Many of you will remember that I’m building a timber-frame chicken coop from dying spruce trees downed on the institute grounds, shown in the video below. After felling, these trees were turned into timbers and put together into a boxy 6-×-6-ft coop. The roof was covered with scavenged cedar shingles. Right after getting the structure together, scrap pegboard was used for temporary walls. Unfortunately, a raccoon got through one of the walls and nearly killed one of our chickens, but luckily she survived thanks to the quick action of our neighbors.
Recently, I’ve been putting the permanent walls on the coop. Before studs and drywall came plaster lathe, and before that, people often used wattle and daub covered in plaster. Wattle is made up of sticks woven through uprights, creating a latticework in the open spaces. The uprights are wedged into holes drilled into the sills (horizontal members) and then flexible wood was woven from left to right, stacking up from the bottom. I added wire mesh on the outside of this lattice work to help deter any animals with digging ability: coyotes or raccoons could potentially dig through a wattle and daub wall if they were dedicated enough.
Once the wattle was in place, the daub was prepared. I drew information from Mr. Chickadee’s blog (parts I, II, and III). Daub is mostly clay and was sourced from our own property. To four parts clay, I added one part sand, a quarter part hydrated lime, one part straw, and about one part water (enough to make it into a thick paste). This was mixed on the cement slab where the coop is located and then spread by hand over the wattle. This was a messy, but fun, process that took me about a day. I was sure to push the daub hard enough to “key” into the woven parts of the wattle and when I finished the outside, the daub oozing through the latticework was easy to join up to the daub being added to the inside.
I let this layer dry for about three weeks. I couldn’t just leave it open to the elements, though, as it would dry too quickly and potentially crack, so plastic sheeting was stapled over the daub and a sheet was hung on the west side to protect it from direct sunlight. It made for an ugly coop for a while.
Then came the first layer of plaster. For this, one mixes one part lime putty with three or four parts sand and one part horse hair. Are you fresh out of horse hair? Mr. Chickadee had the good idea to cut up manila rope in 2-in segments and then shred it into fibers, so I tried this. Lime putty was a bit harder to get. Back in the day, plasterers would have large pits of lime putty covered in water, allowing it to fully saturate each molecule, but let’s start at the beginning: traditionally, limestone (Ca(OH)2) was baked in a fire until it broke down into quicklime (CaO), which is not stable in normal conditions because it reacts forcefully with water. By carefully combining quicklime and water, we get lime putty (and a lot of heat), which turns back to limestone when exposed to air, so it is stored under a layer of water to keep out air. I didn’t have access to any limestone or the year or more that people like to leave the putty to mature, so I used type-S lime and mixed one 50-lb bag with about 2 gal water — until it was the consistency of toothpaste. This can mature for years, but for me it just sat a week, but I’ve seen some people online say they’ve had success with just a few days. Each 50-lb bag covered about 30 sq ft at a depth of about 1/2 in when mixed with sand and hair.
This mixture was spread on the coop with my drywall tools: mostly a square and pointed hand trowel and larger float. This layer evened out the ups and downs of the daub and created a flatter wall. Before it dried, I used a tile-grout trowel to scratch the outside; this first layer of plaster is called a “scratch” coat because of this. The grooves will give the next layer more surface area to which it can adhere.
Next will be a layer of one part putty to two parts fine sand and a half part “hair.” Mixed and applied the same way, but thinner. This will scratched and followed by a layer of just putty, the final coat of plaster. All of this will then be whitewashed with limewash, but I’ll get into that in September.