Putting mud on the walls

Since we have all the interior walls packed, it was time to focus on plastering. We did a little plastering a few weeks ago – just one batch. The boys both commented that they would rather play in the mud than pack the walls. So, they seemed happy to plaster.

We started with the dining area wall on Tuesday after doing some cleaning up on Monday. This was the largest of straw bale walls to be plastered, considering walls as areas between posts or on one side of a specific rooms. This wall is 9 feet tall and 14 feet wide with only one window. The thing with plastering the straw bales is that we have to work the plaster into the straw. The goal is to get it pressed into the bales an inch or two. Also, around the windows where I curved the bales, I really have to work the plaster in. I used chicken wire on the curves. So, I have to press the plaster through the wire and work it into the straw with my fingers. When the ends of the straw face outward, it’s easier to work the mud in, but when the straws lay cross ways, like most do in the curves and on the ends of bales, it takes more effort to work it in.

So, I worked the plaster in on the window curves while the boys worked on the sides and below. Once I got the curves done, I helped finish up the rest of the wall and make sure it was all pressed in to the bales as desired.

On Wednesday, we decided to plaster some of the slip straw walls. Having done a little of this previously, we knew that it goes on much easier than the straw bale walls. You don’t have to work it in the same way. Our process involved the boys smearing the plaster on the walls with their hands. I would follow with a trowel to smooth and even out the plaster. We were able to finish the wall below the stairs, the wall along the stairway, and almost all of the walls in the hallway, including in the linen closet but not the cabinet above.

We actually finished these walls in the morning and then spent time in the afternoon sifting some more clay dirt. We’re using clay that we excavated when digging the root cellar. I ran the tiller through the clay pile to loosen things up and then we screened it through 1/4” hardware cloth to remove rocks and larger clods of clay. This makes a nicer mix of plaster. We screened it into half of a 275 gallon tote – the same thing we mixed the slip straw in, only we put the metal frame around it to give it some rigidity.

On Friday, we plastered in the mudroom. We were able to get all of the walls plastered in there except for a small section above the interior door. We had two walls of straw bale and two of slip straw. There were curves around and above one window and the exterior door.

I calculated that in the three days of plastering that we mixed and applied 1,500 pounds of plaster. Once the water dries out of it, that is 1,200 pounds of plaster. This is only the first coat, too. The straw bale walls will require a second heavier coat to fill in the irregularities, maybe even a third coat. The slip straw walls will only require one more coat. At this rate, we will have several tons of thermal mass on the walls which should help moderate the interior temperature during the summer and winter.

Each batch of plaster consisted of 2 buckets of sand, 1.5 buckets of clay-rich dirt, one bucket of water, and half a bucket of chopped straw. I mixed it in the concrete mixer, using my hand to help ensure that the sand was mixed through properly. It made a nice easy to apply plaster.

We’ll be mixing up a lot more in the coming weeks.