We discussed flattening earthbag walls in a previous blog post: Flattening Walls to Save Plaster
In that blog post (and the following Comments afterwards) I described some of the basics of this technique: tamp the sides of walls after several courses are complete; don’t wait too long or the soil will dry and be difficult to tamp; use enough clay in the mix so the earthbags are malleable; focus on eliminating awkward bulges; don’t tamp the walls completely flat – leave recesses between courses of bags so the plaster has something to grab onto.
The hyperadobe method uses mesh earthbags (see here https://naturalbuildingblog.com/hyperadobe-update-from-brazil/ and here https://naturalbuildingblog.com/mesh-tubing-for-hyperadobe/ — sorry, some blog posts have been lost). The plaster bonds perfectly to this mesh, so recesses between courses are not needed. This means you could flatten the walls on both sides to save additional plaster if you want.
2 thoughts on “Flat Hyperadobe Walls”
Maybe it’s because I’ve plastered more earthbag than hyperadobe, that I feel more comfortable with plastering earthbag. As long as you have nooks 1.5- 2 inches deep a sticky clay plaster (with included fibers) grabs on the bags well. The next smoother layer bridges between the nook infill and is strong. My only problem was where I’d over-tamped some arch bags (if you make the bags thinner to fit more in the arch, they will bulge wider than the rest of the wall…). If a couple courses of earthbags are tamped flat with no nooks, it might be good to tack some mesh onto that area. I got a crack when I spanned two full, flattened courses with the lime plaster. I patched it (lime attaches well to itself) but wonder if that will be a weak area.
I’ve plastered a little onto hyperadobe, mostly in very coarse mesh. I feel the fine mesh from Canada Bag Direct should hold plaster better than the more open tubing from MasterNet that works well for straw wattle.
But if you tamp hyperadobe much, the contained earth oozes out the openings. You will have a nubby surface for the plaster to grab. But I don’t think the plaster gets to attach much to the mesh. I suspect it’s critical that you re-wet the hyperadobe fill well. I’d like to hear how it performs over time before I say that plaster holds better to one or the other.
Adding some mesh around corners of doors and windows is always a good idea since these areas are most prone to cracking.
Our soil doesn’t ooze out of the bags. Maybe because we have less clay and we don’t over moisten the soil. And earth plaster sticks to our raschel mesh like some sort of super glue. Obviously conditions will vary and so it’s a good idea to experiment on a small structure or inconspicuous area of a wall to see what works best.