Double-sided tape for gas-resistant membrane joints. Use with radon and hydrocarbon barriers. High-adhesion lap tape.

Detailing strip for critical junctions. Available in 300mm width. Ideal for detailing in damp protection and hazardous ground gas protection systems.

Top hat collars for sealing around service pipe penetrations. Compatible with gas, DPM and vapour membranes.

Radon, radon, radon, radon gas, BR211, Agrement, BBA, BDA, blok 400

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Third party accreditation (IAB certificate 05/0214) Conforms to the specification requirements of BR 211:2023 UKCA UKNI CE to EN 13967:2017 Visqueen certified with Quality Management System ISO 9001:2015 Visqueen certified with Occupational Health and Safety System ISO 45001:2018 Visqueen certified with Environmental Management System ISO 14001:2015

Visqueen RadonBlok 400 is used to prevent the ingress of radon in both basic and full radon protection areas. The membrane can be positioned within the ground floor construction either above or below the structural floor. The product is not intended for use where there is a risk of hydrostatic pressure.

Visqueen RadonBlok 400 should be stored horizontally, under cover in its original packaging. Care should be taken when handling the product in line with current manual handling regulations.

Visqueen RadonBlok 400 should be installed on a smooth continuous surface e.g. grouted beam and block floor, a compacted blinding layer e.g. 50mm thick sand blinding, or smooth concrete blinding. The substrate should be free from irregularities such as voids or protrusions. The membrane can be cut with a sharp retractable safety knife or robust scissors. When installing the membrane in demanding site conditions, use Visqueen NF-150 Lap Tape in place of Visqueen Pro Single Sided Tape.

Visqueen RadonBlok 400 should be loose laid on the substrate. The membrane should be clean and dry at the time of jointing. It should be overlapped by at least 150mm, bonded with Visqueen RadonBlok Double Sided Tape and sealed with Visqueen Pro Single Sided Tape. Alternatively lap joints can be heat welded to achieve an effective seal. Welded lap joints can be less than 150mm provided the joint integrity is not compromised. Airtight seals should be formed around all service entry points. Visqueen Preformed Top Hat Units should be used for sealing service entry pipes. The base of the top hat and the upstand should be bonded using Visqueen RadonBlok Double Sided Tape and sealed with Visqueen Pro Single Sided Tape. The upstand should be secured with the supplied jubilee clip. Alternatively VisqueenPro Detailing Strip or Visqueen NF-Detailing Strip can be used to seal service entry points. The upstand should be secured with a jubilee clip. Forming an effective barrier to radon may give rise to complex three-dimensional detailing where, it is recommended Visqueen Preformed Units are used e.g. corners. Alternatively Visqueen Pro Detailing Strip or Visqueen NF-Detailing Strip can be used to seal awkward junctions. If the membrane is punctured or perforated a patch of the same material should be lapped at least 150mm beyond the limits of the puncture and bonded with Visqueen RadonBlok Double Sided Tape and sealed with Visqueen Pro Single Sided Tape. Alternatively a patch can be formed using Visqueen Pro Detailing Strip or Visqueen NF-Detailing Strip and lapped at least 150mm beyond the extents of the puncture. Long periods of exposure to ultraviolet light will reduce the effectiveness of the membrane. The membrane should be covered by a protective layer immediately after installation to prevent damage from following trades, ultraviolet light, etc. Care should be taken to ensure that the membrane is not punctured, stretched or displaced when applying a screed or final floor covering. A minimum thickness of 50mm screed is recommended. When reinforced concrete is to be laid over the membrane the wire reinforcements and spacers must be prevented from puncturing the membrane. Where there is a high risk of potential damage, the membrane should be covered with Visqueen TreadGUARD protection, screed, or other approved protection material before positioning the reinforcement. When used in full radon protection areas, a Visqueen Radon Sump or subfloor ventilation system maybe required.

When taping joints, it is recommended that Visqueen RadonBlok 400 and all associated system components should not be installed below 5°C.

Where ground gas protection is required to BS 8485:2015 + A1:2019, use Visqueen Gas Barrier or Visqueen Gas Barrier NF-400 systems. To assist build sequencing, Visqueen Zedex CPT DPC is available for radon protection through the wall constructions. For additional detailing information, contact Visqueen Technical Services +44 (0) 333 202 6800. The information in this datasheet was correct at the time of publication. It is the user’s responsibility to obtain the latest version of the datasheet as it is updated on a regular basis. The information contained in the latest datasheet supersedes all previously published editions.

Refer to the Visqueen RadonBlok 400 safety datasheet (SDS)