David Balt wrote:I suggest you use on site soil and amend it if you need to. You can always add lime or a very small portion of Portland cement that will really help improve the structure of your plaster. A few shovelsful of Portland will improve the plaster enormously without making it totally impermeable. My friend used soil "straight" after screening out most of the rocks, and 1/10 Portland. It dried nice and hard and has held up well.
Kimi Iszikala wrote:I'll udpate with the results, including any other mixes we make after seeing how these turn out.
Kimi Iszikala wrote:Thanks, David. I have been wondering about this. Does lime/portland make up for having less clay? Or do you need the appropriate clay content and then lime/portland helps strengthen? I am aware that lime/portland provide some water protection, but wasn't sure if it also acts like a binder (similar to clay)
Phil Stevens wrote:Tony has some really good advice generally, but I would caution against putting portland cement on either side of an earthen wall. Breathability is in both directions and if you block the exit path of moisture, it accumulates in the wall material. In wet climates, a lime plaster with sufficient roof overhang is a good way to roll. Houses in England and Europe have used lime render for hundreds of years.