Changes to UK Radon Maps – what it means for your development

Radon is formed from the decay of Uranium and Thorium in rocks and soils, and is a radioactive gas. Inhalation of high concentrations of Radon has been strongly linked to lung cancer, and Radon is considered to be the second-most frequent cause of lung cancer after cigarette smoking.

The radon level is very low outdoors but can accumulate indoors due to the high density of Radon gas in comparison with air.

How Do We Mitigate Radon?

The Radon Potential data classifies areas based on their likelihood of a property having a radon level at or above the Action Level. The Radon Action Level is currently set at 200 Bq/m3. The Radon Potential data is presented as a percentage of properties affected by Radon and are:

  • Less than 1% of properties affected
  • Between 1% and 3% of properties affected
  • Between 3% and 5% of properties affected
  • Between 5% and 10% of properties affected
  • Between 10% and 30% of properties affected
  • Greater than 30% of properties affected

The levels at which protection measures are required varies across the UK, with initial trigger levels split between England & Wales and Scotland. 

In England and Wales: 

At a level of 3% or less mitigation measures are not required. At a level of >3%Building Regulations require Basic Radon Protection measures to be installed. At a level of 10% or more, Full Radon Protection is required. 

In Scotland:

At a level of 1% or less mitigation measures are not required. At a level of >1%Building Regulations require Basic Radon Protection measures to be installed. At a level of 10% or more, Full Radon Protection is required. 

Contrary to guidance in England and Wales, properties in Scotland in the range 1-3% require Basic Radon Protection Measures.

Basic Radon Protection will comprise the installation of a Radon Protection Membrane across the floor slab, depending on the foundation construction type adopted.

Where Full Radon Protection measures are required, this will likely comprise the installation of a Radon Protection Membrane across the floor slab and ventilation measures, depending on the foundation construction type adopted.

Any protection measures required will need to be set out in a site-specific standalone document, by a qualified Environmental Consultant.

Map showing Radon protection areas

Radon Map – Recent Update

The UK HSA launched a new radon map on 01/12/2022.  The new map has resulted in Radon classifications in some areas changing to a level where Radon protection is required where previously it was not, or to a higher level of Radon protection being required.

You can check whether the Radon Classification for site has changed by checking on the UKRadon website and entering the site postcode, however this search is only suitable for single dwellings (no larger than 25m in size) UKradon – UK maps of radon

If the site/land is for redevelopment, a GeoReport provide by the BGS should be obtained BGS Shop · Radon : England and Wales GeoReport.

NHBC Radon Requirements 

From the 1st December 2022 onwards, all sites registered with the NHBC will have been assessed against the updated radon maps. If you’re site was assessed by an environmental consultant prior to 1st December 2022, the Radon Risk may have changed, and this will need to be reassessed.

From 1st February 2023 plots commencing construction with the NHBC will be required to have radon protection measures installed in accordance with the updated mapping.

The NHBC recommends that developments that have already commenced prior to the publication of updated mapping should discuss with the NHBC how best to comply with the higher level of protection that may be needed. To know if you’re site has been affected, order a BGS Map from BGS Shop · Radon : England and Wales GeoReport, or contact us for further advice and information.

Related Articles

Minerals Resource Assessment

MRA

Sustainable Solutions

Trees

Materials Management Plan

Trees