Second Coat Plaster- Filling and Detailing

Second coat of natural clay plaster

The second layer of plaster for this strawbale house consisted of layers of fills and details to level out the lumpiness of the bales, which was a result of not doing any trimming to the bales once they were installed. This is because of the orientation of the bales as they were stacked into the framing of the walls, which meant they were string side out and unable to be cut. (See this post for details!)

Generally the same process for second coat plastering applies that I described during the building of our first straw bale house (see this post…). The main difference here is that I did a round of filling in the sections that were significantly dippy, (which was generally around the perimeter of the bales), letting that dry, and then covering the walls fully with the attempt to keep the plaster thinner in the lumpy spots and thicker in the indented areas. If the plaster is too thick in the dips, it will crack too much as it dries. The window edges also had burlap which needed to be embedded into the second coat to keep the plaster from pulling away from the wood, and there was some extra shaping needed in the curves of the window openings as we couldn’t trim the bales ahead of time into the curves we wanted.

We created wire forms above the hallway openings to create a curved archway, which then needed two coats of plaster. We also plastered over the interior bedroom walls that are constructed with 2×4 framing and rock wool insulation covered in metal lath. The bottom of the upper story exterior walls needed flashing installed, which we plastered into the wall also using metal lath.

The final purpose of the second coat of plaster other than protection of the bales, is to create a surface that supports the final clay plaster, especially at all the various edges. Once the windows and doors were installed, more plastering details were attended to- wherever the clay plaster meets window sills, frames, counters, kickboards, ceiling boards, etc., there needs to be a tight edge to within 1/4 inch for the last layer to fill. This can be finicky and involve a lot of unique areas that need extra attention and thought, and will be different in each build.

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