House L is a hempcrete with clay in-situ cast project. The tree house was built by the owner who took on the challenge of being the builder. Hempcrete and clay were used to construct all the walls in order to maximise the thermal benefits of the indoor climate. For breathability purposes, the walls were plastered with airPLAST and hempPLAST. The substructure consisted of gum pole timber. Through this project, we learned that shuttering could still cause bulging walls, but small timber pieces could be used to keep the walls plumb and straight, as long as they were tied into the shuttering.