https://www.gov.uk/government/publications/site-preparation-and-resistance-to-contaminates-and-moisture-approved-document-c

Building Regulations

Comply with UK Building Regulations, particularly Approved Document C, which addresses site preparation and resistance to contaminants including radon.
Ensure all construction practices adhere to these regulations to mitigate radon ingress effectively.

Diagram- Corner detail for an installed radon membrane Figure Reference:

2. Sealing Penetrations

Use proprietary "top hat" seals where the membrane is penetrated by service pipes.
Double-sided tape is first placed around the service pipe, then the “top hat” is installed, and the clip tightened to ensure a gas-tight seal.
Apply double-sided sealing tape between the radon membrane and the “top hat”.
Diagram- Blinding granular fill to reduce the risk of damage to the radon membrane Figure Reference:

3. Membrane Placement

Ensure the membrane is laid across the entire floor and up the external walls.
Avoid damage to the membrane during installation
and concrete pouring. Carry the membrane at a lower level to the finished floor across the rising wall to protect it during power floating.

4. Sealing and Protection

Seal all tears in the membrane, no matter how small.
Laps must be fully sealed with appropriate tape to ensure gas-tightness.
Diagram- Top hat' seal around a service pipe

Protect any exposed areas of the membrane during construction until permanent cover is in place.
Ensure the pipe terminal from the radon sump is identified and permanently marked.

5. Barrier Protection

Utilize blinding granular fill to reduce the risk of damage to the radon membrane.
Provide precautions at wall-floor junctions and movement joints to minimize differential movement between walls and concrete slabs.

6. Settlement Accommodation

Install the membrane with an upstand at the wall/floor junction to accommodate a small amount of settlement if necessary.
If no settlement is expected during the building's lifecycle, the membrane can be laid flat as per the certification requirements.

7. Gas-tight Seals

Ensure all joints and service penetrations are adequately sealed, using gas-tight seals around water pipes and other penetrations.
Use double-sided radon-resisting tape to seal laps in the membrane.

Diagram- Double-sided radon-resisting tape being used to seal laps in radon membrane

Diagram- Example of gas tight seals

8. Ensuring Membrane Fitness for Use

Radon membranes, generally made of LDPE (Low-Density Polyethylene), can often serve as damp-proof membranes in ground floor construction.

Ensure membranes are independently certified for radon protection by an approved body (e.g., NSAI-IAB).

Table HR1: Minimum Performance Levels for LDPE Radon Proof Membranes

9. Installing Radon Sumps

https://www.housebuild.com/construction/building-regulations/building-regulations-and-other-guidance/radon/radon-sumps

Purpose:

A radon sump system helps to vent radon gas from beneath the building, thereby reducing its concentration indoors.

Design:
- Location: Install the sump centrally under the building's foundation to maximize effectiveness.
- Pipework: Use perforated pipework around the sump to create a pathway for radon gas to enter the sump.
Installation:

i) Location and Placement:

For typical houses with floating floors, the radon sump is installed beneath the floor slab within the permeable granular fill material.
A single radon sump effectively influences an area up to approximately 250 m², extending its impact up to 15 meters from the sump when clean granular fill is used.
The effectiveness may be hindered by obstructions beneath the floor slab, thus requiring free airways in rising walls or separate sumps for different compartments.
To ensure sufficient free airways, a gap equivalent to 12,500 mm² per meter run of wall is recommended.

ii) Extraction Pipe:
Diagram- An extraction pipe from a radon sump

A 100-110 mm diameter pipe is laid horizontally from the sump to the outside of the house.
It is crucial to seal all pipe joints and where the pipe penetrates the rising wall to prevent drawing in outside air.
The pipe should be covered to prevent vermin or rain penetration, either at ground level or a higher level that avoids obstruction.
Alternatively, the pipe can be extended vertically and capped in the attic space.

iii) House Location:

Each house requires a separate sump and an associated extraction mechanism.
Proprietary sumps are installed in hardcore material.
Diagram- Typical location in a single house for a radon sump
Diagram- A proprietary sump installed in hardcore

Fan Connection:

In cases where radon levels are detected to be high, the extraction pipe can be extended, and a fan fitted to enhance radon mitigation.
Pipe terminals must be clearly marked to indicate their function to avoid misuse.
A layout for fan connection should be considered during the installation phase.

Important Considerations:

Proper sealing of pipes and joints.
Provision of adequate free airways.
Clear marking of pipe terminals.
Regular radon level monitoring.

By adhering to these guidelines and maintaining regular checks, the risks associated with radon can be significantly mitigated, ensuring a safer living environment.

10. Positive Ventilation Systems
Diagram- : How positive ventilation work

Installing a positive ventilation system is an effective way to improve indoor air quality by ensuring a continuous supply of fresh air into a building while expelling stale air. Here is a step-by-step guide to help you install a positive ventilation system:

Fresh air enters the roof space from outside (1). It passes through the fan unit (2), and disperses through the dwelling (3). Some air escapes to outside through leakage all over the structure (4).

Some air is forced through the floor, stopping radon entry (5).

Benefits of Positive Ventilation Systems:

Fresh Air: Introduces fresh air into the home, diluting radon levels.
Air Flow: Reduces the flow of radon from the ground.

System Effectiveness:

Suitable for Homes with Radon Levels: Up to around 500 Bq m-3.
Best for: Well-insulated, draught-free homes, particularly bungalows.

Typical System Components:

Fan: Installed in the roof space, connected to a ceiling vent.
Vent: Usually placed in a central hallway or stairwell.
Duct: Flexible duct connects the vent to the main unit.
Filter: Ensures clean air.
Optional Heater: Some units include a heater.
Quiet Operation: Fans are designed to be quiet.

Installation:

Quick and Simple: Typically takes a day or less.
Cost: Ranges from £550 to £1000.
Energy Efficiency: Fans consume similar electricity to an energy-efficient light bulb.

Additional Benefits:

Improves Air Quality
Reduces Condensation

Guide to Installing Radon Barriers and Sumps in New Builds: