Home » Your Council » Building Control » Radon gas

Radon gas

« Back

Radon Gas

What is Radon Gas?

Radon is a colorless, odorless radioactive gas. You can't feel it, smell it, or see it, and you can only detect it using very sophisticated scientific equipment.

Where does Radon come from?

Radon is formed in rocks where uranium and radium are present - particularly granite. The gas seeps through cracks in the rocks and soil and normally disperses into the atmosphere.

Where is Radon found?

Radon is found in all parts of Northern ireland, however it is at its greatest concentrations mainly in the south and west, with small isolated areas in the north east.

What effect does Radon have?

Where buildings are constructed above certain types of ground, radon can percolate up through the rock, collect and build up within the building to a level, which could be a risk to health. Radon is considered to be a major source of radiation, exposure to this radiation is known to cause cancer and inhalation of radio-active gas significantly increases the risk of lung cancer.

How can you protect against Radon?

The best way to avoid the effects of radon is to take measures to prevent the gas from entering your house. The two most common means by which this can be done is:

Radon Membrane: Lay a sheet of material that the radon cannot pass through over the ground beneath the house. This can be an impermeable membrane, such as 1200 gauge polythene. A membrane will reduce the radon level by approximately 50%.

If an impremeable membrane is to be effective, it is very important that there are no gaps at the edges, or where service pipes enter the house. Measures should be taken to ensure the membrane is not ruptured should the floor slab settle.

Radon Sump: This is a void created beneath the house, with a pipe to the outside, to prevent the radon getting into the dwelling. A sump will reduce the radon level by approximately 90%, if fitted with a continuous running fan. Under the current regulations there is no requirement to fit the fan, but it enables the homeowner to initiate sub floor de-pressurisation in the future, if it is discovered that the Radon level in the dwelling is high.

Timber Floor Construction

Timber floors are not encouraged in areas effected by Radon as they offer little resistance to the passage of Radon. To overcome this, we recommend all gaps in the flooring be sealed and the provision of a membrane in the sub-floor (with appropriate measures to prevent rupturing). The air void below the floor should be ventilated. In addition to this, in certain areas a sump is needed below the floor.

Requirements of the Regulations

Since 1994, the Building Regulations (Northern Ireland) requires ....

..."measures shall be taken to prevent or limit the ingress of Radon from the ground into any dwelling situated in any zone marked on the map"....

The regulations relating to Radon apply to the following:

New Dwellings

  • Extensions to existing dwellings
  • Extensions or alterations to existing dwellings which already have Radon preventative measures.

If you need any further information on Radon Gas, please telephone:
0 28 4461 0829 and speak to the Building Surveyor for your area. You may also want to view the Health Protection Agency's information on Radon.



Gregory Bradley
Building Control
Downshire Civic Centre
Downshire Estate
Ardglass Road
BT30 6GQ
T: 0 28 4461 0829
F: 0 28 4461 0845