We have built a cat flap from the hallway to a storage room just outside our front door (then the cats have another flap out through the storage room door). After doing some reading, we realized it was important to make sure that no moist indoor air got into the insulation, so we have ensured that it is sealed towards the insulation.
However, today I saw that moisture has appeared under the wall (see picture). I wonder if it's humid air going out through the cat flap and then condensing on the floor, causing moisture? Or is there something else going on? Above, it is the same roof over both the hallway and the storage room.
Also strange that I can fit a finger in there between the concrete and the wall, several centimeters in... shouldn't there be a stud/sill there that the wall stands on? It's damp when I stick my finger in there anyway.
House built in 1988, though I think the walls are a bit thicker and there’s more insulation than typical for the 80s. The vapor barrier is located 5 cm inside the indoor gypsum.
We built this last fall and I have been in the storage room every day since then to clean the cats' litter boxes, and this is the first time I have seen anything.
