GammeldagsVanilj t1_jcaq7y8 wrote

>How do you even clean that out and make the space usable / liveable after taking radon mitigation steps?

If you've taken radon mitigation steps (such as barriers against radon infiltration from the ground, overpressure in the building or increased basement ventilation from non-radon air sources) then the remaining already deposited decay products on surfaces in the basement should be negligible. Just vacuum the place.