In Portland, one component of the ADU regulation is that the siding, roof pitch, and eave style, must match that of the main house. In my case, the main house has an 'imitation-cedar-shingle' asbestos siding with a 10 3/4" reveal (the height between each course of shingles).
While the City did not want me to put asbestos siding on my house, they did still require that the reveal on the ADU match the main house. Since the main house siding was "imitation cedar shingles", we chose to use real cedar shingles on the ADU. The picture here shows the new cedar shingles with a 10 3/4" reveal to match the reveal on the main house.
Here's a video of the shingle pallets arriving from a local lumber manufacturer. The shingles are Western Red Cedar shingles from Washington state.
This next video shows the Vortex rain screen and the cedar shingle sealing process.
The Vortex which will cover our Siga wrap, and will allow rain to drain down the side of the house in case the rain gets behind the siding.
We purchased "green" shingles, meaning that they were milled recently. I bought these shingles because they were 1/3rd the cost of kiln-dried and pre-primed lumber. Because the wood is freshly cut however, there is a greater chance that when the shingles sit in direct sunlight for too long, they will start to bow and or turn grey quickly. In order to abate this process, we added a wood sealant called Penofin.
This is a video of the first shingle going into place and an explanation of the double course of shingles that we're using.
By the end of the day, we finished installing a small patch of siding on the west side of the ADU. We started shingling on the west side, the side with the least foot traffic, to perfect the process before we wrap the rest of the ADU.
It is fairly common to paint cedar shingles but I have no intention of doing that. I am thrilled with how the first section of siding looks. I also look forward to years of color and texture variance that will unfold and emerge over time due to UV exposure, rain, and age.