Izita Caddis?

If it looks like a caddis and behaves like a caddis, then it most likely is a caddis.

But I am not entirely convinced.

This blip today is less of an artistic blip and more of a scientific curiosity.
I have been doing some repairs and DIY at my mother's house which dates from the 1930s and is built in a mock-Tudor style. The white walls were last re-coated with a rough textured masonry paint about 5 years ago. The wall faces SE and is shaded by a tree. It has attracted a light accumulation of algae (Pleurococcus?) on part of the protruding texture.

Three days ago I spotted two of these minute creatures about 6ft above ground level. Size about 5mm long - the inset shows a dressmaker's pin for comparison.
They become active as it gets darker and appear to be grazing on the algae. The furthest one moved in a single night was just under 3ft.

They live in a case made of minute grains of mainly dark sand and detritus giving the appearance of a true caddis larval case. What I can make out of the creature itself looks like a caddis larva.

BUT . . .
They are living on a dry wall.
Most caddis larvae live in water though a few live in damp moss in woodland. I know of none that live in such arid conditions as a painted wall.

So, my question is:" Is it a Caddis?"

(Yes, I know this is not the best site to ask such questions on, but you can all have first a bash at it before I repost it elsewhere.)