20 mm Hi-Viz Cavity Drain Membrane for Waterproofing Basement Floors.

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Price incl. VAT
(10 items in stock)

Use Wykamol CM 20 mm Hi-Viz cavity drain membrane to waterproof basement floors. The yellow tanking membrane stands out from black butyl tapes. The contrast makes the joint seals easier to check. 

What is a 20 mm Hi-Viz Cavity Drain Membrane?

The bright yellow membrane is an HDPE barrier with 20 mm stand-off studs at 50 mm centres. The stand-off studs create a drainage space to contain water seepage. The cavity beneath the membrane has a volume of 14 litres per square metre. The large gap is ideal when tanking floors prone to constant moisture intrusion or high water table levels.

The 40 sqm tanking membranes are robust and durable. Wykamol 20 Hi-Viz will last the design life of the building. HDPE is rot-proof and resistant to alkalies, bacteria and fungi. Use the membrane to waterproof basement floors and other below-ground bases that require a cavity drain system. 

How do you use 20 mm Hi-Viz Membranes to Waterproof Basement Floors?

Set out drainage channels. Fit sump chambers where necessary. Treat freshly laid concrete with an anti-lime sealer to prevent free lime from leaching. Lay the roll of the membrane as you would lay Lino. Overlap the joints using the 100 mm wide stud-free flanges or ensure a 3-stud interlock. Use waterproof tape to seal all joints and floor-to-wall junctions. Finish with a concrete pour or a 65 mm screed.

Type C Waterproofing with Cavity Drain Systems.

Basement waterproofing membranes form part of a sealed cavity drain tanking system. The system must manage and dispose of water behind the membrane as per BS 8102: 2022. The Wykamol CM 20 mm cavity drain membranes are BBA approved for Type C waterproofing.

We stock the yellow CM 20mm hi-vis waterproofing membrane in 2 m x 20 m rolls. The bright yellow tanking barrier lightens dim workspaces. The membrane is easy to cut and trim using a sharp blade. Twistfix offers expert advice on cavity drain membranes. You can buy them online at low trade prices.

  Hi-Viz 20 mm Cavity Drain Membrane.   Data
  Material.   HDPE.
  Sheet Thickness.   1 mm.
  Membrane Height.   20 mm.
  Water Void Capacity.   > 14.61 l//m².
  Weight.   1 Kg/m² .
  Water tightness at 60 kPa.   > 24 hours.
  Working Temperature.   - 50° C to + 80° C.
  Softening Temperature.   126°C.
  Mean Compressive Strength.   165 kN/m² .

Delivery options are only available for delivery to mainland UK (excluding Scottish Highlands, Scottish Islands, Channel Islands, Isle Of Man Northern Ireland and Eire). Delivery to Scottish Highlands, Scottish Islands, Channel Islands, Isle Of Man, Northern Ireland and Eire are limited to 20kg and are available at a Premium rate. Please contact us on or via our help line if delivery is required outside these areas. Alternatively select ‘World-wide Delivery’ and a member of our sales staff will contact you regarding your options and costs.


We offer for the mainland UK , as standard, a FREE delivery service on all orders having a value greater than £200.00 (excluding VAT). For orders having a value less than £200.00 (excluding VAT) a carriage fee of £8.50 + VAT will be levied. Goods will be sent by a national carrier on their 1-2 working day standard service. Customers must understand that delays can always happen while their order is with the courier, for this reason we can not guarantee your order will be with you next day.

It is important that the customer ensures that all the delivery details are correct and that the customer or someone acting for the customer is able to sign for the delivery. Twistfix accept no liability for failed deliveries as a result of incorrect delivery details or the absence of any authorised signatory. Twistfix will attempt delivery to the recipient between the hours of between 8am and 6pm. If no one is available to receive the delivery an attempt may be made to leave the item with a neighbour. Alternatively the carrier may return the item to the sorting office and leave a calling card at the recipient's address to advise of the attempted delivery. It is the responsibility of the customer to arrange to collect the item from the depot or to arrange re-delivery with the carrier. Further information regarding Delivery can be read at our Terms & Conditions.


Items returned and received in their original condition and packaging within 14 days of delivery will be accepted for exchange or refund subject to a 20% restocking fee. You will be responsible for the shipping costs incurred in returning the goods and should ensure the items are adequately insured while in transit to us. You should email to request to return items.

Where the goods are being returned because they are faulty or are not the goods that were ordered then, subject to the goods being returned in re-saleable condition, Twistfix will refund the cost of return shipping. Further information regarding Returns can be read at our Terms & Conditions.