Greg Amos

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since Jul 22, 2014
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Recent posts by Greg Amos

Hi Orin, thanks for your reply and your concern.

We are no civil engineers either, but we tried to take all precautions to ensure the integrity of the tank.

In the first photo, you might be able to see rods poking out of the slab. The first layer of bags was put on those.

Then between each layer we put barbed wire, 2 lines per layer.

Finally, in order to apply concrete, we need to put chicken wire, which should further increase the tensile strength.

I like your suggestion to pile dirt around the base of the tank, easy and efficient.

By the way, the tank is 1.4 m high (outlet), 2.1 m internal diameter.

We will keep posting photos. Have a great day!
4 years ago
We are finishing our cob house in Colombia webpage, and a very important part of it is rainwater harvesting. So we decided to try to build a eartbag tank.

First we build the concrete slab. Then we build 10 layers of bags. It can hold 5000 litres. Next steps: cement plaster inside, cob plaster outside. Roofing... we don't know what kind of roof it will be. An almost flat green roof would be nice.
4 years ago
More than a year has passed since the last post, time to put some updates! We have been quite busy, with travels, design consultancies and permaculture workshops, but the work on the house is going well.

In July 2018 we more or less finished the interior walls. Then of course because the shrank, we had to refill the top part between roof and wall 2-3 times, quite an exhausting job, given that you have to work around rafters and beam. If we had to do it again, we would definitly build all the walls (interior and exterior) at the same time, to ensure better cohesion, and faster drying.

In March 2019 we covered the roof. In order to keep it as light as possible, we put sod (actually more grass than soil) directly on the HDPE membrane in some places, and gravel in others, so we could create a kind of drainage. It has rained a lot since, with hail and everything, and nothing happened: no collapse, no rain inside, so I assume it's safe to say the roof is sound

We also finished the floor. First we put the basic layers: gravel, vapor barrier and cob. It was not so great to put cob, as it shrank and cracked and was quite uneven... the best we could do was filling the largest cracks, and then we put the final (for now) layer: a lime mortar made with 1 part hydrated lime and 3 parts sand. We bought the lime in a local producer, and the quality was quite different between bags. Some produced a very nice and smoot layer that did not crack, while another batch would crack a lot and even had some kind of bubbles popping up. Now the floor is quite ok, strengthening by the day, but we will probably cover it with a water-based epoxy paint or resin for durability and easy cleaning.

We installed the electric system, which consists of a 100W solar panel, a charge controller, a 65 Ah 12 V battery and a 600W inverter. It works like a charm, we have no problems working all day on the computer, plus watching 3 hours of shows in the evening. LED lights, computer and phone charging are our only requirements for the moment, but we may have a small fridge or coolbox in the future, as well as a water pump and maybe a small washing machine.

We finished covering the outer part of the exterior walls with what we call "sticky plaster": 1 part sieved soil and 1 part cow manure. It provides a protective layer, which is also somewhat waterproof.

The interior walls were also covered with the sticky plaster, and then, because it is very work intensive to apply a clay plaster, as we previously did with the interior part of the exterior walls, we decided to paint them with limewash. We bought a better quality lime, called "type N" and put 2 coats on all walls. It looks great. The transition between the cream colored clay and the white limewash is also nice.

Finally we brought some furniture: gas stove, kitchen, table and chairs, as well as a bed.

We also advanced with the garden.

Next steps: finish the shower, which currently has a lime plaster. We will either put an epoxy on it, or a sealant they use for concrete water tanks. Then finish the water tank, and install the water system. Hopefully by the end of January we will have everyting done (even if the tank might not be full, as the dry season will start soon).

4 years ago
Hi Eugene,

thanks for your answer. The intended load is small: just LED lights and phone/laptop charging. I will follow your advise, and connect the inverter directly to the battery.

5 years ago
Hi Permies,

I am going to buy the last piece of my solar kit: an AGM battery (12V, 100Ah) (the other elements are: solar panel 100W, a 300W inverter and a 20A charge controller), and I am now a bit confused about where to wire the inverter.

1) According to Renogy, you should NEVER wire the inverter to the charge controller, but to the battery.

2) According to this video it is better to wire the inverter to the charge controller.

What do you recommend?

5 years ago
Hi RedHawk,

thanks for your appreciation  To be honest, from time to time we are in awe too. Now that we are building the inner walls, which are thinner and lower than the exterior walls, we keep thinking: "how were we able to build those huge exterior walls, only the two of us???" It must be the magic of cob. And the luxury to have the time to do it.

6 years ago
Hi Nicole, glad you like it.

Some more pictures, as we are now working inside.
6 years ago
We are now ready to move in our new cob house!

We put the HDPE membrane on the roof just before Christmas, and after some heavy rainfalls, there are no signs of leakage.

Even though we designed 4 skylights, in case it was going to be too dark inside, now that the membrane is installed, a lot of light enters through the windows, to we will leave the skylights close. It will be easy to cut the opening in the future, sould we require it.

The next steps are: building inner walls, putting grey water pipes, floors, plasters, building a ferrocement rainwater tank,...

A lot of interesting work for 2018!

6 years ago
Rene: Thanks for your honesty better safe than sorry. The structural engineer calculated a load of 130 kg/m2 for the roof, with the rafters size we are using, so you're absolutely right, we need to keep the soil layer as thin as possible. Metal roof could be an option, but I do not like them that much. I would prefer going with some 3-5 cm of soil, mixed with gravel. I calculated that a layer of 5 cm of wet soil weighs about 80 kg/m2, so I do hope we are safe with it.

Jeremy: in workdays, let's say about 60 to build the cob wall, 6 hours/day, 2 people. (and an excavator). What we spent so far. Stones and gravel for foundation: 200$, wood boards for frames and roof 400$, excavator for cob mixing and leveling 500 $, HDPE 400$ so in total around 1500 US$ so far.
6 years ago