The data used in the Groundsure report is known as the Radon Potential dataset, a definitive map of radon affected areas, created jointly by the British Geological Survey and UK Health Security Agency (UKHSA – formerly known as Public Health England). It uses long-term radon measurements made in over 560,740 homes in England and Wales, combined with geological map data. It shows the estimated percentage of dwellings exceeding the Radon Action Level.
Properties are considered to be in a radon affected area when more than 1% are above the recommended action level (200 becquerels per cubic metre (200 Bq/m3)). The UK Health Security Agency recommends that radon levels should be reduced in homes where the annual average is at or above this level.
The highest radon reading within the buffer/site outline is provided.
Risk bandings
- Less than 1%
- Between 1% and 3%
- Between 3% and 5%
- Between 5% and 10%
- Between 10% and 30%
- Greater than 30%
Data source: British Geological Survey and UK Health Security Agency
Data update schedule: Quarterly
This data was updated in December 2022 for the first time in about 10 years. It meant that some areas previously classed as not affected by radon, are now in a radon affected area.
This data is the highest resolution radon dataset available for the UK, produced to a 50m accuracy. This data has been pre-buffered to account for the relative accuracy and other uncertainties, so no additional buffering on site is required. The findings of this section should supersede any estimations derived from the Indicative 1km Atlas of Radon in Great Britain commonly used in local authority searches.
What is Radon?
Radon is a radioactive gas that we can't see, smell or taste. You need special equipment to detect it. It comes from the natural breakdown of uranium in soil, rock, and water and gets into the air we breathe. Radon typically moves up through the ground to the air above and into the home through cracks and other holes in the foundation, and become trapped inside without ventilation. Radon levels inside a building can fluctuate depending on air pressure. It is for this reason that 3 month radon tests are recommended.
Radon and conveyancing
During the conveyancing process, certain documents are used to ask questions about radon gas. These commonly include the CON29 Local Authority search and the TA6 Property Information Form which is completed by the seller.
Radon appears under section 3.14 of the CON29, and the question may be posed in different ways, but essentially it is asking whether the property is in a radon affected area, as identified by The UK Health Security Agency. The data commonly used in the CON29/local authority search is freely available and is accurate to 1km. It is common for the CON29/local authority search to show a higher level of radon than the Groundsure report. The Atlas is designed to provide a large-scale overview of possible radon issues in an area and not used as a property specific assessment.
Where there are discrepancies, the Groundsure report should be relied upon as it uses property specific data.
CON29/Local Authority Search vs Groundsure
Example data in a CON29 using the 1km Radon Atlas:
The 1km Atlas is showing the percentage of homes in the brown squares that may be affected by radon is estimated to be between 5% - 10%.
Example data in a Groundsure report for the same location:
If we take the centre point of the map, this shows no data which means less than 1% of properties are affected, indicating they are not within a radon affected area.
The second document is the TA6 Property Information Form. The TA6 covers the following in sections:
- 7.4 has a radon test been carried out on the property - a simple yes / no tick box. If yes, a copy of the report is requested, as well as asking if the test result was below the recommended action level.
- 7.5 then asks where any remedial measures undertaken on construction to reduce radon gas levels in the property.
Thirdly, and the most precise way of identifying if a property is in a radon affected area is through the environmental search. All Groundsure’s environmental searches contain property specific radon information.
How does Radon enter a building?
Radon, because it is a gas, is able to move through spaces in the soil, or fill material around a home or workplace's foundation. Most buildings tend to operate under a negative pressure - this is especially true in the lowest portions of the building and during the heating season. This negative pressure acts as a vacuum that pulls soil gases, including radon, into the lower level of the structure.
Some causes of negative vacuum are:
- Heated air rising inside the building (stack effect).
- Wind blowing past a building (downwind draft effect).
- Air used by fireplaces, wood stoves, and furnaces (vacuum effect)
- Radon can enter a building through the floor and walls -- anywhere there is an opening between the building and the soil.
- A basement, of course, provides a large surface area that contacts soil material.
Once radon enters a building, it moves freely throughout the air indoors, where people can breathe it into their lungs.
Radon moves by diffusion and natural air movements, so it can be distributed by mechanical equipment such as a forced-air ventilation system. As radon moves away from a building's foundation or other entry points, it mixes (and is diluted) into a greater volume of air. Additionally, more dilution often occurs in the upper levels of the building because there is more fresh air ventilation.
Measuring Radon - residential dwellings
We recommend that UKRadon is used for the testing. The most accurate testing method is done over a three month period. They will post out 2 detectors which need to be placed in a living area such as the lounge and an occupied bedroom. The amount of radon varies over time and from room to room in a home.
- Three month test - £52.80 inc VAT (as of September 2023)
- Two detectors to be placed in a living area and an occupied bedroom
- UKRadon then analyse the results once posted back
Measuring Radon - commercial premises
Work environments vary greatly in size and nature, as such the number of detectors required will vary. We recommend using this guide.
The detectors can be purchased directly with UKRadon.
If speed is a priority, a radon bond/retention may be set up.
Radon bond
A radon bond is an agreement between both the buyer and seller of the property come to. It involves solicitors on both sides agreeing on a 'radon bond' wherein a sum of money from the purchase price, agreed upon by both parties, is retained by the solicitor for a set period of time whilst testing is carried out. - Usually between £500 and £2,000
Radon and new builds
Building Control require new builds (and extensions in radon affected areas) to have radon protection incorporated into the design and build:
- For properties with less than 3% above the action level no radon protective measures are required,
- Properties with between 3 and 10% above the action level require basic radon protective measures,
- Properties with greater than 10% above the action level full radon protective measures are required.