Consulting a number of dictionaries they each say similarly a building for human habitation consists of a ground floor and one or more upper storeys, living quarters for one or a few families, a shelter or refuge (such as a nest or den) or a natural covering (such as shell) that encloses and protects an animal.
For a tree house (the first one noted in 1868) as described to be a small building, structure, or shelter built among the branches of a tree such as a playhouse
From this, one can only take a house to be a place that will protect the occupier from the weather meaning it has weather protection from the sides and the sky.
The photo in the ODT does not show any weather protection so everyone is incorrectly using the word house. At best, it may be described as a structure in a tree. Does that need compliance?
It would only a temporary structure and probably removed at a later but unknown date.
On the internet all photos of tree houses show protective floor, walls, and roof.
- Rowan Leck
