corners to allow air under. And you will be basically making 3 rooftop gardens as you will most probably need a positive and a negative mold. Good thing is: you can include the standa on all corners into your design.

[chamomeleon]

Sounds like we've covered all the bases then

[BubbleCat]

So... youre stuck with hypertufa for your rooftop gardening, you want to allow air under it for good ventilation and no moisture buildup, IMO you want individual units you can move around and that are sturdy and ridgig, you will need a two-part mold, and so on.

Good I have put my thoughts on paper and as always have sucesfully messed up the perspective but it should still be clear.

In step one you take a square baseplate (lets assume you use plywood, preferably sealed plywood) of desired dimensions a x a x t (t being uniform thickness of all plywood used). Next you want to put a wooden beam section a x b x b centered across the basplate and secure it into place with two plywood / spax screws from the opposing side of the baseplate. Then you want to complete a cross with two more wooden beam sections (a - b)/2 in the same manner.

Then in step two you want to attach 2 rectangular sheets a x h x t (h being desired height) opposing to each other and lining up with the edges of the baseplate using more screws which will hapilly go into the wooden beam cross and the baseplate. Then you want to complete the box with two rectangular sheets (a + 2t) x h x t opposing each other and attached in the same manner and additional screws at the top where theese sheets overlap the previous to due to the added 2 t in width. Then you have a nice box with a cross at the bottom.

Next you want to choose a desired thickness for all walls and the bottom of your gardening container, once done you want to subtract twice that thickness (only once in case of the bottom) from the inside dimensions of your cross and construct a plain rectangular (maybe slightly tapered) box with exactly the resulting outside dimensions or pick any existing container or shape or even base your design around one. If you want a drain hole its not time to place a candle section on top of the center of the cross. Then you want to fill in the box (lets call it negative mold) to the calculated height for the bottom of your container over the cross (so basically to the top of the optional candle section). Next you want to place your positive mold (rectangular box) centered in the negative mold so it sits firm and level on the layer of Hypertufa you poured in. Then you want to simply fill all of the remaining gap in between positive and negative mold to the top and let the whole thing cure. After cure time that has to be determined experimentally (but better safe than sorry) you want to remove all screws and pop the negative mold apart and remove your wooden beam sections from the bottom of your resulting hypertufa container and try to wiggle the positive mold out (here it might come in to play that it can be tapered or maybe collapsible or sacrificial).

If everything works out you will have a hypertufa planting container with a drain hole at the bottom and a space underneath that allows for good ventilation of the rooftop amd maybe a small container to catch and evaporate draining water. Being square and of uniform height infinite equal containers could make a big rooftop jardin that can be rearranged as you like.

Be sure you stay away since cement can be quite ... caustic ? No inhaling not in your eyes and maybe not on your skin at all.

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[Chicsa]

Very nice exploded axonometric

1 Like BubbleCat likes this.

[BubbleCat]

Shhhuuuuushhh ! I always confuse wether I am busy with sth Iso- di-  trimetric or oblique and orthographic or perspectivic thus things get crooked

But as soon the idea gets physical shape everything is always right since I know what was meant

[Radium]

Nice explanation Bubble!
I will do it as you said, lots of identical square pots, that can be placed around the rooftop in any fashion imaginable.

I'm currently doing a lot of composting, because soon I'm gonna need A LOT of good soil for the many new pots.
Good soil is expensive (in that amount), thus why not just make my own compost and mix it with free earth soil to make my own good soil?

I had one bin before, today I increased that into 5 bins.
5 bins full of kitchen waste and maize pods.
My preferred method is keeping the bin lid open for flies to get inside.
Then after a few days, I put on a fine screen mesh on the head of bin, to prevent newly born flies to escape out of the system.
So they keep reproducing inside the bin, and they do this until there's no food for them inside the bin, then they all die and become fast decomposing food for microbs.
Using this method I've made a lot of compost in the past.
Since flies cannot just eat your materials and then run away, you end up with a lot more compost than if you left the bin open.
And the compost is ready in a month or two, depending on the season.
I just love compost and composting, it looks like magic to me.

THE LAST QUESTION:
Since cement is only sold in bulk (+200kg) here, obviously I can't get my hands on cement, unless I go crazy and buy 200kg, and the bulk remaining of it will be wasted due to air moisture after sometime.
My favorite material is plaster of paris, it's cheap and can be bought in any amount I like.
Mixed with paper, it makes a wonderful material with many benefits.
It's very light, and the casting process also will be a lot shorter in time, since 5 minutes after pouring it inside the mold, it will harden up, and you can remove the pot and use the mold for making another pot again.
That way I can make 20-30 pots in some hours, and let them dry in the sun for 1 day, and they're ready to go.
My only concern is the longevity if left to be in contact with water/moisture.

Does pots made of paper and plaster of paris have the same properties of hypertufa regarding porousness and longevity?

[chamomeleon]

Plaster of paris is what they use to make limb casts.  When a cast gets too wet, it turns to mush and sloughs off.  Honestly, if you want structural integrity with that material you kind of have to protect them from water.  Otherwise, all your hard work is ruined 

If they're water resistant/ proof, and aren't roughed up too much, they'll probably last you a couple of years before you need to replace them.

[Radium]

Won't the paper fibers help it to keep its shape?
I should experiment it.
Even if that withstand one full year, I'm happy with that, and will build another batch next year.

[BubbleCat]

All that structural integrity from fibers only works as long your plaster is dry hard and makes good bonds, as soon as plaster and fibers are wet theyre not good for anything anymore.

Plaster can get wet and dry of again to certain degree so id say if you dont have a lot of rainfall waterproof your containers and the drainholes from inside with waterproofing paint, if rainfall is an issue too cometely paint them.

You might want to come up with dimensions for your pots, calculate their volume, decide on the ratios of perlite cement sane organic matter ... you want to use and make an educated guess how much of the 200 kg youd be using, then investigate if there is any project of yours or friends that might use the remaining cement or investigate if you can store it in airtight containers with lids for future use.

Maybe go to a random building site and ask if a crate of beer or similar donation to the workers gets you a sack if cement (which already is 1/4 of the 200 kg).

Having acess to plaster you might want to investigate your acess to clay - what does your soil consist of ? Can you fire clay ? Plaster makes a fine slipcastin mold that will produce identical pots of desired shape.

1 Like Radium likes this.

[Radium]

Yes clay is cheap as dirt here, because it's everywhere.
The native soil has a lot of clay content.
What is required to bake the clay pots?
Can I bake them inside a kitchen oven?

1 Like Chicsa likes this.

[Chicsa]

You can do a Chickasaw method where you fire it in a pot of some sort (pictured below is a trash can) outside, very easy to do

https://www.chickasaw.tv/culture-keepers/video/pottery-drawn-to-chickasaw-history/list/crafts

This video has some information on it too. The beginning process is called Coil Building Method, done usually with a prayer.

BTW BC Isometric = 30/60 angle Axo=45 degree angle Plan Oblique is any extruded drawing of a plan at any rotation... iirc. But honestly theyre all interchangeable and used inconsistently so lol!