John C Daley

From Google http://www.idph.state.il.us/envhealth/pccarpenterants.htm#:~:text=Carpenter%20ants%20are%20one%20of,a%20threat%20to%20structural%20integrity.
'Carpenter ants are one of the most common household pests in the Midwest. Besides being a nuisance indoors, these ants damage wood by hollowing it out for nesting space. While carpenter ants do not eat wood, large colonies can be destructive; however, are more of a nuisance than a threat to structural integrity.'

Vaults are usually made with thin small blocks os bricks.
one way is shown here;

and
https://www.youtube.com/watch?v=Mm15632RIAs&t=326s

Scot, I am trying to understand what you are trying to sort out?

The Russian heater would used fired clay bricks as the central core.

In areas where earth walls are exposed to the elements, such as Africa, etc annual maintenance is done to keep the structure in good condition.
They are usualy built entire of mud, maybe with some timber of leaf protection on the roof, so are 100% exposed.
Westerners ususaly have greater wealth and build roofs, wall protection with verandas etc and then that maintenance is not required.
Benjamin, where is that castle you mention?

Amber, I am in Australia and have no practical experience with frost, but I am a builder of earth buildings and have studied the situation.
The issue is the water freezing, expanding and causing damage.
You mentioned you fitted a drain at the bottom, and this may be your saviour, I have included some information, one of which deals with the addition of insulation.

the other deals with low technology solutions
https://lowtechinstitute.org/2023/10/04/frost-protected-field-stone-stub-foundation-material-saving-hybrid/
How did you get this far and decide to ask?

should add that not many here understand what you are taking about. We have one town that is 195 years old, thats old for here, and its been flooded
196 times, sometimes to 40 feet!!

Coyden thank you for that insight!
Also to Glenn and Jay.
Glenn, not many have insight the the geological details of Australia, how did you get them?

Brenda, I just dont understand what you are saying?
Did buildings and vegetation get shifted and blown down the mountain?
As for the drains, are you talking about ;
- culverts
- swales
- ditches please?

Have you thought about having a hydraulic ram moving water from the spring, close to home and draining back to the stream.
That way you have running water without walking over to get it?