Section 5.1.3

Radon Barriers

Damp proof membrane and damp-proof course are designed to prevent damp rising from the ground and into the property. It also plays a vital part in preventing ground gases from entering the property. Attention to detail is critical to its success. For sites classed as Amber 2, specialist contractors and independent validation is required.

  • Preparation for the installation of the DPM must be complete before commencement.

  • Block and beam fully grouted with no gaps around the penetrations.

  • Free from debris and other materials which could puncture the membrane.

  • Gas damp proof membrane laid across the block and beam.

  • Pulled taut with limited folds and joints.

  • Ballast can be carefully placed on top of the membrane to prevent movement.

  • Damp proof membranes require sealed laps of 300mm or as per the manufacturer’s recommendations.

  • Gas membranes require the laps to be sealed.

  • At party walls the membrane must form within the cavity to a minimum depth of 450mm.

  • This is to comply with Robust details.

  • On this occasion, shuttering has been provided to the opening and filled with a lean mix concrete.

  • Cap off the pipe work to ensure no foreign material can enter the pipe work.

  • Pipework has been marked up in concrete for identification.

  • Penetrations require an appropriate seal.

  • Seals need to be complete around both base and pipe.

  • Approved tape should be applied to the membrane the pipe work or ducting penetration.

  • Mechanical fixing used around the pipe/duct to secure the “top hat”.

  • Gas membranes must be cut flush with the external face of the brickwork.

  • A cavity tray must be provided, and weep holes installed to allow moisture that enters the cavity to egress.