Radon-safe building in Finland in 2002

Slab-on-ground is the prevalent substructure in Finnish low-rise residential buildings. The gap between the foundation wall and floor slab is the main entry route of radon-bearing air from soil into living spaces. Performing the sealing work and installation of radon piping are the key measures of radon-safe building in houses with slab-on-ground. Sealing measures have been carried out in a minor part of houses due to the difficulties in the sealing practice presented in the current guidance. A new construction for an airtight joint between the foundation wall and floor slab has been studied in several test houses. Based on the results, a new guidance for a wide use in Finland is under preparation. In the new sealing practice bitumen felt will be installed underneath the floor slab in direct contact with concrete slab. The municipal authorities require increasingly radon-safe construction. (orig.)