To comply with the building regulations 'BR211 guidance on protective measures for new dwellings', the following approach should be adopted.
The requirement of a radon barrier is to prevent any radon gas entering a property. To ensure that this is achieved, it is necessary to follow some important, but straight-forward practices. Ideally, the use of a proprietary barrier is preferred to ordinary polythene, as it is normally of a superior quality material. The barrier must cover the whole footprint of the building including any external or internal cavities. Care must be taken to ensure that the barrier is laid on well blinded hardcore, or cleaned and swept suspended floor, and should be inspected for damage prior to covering with slab or screed.
Any damage to the barrier should be repaired using additional barrier, ensuring a 150mm lap. Where strips of barrier are incorporated into the external and internal walls at commencement, they must be suitably protected for the duration of the build until the main carpet of the barrier is installed. All laps should be sealed with butyl jointing tape, not adhesive tape, normally 50mm wide. The barrier should be as dry and clean as possible before applying the butyl tape. All penetration for services and drains should be sealed using preformed top hats, again sealed to the barrier with butyl tape. Where there are pile caps or stanchions, advice should be sought.
Corners can present difficulties, and again, products are available to assist in achieving the integrity required.A recent study has shown that a significant number of barriers failed to be radon proof, and with houses being tested for radon at conveyancing, it is essential that best practice be adopted. The full requirements for compliance with the building regulations can be found in the BRE document 'Radon: guidance on protective measures for new dwellings BR211'.