The ground is the main source of radon.

The aim of remedial work is to reduce radon levels as low as possible. There are several methods that can be used to reduce high radon levels. Have you already tested? Use our interactive tool to help you decide whether you need to reduce your radon level and if so how.

Remedial methods

Some simple actions such as sealing around loft-hatches, sealing large openings in floors and extra ventilation do not reduce radon levels on their own. When combined with other effective measures, they can improve the reduction of radon levels. Completely sealing floors is difficult and can cause rot in wooden floors. The diagram below is intended as a guide. The Environmental Health Department of your local council may be able to offer advice. For levels in excess of 1000 Bq m-3 you may wish to contact UKHSA for advice.


Floor type Solid
Radon level*
(Bq m-3)
Under 500
Over 500
Under 500
Over 500
Recommended solutions, best first Radon sump
Positive ventilation
Radon sump Natural under-floor ventilation
Positive ventilation
Mechanical under-floor ventialtion
Natural under-floor ventilation

For houses with mixed floor types, a combination of the above can be used.
*The level of 500 Bq m-3 is an approximate guide.

Remedial costs

Costs depend on many factors including the complexity of the building and whether any of the work can be done by DIY. The table below shows approximate costs for measures installed by a contractor (apart from the DIY sump).

Remedy Typical cost Normal range
Active sump (with fan) £800 Up to £2,000
Active sump (DIY) £300 Up to £700
Passive sump (without fan) £450 Up to £1,000
Natural under-floor ventilation £200 Up to £600
Active under-floor ventilation £700 Up to £1,500
Positive ventilation £550 Up to £1,000

Average prices above derived from data between 2007 - 2017.