If there is no frost in your area, then most likely you don’t have to worry.
If there are frosts and frosts, then measures must be taken so that the houses are protected from water: monitor the health of the roof; watch that the houses do not stand in a puddle; prevent the suction of capillary moisture from the soil (place the house on a permeable base, such as sand, gravel).
Treating ceramics (since it is porous) with hydrophobic liquids will give good results - this will prevent wetting and, therefore, increase frost resistance.
Look for such a liquid in your hardware stores.
An example of such a fluid - time is in hours and minutes (although the sample is not ceramic, but limestone, but the result is the same):
crummy stuff that should not be used outdoors are porous...
Still waiting on the OP to confirm which type, but your statement is not true for all ceramics, and most of what is called ceramic is not porous, like you tableware..
OK, then of very limited life outdoors... that hydroscopic liquid is expensive also, and does not last real long and does not work well on very porous surfaces.
Spray matte finish clear coat like Rustoleum enamel. Look for non yellowing. The clear will soak in and help protect the buildings and also strengthen them as it is essentially a glue. I do it with all my buildings and rolling stock as never know what can end up wet and nice to be able to wash off stuff.
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