We have bricked up the garage door and built a concrete staircase against the new wall. The staircase goes down to the basement and is cast on the house's slab. There is a cavity under the stairs. On the wall against the garage (inside the cavity), there will be pordrän as protection against possible moisture. There is a well in the cavity that has been connected to the house's sewage since the house was built...
My question is how we should handle the cavity. Does it need any ventilation so that the air in the cavity circulates? Drill two holes in the new wall from inside the basement so that the air circulates with the house's ventilation.
What would you do? I don't want any condensation or mold in the cavity.
The simplest solution if you do not intend to use the space for anything might be to fill it in with some light filler material. Off the top of my head, I'm thinking something like lightweight expanded clay aggregate (leca) balls. I don't know what the usual practice is, but I suppose there are many houses with these kinds of basement stairs...
