We've build a large bungalow using bamboo for structure and earth for the walls. The method is wattle and daub. To finish the building I need to protect the walls from rain/spray/humidity. We live in the wet tropics, bordering a rainforest, it's extremely humid with high rainfall for half the year (and pretty much dry for the rest).
I'm looking for a fast and effective finish and am considering:
ACRYLIC PAINT: I'm told this will work, but is frowned upon because it's not natural. Considering the roof is steel, the floor concrete, I'm OK with using acrylic paint if it works.
TUNG OIL: This is a natural option. Tung oil is a great natural sealant, better than linseed oil. I have a 44 gallon drum full of it, but can't find for sealing earth walls. Could I use the same mix as with linseed oil (replacing linseed with tung.
My understanding is that the problem with acrylic/similar finishes when it comes to natural walls is that they're waterproof- no water in, no water out. Makes sense in keeping the rain in and the damp out, but it also seals whatever moisture is still inside the walls, so they don't cure properly. Just like rushed/improperly cured concrete, the wall will rot over time, due to the moisture trapped inside it.
That's my limited understand on the topic, hopefully one of the (WAY) more knowledgeable natural builders around here can contribute more!
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I'd consider a lime plaster. You've got good roof overhangs, so it wouldn't be subject to much weathering. By adding a pozzolan such as brick dust or ash, you can speed the hardening and water resistance while still maintaining breathability.
Phil Stevens wrote:I'd consider a lime plaster. You've got good roof overhangs, so it wouldn't be subject to much weathering. By adding a pozzolan such as brick dust or ash, you can speed the hardening and water resistance while still maintaining breathability.
That would be traditionally used in Britain and we get our fair share of rain!
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I would go with the lime plaster, then if you should feel like you need more of a seal you could use the Tung Oil or an Olive Oil soap sealant (called Black Soap).
In all but the wettest of environments the lime plaster should hold up well without any extra sealant (once cured out).
The information I could find on Tung Oil sounds like you would need to mix it with a salt to be effective, but I didn't find enough conclusive information so far.
If I can find better info on the tung oil, I will post it here with the link so you can make an informed decision.
Thanks for the helpful replies. Lime plaster has been recommended by others. The problem is I've hurt my back a few weeks ago, so I'm quite limited, so I'm looking for the easiest effective option. Regarding sealing the wall and rot, it would not be sealed on the inside. Sealing with linseed oil is done by some, so I'm not sure if rotting is an issue. Naturally is always better, but sometimes not practically possible. I don't think I could find anyone to help with the lime plaster.
The Tung option is interesting, just difficult to get information. We're in the tropics, right next to a rainforest, it get's extremely humid here and can rain for days, although there's little wind, so the walls wouldn't get too wet, it's the humidity that concerns me more.