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How to waterproof my green roof? For planting on top  RSS feed

 
Xisca Nicolas
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Posts: 1320
Location: La Palma (Canary island) Zone 11
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I have to remove rain infiltrations in a terrace.
I have tested it during 2 winters: a plastic sheet is absolutely efficient to do the job.

I would like to plant pineapples afterwards, because they need little water, and moreover, little soil!

the idea is to waterproof and then to cover with soil.
Cement + earth?
Special rubber/plastic sheet + drainage with stones + earth?
When about the excess water? And that it does not remove soil.

They say those special plastics last for at least 50 years.
ok for me, glad if I do the same by now!
But not so ok for the future.

If I put cement, humidity will make it rot sooner or later, but I do not know when.
If I use a sort of special paint, I do not want to remove earth and plants to check out and re-do the painting....
Lime?
It is supposed to get harder when wet, and go back to the state of stone.
But which type of lime?

Should I forget about planting and do a stone roof?
I have so many more things to do that cost is also an important factor...
 
Xisca Nicolas
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Posts: 1320
Location: La Palma (Canary island) Zone 11
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I have to precise:
I also have a little cement roof (= with air under it!) on the side of the terrace, that I want to cover and plant. This one is 20m2

What I called a terrace up there, is a piece of garden. It is earth.
As I am on a slope, imagine the Andes... A wall down side, and a wall upside...

It is about 15m long, and 5m large.

As I have no room to remove stones and earth that are already there (I cannot stock), I want to separate the terrace in 3, with walls. If we waterproof the highest part, it will anable to use much of the extra material first. At the same time, the "stair shape" will help me for te access!

So, What I imagine at the moment are sorts of shallow pools surrounded with walls.

If this is difficult to waterproof and AT THE SAME TIME plant on top, then I will change the plans if I have to.
My absolute priority is to waterproof the soil, this place being my roof.
Thanks
 
Christopher Borton
Posts: 6
Location: Whitehall, MT
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Hi Xisca, I'm having a hard time visualizing your project. Are you thinking of earth roofing a concrete slab/ terrace so that you can plant on it? if you had a sketch or photo of your project you could attach, that would help a lot. Thanks, Chris
 
Bill Bradbury
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Location: Richmond, Utah
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Xisca Nicolas wrote:
If I put cement, humidity will make it rot sooner or later, but I do not know when.
If I use a sort of special paint, I do not want to remove earth and plants to check out and re-do the painting....
Lime?
It is supposed to get harder when wet, and go back to the state of stone.
But which type of lime?

Should I forget about planting and do a stone roof?
I have so many more things to do that cost is also an important factor...

Lime and clay makes a great barrier to infiltration and is being studied to replace plastic liners in landfills.
Abstract:
A series of permeameters (columns) was used to evaluate the effects of the percolation of water and 1,000 μg/mL of zinc chloride solution through a mixture of montmorillonite clay, sand, and lime. The column test results show that the addition of lime changes the chemical and physical properties of the clay. The hydraulic conductivities for the mixture of clay with different percentages of lime at first increases with increasing lime and then decreases with increasing lime. The breakthrough curves indicate that the Zn(II) capture is increased and Zn(II) breakthrough is delayed with increasing lime addition. Lime also enhances the clay/lime mixture`s ability to resist puncture by sharp objects. Based on the effects of lime on Zn(II) captured by the clay, an explanation for the interacting effects of lime and Zn(II) capture on changing hydraulic conductivity is suggested. The results of this research demonstrate the potential of using lime-treated clay liners for landfills. Such liners would have lower hydraulic conductivity, better resistance to puncture, and enhanced ability to capture heavy metals.

You can also shingle stones that are set directly into the lime/clay to ensure heavy flows are diverted as well.

Then there is this thread wofati-earth-berm/WOFATI-cob-plastic
 
Xisca Nicolas
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Posts: 1320
Location: La Palma (Canary island) Zone 11
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Christopher Borton wrote:Hi Xisca, I'm having a hard time visualizing your project. Are you thinking of earth roofing a concrete slab/ terrace so that you can plant on it? if you had a sketch or photo of your project you could attach, that would help a lot. Thanks, Chris


The reverse, that is why I added a 2nd post
"What I called a terrace up there, is a piece of garden. It is earth.
As I am on a slope, imagine the Andes... A wall down side, and a wall upside... "

My question is mainly about "what is the most efficient and durable for waterproofing soil?"
I am not fond of plastic,
cement will "rot" with time if wetting and drying according to the periods of the year and plant watering.

