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Remember Gautam and Kim from our crazy earthbag house in 7 days adventure?
Only eighteen months on from that workshop, and these two are already well into constructing an earthbag empire over in India. They have completed their first earthbag house, as well as planting 350 fruit, flowering, and indigenous trees to create a diverse food forest, and a vegetable garden too. But the project wasn’t without its challenges. I’m so grateful to Gautam for letting me share his experience, because it’s rammed full of great lessons.
What Gautam posted in our Facebook Group:
“I’m happy to say my first earthbag structure endured its first torrential monsoons. We witnessed over 3m of rain. I have attached a video taken after a storm (over 13 inches of rain in 24 hours!) where most of the land is flooded, and with the rubble trench foundation working like a charm keeping the interior bone dry.”
Fantastic work Gautam and Kim! The rubble trench foundation combined with gravel bag stem wall is THE way to deal with earthbag buildings in wet climates. I’ve suffered various disbelievers regarding the amount of flooding an earthbag house can withstand, but a properly built earthbag house with the right footings can literally handle a monsoon. Had Gautam followed mainstream building advice and used concrete instead of gravel, I guarantee that water would have wicked up the earthbag walls.
But of course, it hasn’t all been plain sailing.
“Lime plaster on the other hand has been tricky for me. The first time we completed the lime plaster was about two months before the monsoons and it seemed to hold up well initially…till it didn’t, with chunks falling off from sections of the wall….On the plus side, there are certain portions where the plaster is rock hard and no touch ups have been ever needed.”
Agh plaster! I always say it’s the most difficult part to master. And in a wet climate? Really tricky. After a little further investigation and some more photos, I could see Gautam’s plaster was holding up fine on the stem wall. This was because it was gravel. I realised Gautam and Kim were having the same trouble I had had with my earthbag house, but on a more intense scale.
What was happening?
Gautam and Kim’s earth’s composition was a staggering 50% clay! Normally you’d want around 20-25% clay in your earthbag mixture. In a dry climate it wouldn’t really matter. But in the wet? Clay swells when it gets wet, and shrinks when it dries. The clay inside Gautam and Kim’s earthbags was expanding like mad in the monsoon, and then shrinking back in the dry season. Lime plaster on the other hand doesn’t swell or shrink. So when the earthbags expanded, the lime plaster cracked. Had they used concrete, the result would have been exactly the same for exactly the same reason.
What can be done?
I found with my own earthbag house that it took a full dry season for the entire structure to completely dry out. Once the earthbags had dried thoroughly, I plastered again at the beginning of the next dry season, to give the plaster a good five months of baking before winter arrived.
My plaster wasn’t simple lime render though. It was clay/sand/lime/straw.
What will Gautam and Kim do?
There will be some trial and error. I think they’ll probably need a clay/lime/sand plaster which is light on clay and heavier on sand. The lime will help rid the plaster of moisture when the monsoon hits, the clay in the mix gives a bit of flexibility to the plaster, and the sand gives the strength. It will, however, depend on Gautam’s clay as to how well it works with the lime.
The Next House
Oh, once the natural building bug gets its teeth into you, it doesn’t let go! Gautam is already laying the foundations for his next earthbag house.
“We just finished the stem wall for another 6m diameter roundhouse using local laterite rock with a lime mortar. We will be starting on the earthbag walls soon and I was wondering if lime should be used to stabilize the earthbags considering the plaster issues with the other structure.”
This, in my opinion, is an excellent idea. Normally you’d use 10-20% lime in stabilised earthbags, but in Gautam’s case, I think I’d go 30% and try and get rid of as much of that clay as I could.
Gautam has plans for a living roof on the top of this house. I can’t think of a better climate for it, and I look forward to seeing the result.
Now, if there’s a man who does a job well, it’s Gautam. He researched this mission carefully, worked out the best structure for his climate and location, asked for help when necessary, and got his hands dirty in live courses. As I think is pretty clear from the outcome, he really knows his stuff. Yet he still faced challenges.
So...if you take one thing away from this build, I hope it’s this: even if you’re an expert, you’re going to be greeted by something that doesn’t go to plan. The folk who manifest mud worlds are not those who don’t have problems, they are those who face them, and work patiently and persistently to overcome them.
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