Visqueen Ultimate HC Block

This new Visqueen product replaces the Visqueen GX flexi – which is now being phased out.

The ultimate Methane & VOCs’ vapour barrier.

■ Conforms to CIRIA C748 and BS8485:2015
■ Excellent VOC (vapour) & methane barrier resistance
■ Utilises Visqueen’s Advanced Barrier Technology
■ Exceptional flexibility and puncture resistance
■ Comprehensively tested and validated test results
■ Outstanding welding characteristics, saving time and costs


Visqueen Ultimate HC BLOK is a highly flexible 0.5mm thick coextruded membrane designed to comply with current guidance on Volatile Organic Compounds (VOCs) vapours and ground gases. Manufactured using Visqueen’s advanced membrane technology and drawing on our extensive knowledge and expertise in gas
protection, Visqueen has developed a new flexible barrier membrane suitable in brownfield applications that are affected by aggressive chemicals (vapour phase) such as such as Naphthalene, Benzene, Toluene, Ethyl Benzene and Xylene (BTEX).

The product is available in large roll formats to minimise jointing and quick installation times. The membrane is gold and white, 2.44m x 41m x 0.5mm (100m²), in single wound roll format and packaged in a white outer wrap. The membrane should be installed gold side up.


Visqueen Ultimate HC BLOK is suitable for the following applications
■ VOC/Hydrocarbon (gaseous phase) contaminated sites in accordance with CIRIA C748
■ Carbon dioxide and methane sites in accordance with BS8485:2015
■ Radon affected sites in accordance with BRE211:2015
■ Damp protection in accordance with Building Regulations part C Due to a diverse range of applications, site conditions and variations in attack chemicals we strongly advise contacting Visqueen’s technical department for correct specification and detailing – 0333 202 6800

The innovative Visqueen’s advanced barrier Technology

1. An advanced gas barrier structure
2. Superior physical and chemical resistant properties
3. Easy & rapid welding
4. Flexibility for uneven ground contours
5. Good environmental stress crack resistance
Advanced barrier technology utilises Visqueen’s extensive
manufacturing technical expertise and experience to ensure buildings
and occupants are safe from hazardous ground gases and VOCs.

System Components:

■ Visqueen GX Double Sided Bonding Tape
■ Visqueen Gas Resistant Lap Tape
■ Visqueen Surface DPC Fixing System
■ Visqueen GX DPC
■ Visqueen GX Top Hat Units
■ Visqueen Detailing strip
Please note that the membrane can be welded as a preferred
alternative to using tapes.


Visqueen Ultimate HC BLOK and ancillary components must be installed in accordance with the recommendations of CIRIA C748 and BS8485:2015. The membrane should be installed on a blinded or smooth surface allowing adequate overlap for jointing between the sheets and avoiding bridging (i.e. areas of unsupported membrane).
In areas where high levels of unsupported membrane such as settlement applications occur it is recommended that Visqueen Ultimate GeoSeal is used.
Visqueen Ultimate HC BLOK is normally installed above the concrete slab (vented void) but can be used below the slab in certain conditions. Please contact Visqueen for further information on foundation types and membrane suitability – 0333 202 6800 Technical Department.



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