Our house is really quite old, a couple of hundred years old, and as such it has some interesting quirks. One of which is a lack of foundations. The house sits on compacted dirt about 50cms deep before it hits the bedrock of the volcanic range we are part of.
When we bought the house, it had no bathroom. Like ninety five per cent of the houses around here, inhabited or uninhabited seems to make no difference. Houses constructed in the 1800s had no bathrooms, and so as the houses here are mostly owned by farmers who know lots of things about cows and wheat, they have no interest nor desire to engage in any DIY skills, and so each house gets decorated once a generation and very few bathrooms were ever fitted. Kitchens mostly consist of a wood burning stove of some description, or if really modern a bottled gas cooker, and a table and chair.
When we decided to include all the mod cons in our house, including a fitted bathroom, we had very little choice in its position. It went in what was once a dirt floored cellar, a 'cave'. To counteract issues of damp, we created a platform floor, constructed from treated outdoor decking, sitting on a series of beams that sit on a series of impermeable membranes, that sit on the original dirt floor, that is actually half a metre lower than it was originally to accommodate the new floating floor structure - and that took some digging out I can tell you, lots and lots and lots and lots of wheelbarrows of dirt were wheeled outside.
The upshot of this is, the floor is in effect free standing, it does butt up agains the walls but is not fixed to the walls in any way to allow for movements in the lime stone walls, and flexing caused by heat or cold. And so we have gaps. Some quite significant gaps.
And we get a few of these nocturnal visitors popping up through the gaps to hang out with us....