What Is Radon? How It Enters Buildings and How to Manage It.
Radon is a naturally occurring gas that is present in many parts of the UK and across the world. It is invisible, odourless and tasteless, which means it can exist in buildings without being noticed.
While radon is a natural part of the environment, understanding how it behaves and how it enters buildings is important, particularly when designing or improving the building envelope.
What Is Radon?
- Radon is a radioactive gas that forms when uranium in soil, rock, and groundwater decays over time.
Outdoors, radon is usually diluted and does not pose a significant risk. However, in enclosed spaces such as buildings, it can accumulate to higher concentrations if not properly managed.
Because it cannot be seen or smelled, radon is typically only identified through specialist testing.
Why Radon Matters in Buildings
Radon becomes a concern when it builds up inside a property over time.
The level of radon in a building depends on several factors, including:
- the underlying ground conditions
- how the building is constructed
- the level of airtightness
- ventilation strategy
Modern construction methods, which focus on improving airtightness and energy efficiency, can reduce uncontrolled air movement, but also make it more important to manage how gases and air enter and leave the building.
How Does Radon Enter a Building?
Radon typically enters buildings from the ground beneath them.
It can pass through:
- cracks in concrete floors
- gaps around service penetrations
- joints between floor slabs and walls
- construction joints and cavities
As warm air rises inside a building, it can create a slight pressure difference that draws gases from the ground into the structure.
This process is sometimes referred to as the “stack effect.”
Radon and the Building Envelope
The building envelope plays a key role in controlling how air and gases move through a structure.
Uncontrolled air leakage paths can allow radon to enter, particularly at:
- floor-to-wall junctions
- service penetrations
- poorly sealed construction details
Improving the continuity of the building envelope can help reduce unintended air and gas movement from the ground into the building.
Managing Radon in Construction
There are several strategies used in construction to help manage radon:
- radon barriers or membranes at ground level
- careful sealing of junctions and penetrations
- sub-floor ventilation systems
- appropriate building design based on local radon risk
In many cases, radon protection is considered alongside airtightness strategies, as both aim to control air movement through the building envelope.
The Role of Airtightness and Membranes
A well-designed airtight layer can help limit the pathways through which gases, including radon, can enter a building.
By sealing:
- cracks
- joints
- penetrations
membranes and airtightness systems can contribute to a more controlled internal environment.
Products such as liquid-applied membranes can be particularly useful in complex areas, where achieving continuity with traditional materials may be more difficult.
A Balanced Approach
It’s important to note that managing radon is not about eliminating it, but about controlling its movement and preventing build-up indoors.
This is typically achieved through a combination of:
- good design
- appropriate materials
- ventilation strategies
- and, where necessary, testing
Contact us if you’re working on a project where ground gases, airtightness, or building envelope performance are a consideration. Our team is here to help.