The lime I can buy is hydraulic lime. Also the common white lime used to paint walls for example (it is softer than hydraulic lime).
Bill, thanks for your answer. I have learned that hydraulic lime is not good to mix with clay!
I do have access to clay, but a very difficult land (steep, difficult access)
They say that aerial lime is fine with clay. (dunno the reason)

Thanks for the link and idea I will edit... HAVE lookED at them.
So, I have hydrated lime! That is not supposed to be mixed with clay.
I look for adequate pics to show the place...
 
Alder Burns
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Posts: 1389
Location: northern California
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You might think along the lines of the carpet-sandwich idea for pond liners. I've roofed a couple of cabins with a similar technique. Basically you protect a couple of thicknesses of heavy plastic with carpet (or something else durable and puncture resistant....I've uses silt-fence fabric in a pinch) on both sides. In a pond, algae and mud build up on the upper carpet.....and soil and rocks can be put on top of it where it is above water, mostly to protect it from slowly degrading in sunlight. For the cabin roof, I laid the plastic in overlapping courses on a deck of cardboard placed on the frame, and then covered this with overlapping courses of carpets, which were then stuccoed with a soupy mixture of cement, which hardened in among the carpet fibers and formed a rigid surface. Moss eventually grew on it, and I imagine some soil could have been added and a living roof done that way. The roof, of course, had some slope to it......
 
Terry Ruth
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Bill, I'm not sure that the lime added to clay is to eliminate plastic but rather keep it from rupture by giving it a stronger backing and wetted strength, as we seen on the Breathable Wall thread it did not affect permeability either. Flyash helps freezing and thawing. The Civil Engineers I talked to here use a very well engineered and tested composite of clay and lime, plastic. The clay content can vary in just a few feet apart, alot in a land fill or even building lot, so they have professionals that understand this completely, since the EPA is breathing down their necks.

It's difficult to get around plastic on a roof, especially low pitched or flat live ones that collect water.

Xisca: One way is to create a gap (3/8 or larger) between the roof cladding (soil, slate, shake) using MGO boards (2). The lower one sits above insulation, the upper below your roof cladding as sheathing. You insulate below the lower and this could be sealed(for very cold climates) or open vaulted or attic. In cold climates, a raised heel truss or "energy heel" stuffed with insulation (cotton dries fast, or inert mineral wool drains and dries fast to the vent/outwards). T&G ceiling. No tapes or caulks on any joints provides a fully breathable assemble, the parge coat provides an air seal too. MGO absorbs and dries much faster than wood sheathing, inert, non magnetic or thermally conductive, needs no barrier.

A parge coat of MGO/lime/clay (kaolin preferred) acts as a capillary break applied to the vent/rain planes, or lime burnished by wood or steel trowel (NHL 3.5 ) on the lower upper surface, NHL type 5 common to your soil burnished since it's denser and rated for water. Two layers of a highly absorbent /desorbent MGO board with all natural surface treatments parge coats for vapor, a gap for water drainage and ventilation, and inner layer of clay or lime plaster or wood provides triple layer water and vapor management/protection. Run some water proof small sample ground test first with the parge coats to get the mix right, especially the one with the NHL 5, but even if it fails it drains to a ventilation/drainage gap that air vents between the soffit or open overhang and ridge vent, or attic vents, or turbine cans. If you can use well drained soils/plants or per-lite/vermiculite that would help capillary wicking to the insulation or roof leaks due to gravity and pressures, and reduce mold growth. May not need rain and ice on the edges but may not hurt the lower 6 inches if it freezes there, if you can find a non-toxic high perm rated one.

A substitute for MGO board would be low density fiber-cement board if you can find a company like Durisol or Faswall over here. They use portland cement and clay or ceramic mineralize recycled soft woods that neutralize or petrify the wood so it bonds better to cement, like wood chips and clay, but in a sheathing board. OPC provides an alkaline or high PH (above 7) surface to prevent mold.

"I have learned that hydraulic lime is not good to mix with clay!
I do have access to clay, but a very difficult land (steep, difficult access)
They say that aerial lime is fine with clay. (dunno the reason)"

This is not true, the difference between the two is one has more air than the other, that is all. NHL's contain clay from manufacturing limestone which naturally contains some clay. We have been using AG lime (high calcium, little MGO) with soils for a long time and still do, Fly ash too which is considered a pozzolan or geopolymer, has calcium and other ingredients depending on grade. It also has heavy metals (very small traces) some do not like. Do not worry about the color, each manufacture has a different burn process....look at the content and usage guides the manufacture offers on the label/MSDS/SPEC sheets or call them. We use primarily type S (your 3.5) in the US, or N (your NHL 2), NHL 5 gets close to our portland cement we mix with S or N, or SA / NA, A=Air Entrained or additive, if we want more air insulation, same is done with your NHLs.

Hope that helps.
 
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