Wykamol CM20 Waterproof Floor Membrane (20mm Stud)

Wykamol CM20 Waterproof Floor Membrane (20mm Stud)

Wykamol Group | Basement Waterproof Membranes

Wykamol CM20 is a High Quality, 20mm Stud, Cavity Drain Basement Waterproofing Floor Membrane made from High Density Polyethylene (HDPE).

Wykamol CM20 Membrane is used as a high drainage capacity floor membrane and is generally specified where it is anticipated that there may be a risk of severe water penetration.

  Wykamol CM20 Waterproof Floor Membrane is supported by BBA Certification Certificate Number 18/5595.

Supplied in 2.07M x 10M (20M²) Rolls.


Wykamol CM20 Cavity Drain Floor Membrane

Wykamol CM20 Membrane is a Cavity Drain Waterproofing Membrane made from High Density Polyethylene (HDPE).

With its 20mm deep stud profile, Wykamol CM20 Membrane is used as a high drainage capacity floor membrane and is generally specified where it is anticipated that there may be a risk of severe water penetration.

Wykamol CM20 Membrane is suitable for Type C waterproofing while delivering a grade 3 environment to BS8102:2009 and NHBC Chapter 5.4.

Wykamol CM20 Membrane has a life expectancy of at least the design life of the building. It is inert and, therefore, non-polluting to drinking water, highly resistant to water, alkalies, saline solutions and organic acids, and not affected by minerals and hydro-carbons. It is also impervious to root penetration, is rot-proof, and resistant to bacteria, fungi and other small organisms.

Benefits & Features:

  • BBA Approved

  • Part of a Type C Cavity Drain Membrane System in Line With BS8102:2009

  • Gives a High Water Void Volume of 14 Litres/m²

  • Quick to Install - Easy to Roll Out Along Floors

  • Creates a Dry, Habitable Living Space in Areas Previously Suffering From Damp / Wet Conditions

  • Easily Cut Down Using a Sharp Blade

  • Waterproof, Salt Inhibiting, Root and Contaminate Resistant

  • Little or No Damage to the Existing Structure

  • Low and High Temperature Tolerance

  • High Grade Material

Technical Data:

Material High Density Polyethylene (HDPE)
Unit Weight 1kg/m²
Sheet Thickness 1mm
Stud Height 20mm
Colour Black
Water Tightness - 60 kPa; 24h (EN 1928) Pass
Working Temperature -50°C to +80°C
Softening Temperature 126°C
Tensile Strength MD (BS 12311-2) 416 N
Tensile Strength CD (BS 12311-2) 488 N
Resistance to Static Loading (BS 12730) >20 Kg
Compressive Strength (BS EN ISO 25619-2) 170 kN
Reaction to Fire (BS EN 13501-1 :2007+A1:2009) Class E
Type of Application Type V
Life Expectancy Lifetime of Structure


Wykamol CM20 Membrane should only be used on floors. Before the system is installed, the area must be assessed to determine what preparation is required:

All timber and other organic material must be removed to prevent risk of fungal or bacterial growth behind the System. If evidence of rot exists, this must be dealt with by a specialist contractor prior to installation of the system.

Brush the floor clean and remove any sharp protrusions. Fill all non-structural cracks above 1mm wide, all structural cracks should be repaired or treated.

New concrete should be treated with Platinum Lime Inhibitor which prevents free lime from the curing concrete being drawn out by ingressing water.

Drainage Requirements

When used in a full or part earth-retaining situation, the membrane system must be drained. To comply with BS 8102:2009, you must assume that the structure will be subjected to water ingress at some time.

Methods Of Drainage:

The drainage must effectively remove all water from below the membrane and take the water to a point of discharge such as a Sump Chamber or a form of safe natural drainage. Standing water can block the membrane with silt or lime scale so it is important for water to flow uninterrupted to the drainage point.

Wykamol Waterguard Drainage Channel

Wykamol Waterguard is placed at the wall / floor junction and collects water from behind the wall membrane and receives water at the wall / floor junction. Wykamol Waterguard is a designed method of removing water as it can interface with sump chambers, gullies, waste pipes etc.

It can also be maintainable by inserting either Flexible Jetting Eyes or Extended Jetting Eyes into the system. 

Installation Method:

It is very rare for water to pass through a solid concrete slab or concrete raft, but where the slab or raft is of questionable quality it is possible for water to pass through cracks in a poorly constructed floor. If the quality of the slab is questionable, Wykamol CM20 Membrane should be used as the floor membrane.

Starting at one side of the room, unroll the membrane with the studs down and cut to fit the room as one would a carpet. The next membrane width is rolled out so that the flanged edge overlaps onto the edge of the previous roll of membrane. Clean both edges.

Wykamol Membrane Tape is then applied to the high flat area between the first two studs at the edge of the previous roll of membrane with the backing paper still intact.

Check the two widths for alignment, with the flange covering the backing paper.

Starting from the end of the joint, remove the backing paper and press down on the joint sealing the two sections together. This process is repeated until all areas are covered. Seal the Wykamol CM20 Membrane to the up-stand of the perimeter drainage channel (i.e Wykamol Waterguard Channel) with Wykamol Corner Strip Tape.

Where the floor membrane is required to be jointed to horizontal DPC’s through internal and external walls, these joints should be sealed with Wykamol Membrane Tape. Ensure both surfaces are clean and dry before attempting to make these joints.

If there are any services up through the floor, the membrane can be cut and trimmed around them, and the gap filled and sealed using a high quality Hybrid Polymer Adhesive.

If necessary, a patch of membrane or plain DPC is laid over and sealed to the service with Wykamol Rope, and around its perimeter with Wykamol Membrane Tape.

It should be noted that protrusions through the floor slab/raft should be avoided wherever possible as they create weaknesses that allow unnecessary water ingress.

The specified floor finish can now be laid directly over the floor membrane, which must not be punctured by any fixings through the floor. When a timber floor finish is preferred you must allow an expansion gap around the wall edge.

Speak to the supplier of the floor finish to confirm the correct size of this expansion gap.

Data Sheets

Technical Data Sheet

Declaration of Performance (DoP)

BBA Certificate

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