“How to choose your exterior plaster?
1) make it breathable — this refers to the ability of a material to allow humidity back-and-forth through the surface (it does not mean there is literally air flow through the material). A breathable finish will not allow humidity to get trapped inside a wall and so will allow a well-detailed wall system to stay dry over time. Clay plaster is the most breathable finish, with a perm rating of 18 (high is more permeable); lime plaster is a close second with a perm rating of 14.
2) decide your desired maintenance — clay plasters are softer than lime plasters, so if you have significant rain AND the roof overhang does not substantially protect the plaster from rain, then a clay surface will require occasional re-plastering or patching. Lime plaster is quite strong and so is resistant to erosion from rain (and so requires less maintenance).
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3 thoughts on “Build Naturally with Sigi Koko”
Hey Owen, hope you are well. Just saw a link to this blog post and wanted to let you know that this is not one of my projects. I’ve done tons of natural buildings…this just isn’t one of them. Thought you’d want to know.
Hess pumice in Idaho now offers a lime based plaster that is a mixture of pozzolan (pumice fines) and lime that will last for generations and is breathable
This pozzolan lime plaster sounded great until I got to the part where their website says they only sell to certified applicators. That doesn’t help most of our readers.