As my character is a sealmaid, she is half the size of the human shown on the scale, showing that this house is quite small. After creating my concept artwork and basic layout shape I was able to create a similar version using Google Sketchup, to make an outline.
From looking at the concept art, I added in the walls to the various rooms, changing some of the shapes slightly. I really like the unusual spaces created, yet it still sticks to the traditional Japanese housing layout.
I was then able to raise the sections of the bedrooms up higher than the entrance to show that those rooms are further inside the cave allowing air to flow inwards and stop the water coming in. As this is my first time using Google Sketchup, I wasn't sure how to create walls and a roof, but as a general floor plan I think that this shape explains my idea well.
Here is the measured version, however some measurements are the length of the sides rather than across the rooms. But this gives a general idea of how large the environment is.