We made the adobe into lumps approx 7cm wide and built them around and upwards in a spiral.
If too dry, they don’t bond well. If too wet, they become saggy under their own weight….Make sure your sand dome is dry first! You can be quite brutal with throwing the adobe blocks into position. A moistened surface helps them stick and bond more thoroughly. It is worth patting them to make better connection and seals. I later found the inside lining was not particularly smooth and looked like a pile of unpointed bricks.
We built it up and let it rest for 24 hours including a sunny day.
We cut a doorway using a kitchen knife and were pleasantly surprised to find how strong it was, ready for the sand to be scooped out into the wheelbarrow.
I am told the doorway should be 63% of the interior height for optimum airflow. I am sure a little error either way should be ok!
Next: a small fire to help dry out the adobe. As moisture leaves it’s strength increases. However you don’t want it to be too dry or layer two will not stick well.
I have also cemented two house bricks at the front as base for the arch. (Use fire-cement unlike me!!)