Hydroduct® CF20

Hydroduct® CF20

GCP Applied Technologies Third party certifications:
  • BBA Agrément Certificate

    BBA Agrément Certificate

    Certificate type

High density polyethylene combined cavity former and vapour barriers for drained BS 8102:2009 Type C basement construction. Forming drained cavities horizontally & vertically.

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A range of high density, high strength, chemically resistant polyethylene drained cavity formers designed to reduce the risk of water ingress beneath floor screeds and between concrete and blockwork walls to form an efficient drained cavity to new and existing sub-structures.

When installed against the internal face of concrete floors and walls, Hydroduct® CF will provide a continuous drainage path which must link to the site internal drainage system. Not suitable for internal applications where no linking with the site drainage system is possible.

Hydroduct® CF forms part of a Type C structure (drained protection) as described in BS 8102.

The cavity formers are compatible with all cementitious, bituminous and polyethylene building materials.


Floor slabs should ideally be laid to falls to drainage gully or outlets. A flat slab is acceptable providing there are no adverse falls and low spots are infilled. Where surface irregularities exceed 5 mm, cut back and make good.


  • Vertical membranes should be installed before horizontal.
  • Vertical applications: Install in a continuous strip with dimples to the external wall. If horizontal laps are unavoidable, the upper sheet must be overlapped by the lower sheet, to ensure water is retained within the cavity.
  • Horizontal applications: Loose lay membrane with dimples to the floor and cut around any obstructions. Mechanically fix to substrate. Seal around column bases, obstructions, etc, by applying Hydroduct Strip 4000. Prime all substrates to receive Hydroduct Strip (other than CF membrane) with Bituthene® B1 primer to ensure full adhesion.

Fixing centres:

600 mm.


– Walls: Overlap all vertical joints:

  • Minimum 200 mm. (For CF 20).
  • Minimum 150 mm. (For CF 08).

– Floors: Interlock four dimples.


Seal all joints with Servitape double sided adhesive tape. Seal all penetrations through with Servijoint One DW sealant.

General information




High density polyethylene


2.0 x 20.0 m / roll

2.0 x 20.0 m

Uniclass 2015

Pr_25_57_65_60 Plastics sheetsPrimary


J40/290 High density polyethylene/ polypropylene studded cavity drain membrane

Specification data - Plastics sheets

Product Reference

Hydroduct® CF 08

Designed to form drained cavities vertically in lower risk applications.

Hydroduct® CF 20

Designed to form drained cavities horizontally and vertically.

Standard product features

Membrane thickness:

  • Hydroduct® CF 08: 0.6 mm.
  • Hydroduct® CF 20: 1.0 mm.

Stud height:

  • Hydroduct® CF 08: 8 mm.
  • Hydroduct® CF 20: 20 mm.

Vertical drainage capacity:

  • Hydroduct® CF 08: 2.25 L/s/m.
  • Hydroduct® CF 20: 10 L/s/m.

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Platform Compatible Version Certified to

Revit 2016


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