Sealing

The RT reference card includes detailed sealing instructions. The joint between the foundation wall and ground-supported slab can be sealed in accordance with the examples. 

The bitumen felt is installed on top of the foundation wall and under the ground-supported slab at a 150 mm minimum width, with the sand surface and cast surface against each other. The felt is installed so that it will not break or become detached from the structures as a result of shrinkage, subsidence or other movements. 

The instructions are applicable to all types of footing details. The recommended material is category TL2 rubberized bitumen felt with a polyester support layer, such as K-MS 170/3000, weldable or glueable. The RT reference card includes figures illustrating radon control of load-bearing partitions and ground-supported walls.

Two examples of radon-tight joints between the foundation wall and ground-supported slab. The figures are from the RT reference card (RT 81-11099).

Sealing of penetrations

Penetrations can constitute a substantial route for leakage of radon-bearing air from the soil.

Penetrations made for electric cables and radiator, water and drain pipes that are led into the building from below the base floor (or their casing tubes) can be a route for radon leakage into the building. It is also important to seal any hatch structures in the slab. The RT reference card includes examples of the sealing of individual pipes and pipe groups. The sealing is conducted using elastic sealing compound after defining the area to be sealed with a suitable strip or filler.

Penetrations and slab joints must be sealed throughout the building. Neglecting the sealing in the engineering and utility services room or storage room, for example, may lead to a considerable increase in the radon concentration in the house. Penetrations are sealed from the inside and outside of the casing tube.