Constructional measures against radon

Simple and cost-efficient measures can be used to protect a building against high levels of radon exposure. Preventative protection measures planned in new buildings are to be preferred over subsequent remedial actions in existing buildings.  

However, depending on the situation, older buildings can also be protected against radon without much expense. Each measure relates to one of the three basic principles of radon protection:

  • Radon is prevented from entering the building
  • Radon is actively removed before it enters
  • Radon is conveyed out of the building

The most commonly used methods for reducing radon exposure are described below.

Preventative measures in new buildings:

No two buildings are identical. Consequently, when planning a new building it is impossible to predict the radon gas concentration. However, preventive measures in new buildings are much less costly than subsequent remedial action.

Concreting the basement: foundation slab


In order to prevent radon from entering the building, the building envelope that is in contact with the soil must be sealed. This requires a continuous foundation slab and walls that are in contact with the soil should be constructed with concrete of the exposure class XC2.

Moreover, air-tight inlet and outlet ducts for cables, water, waste water etc. are very important e.g. with a pipe duct system (PDS).

Soil aeration below the building:


This measure helps to create a reduced pressure, with respect to the building, under the foundation slab. This method is somewhat complex but proves very effective, and is mainly recommended when the building is planned to have living spaces in contact with the soil. Radon is drained away by the use of actively or passively ventilated, perforated, 10 cm diameter pipes laid under the foundation slab.

Air circulation under the house:


A rather rare measure in newer buildings is the construction of a cavity space under the foundation slab in buildings without a basement. This cavity space is then ventilated or vented either passively, by judicious placement to the prevailing wind direction, or actively, by means of a ventilator.

Remedial measures for existing buildings:

If appropriate measurements have shown that the average radon concentration over one year is greater than 300 Bq/m3 in an existing building then radon protection measures should be initiated. The most suitable remedial method depends strongly on each individual case and should be clarified by a qualified radon consultant. Important: Subsequent to each remedial radon treatment, there is an obligatory control measurement!

Sealing the building sections that come into contact with the soil:


A continuous foundation slab and air-tight conduits for cables, water, waste water etc. can also be realised later. These seals prevent the ingress of radon from the subsoil. In many cases, however, these improvements are not sufficient and have to be complemented by further measures.

Mechanical ventilation:

Mechanische Ventilation

There is the possibility to install a ventilator in the cellar so as to create an adequate air exchange. If the whole building is mechanically ventilated by a controlled ventilation of the living space, care must be taken that the fresh air intake from outdoors is located at least 1.5 meters above ground level.

Reduced pressure system under the foundations (radon wells):


The possibility exists to selectively ventilate the ground air beneath the foundations by a so-called radon well. For this, a hole is drilled through the foundations and a shaft (ca. 0.5 x 0.5 meters) is excavated. The ground air is then carried away out of the shaft by a ventilator through a discharge pipe.

In most cases, suction at one place suffices (for example in the center of the house or in a room with a high radon concentration).

Last modification 20.08.2018

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Radiological Risk Section
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