Resin Bonded Cork Filler

Bonded granular cork expansion joint fillers


Fosroc Cork Fillers are a range of bonded cork expansion joint fillers particularly recommended for use in immersed conditions. There are two in the range:

  1. Self-expanding Cork Filler (Hydrocor)
  2. Resin-bonded Cork Filler

Both products can be used as expansion joint filler for joints in:

  • Water retaining structures
  • Water excluding structures
  • Roads, bridges and traffic surfaces
  • External walling and cladding
  • Services and internal finishes

Standards Compliance

Self-Expanding Cork Filler(Hydrocor)

Complies with ASTM D1752-67 (R73) Type III and American National Standard A37. 114-1969 (R75) Type III.

Resin-bonded Cork Filler

Complies with UK Dept. Of Environment (MoPBW) Specification No. 201, Clause 606, and ASTM D1752-67 (R73) Type II and American National Standard A37. 114-1969 (R75) Type II


There are two types of Fosroc Expandite Cork Filler:

Self-expanding Cork Filler (Hydrocor):

Self-Expanding Cork Filler (Hydrocor) consists of cork granules bound together with an insoluble, synthetic resin. When subjected to wet or moist conditions, it is capable of swelling to occupy a larger volume than that of the material as supplied.

Self-expanding Cork Filler (Hydrocor) is suitable for use in all types of concrete construction. It is particularly recommended for use in water retaining structures where it is essential that joints remain tightly packed even if they increase in width.

Resin Bonded Cork Filler:

Resin-bonded Cork Filler consists of granulated cork bound together with a synthetic resin. It contains no bitumen or tar and cannot impair the adhesion of any joint sealing compound by contaminating the joint faces.


Water retaining structures

Self-expanding Cork Filler (Hydrocor) is particularly recommended for filling expansion joints in irrigation canals, culverts, dams, reservoirs, sea walls, sewage works, swimming pools, water treatment and storage structures.

Example of sealed expansion joints in floors of reservoirs, irrigation canals, swimming pools, basements and subways is shown below.

Water excluding substructures

Cork Fillers are recommended for filling expansion joints in basements, site slabs and subways.

Roads, bridges, traffic surfaces

Cork Fillers are suitable for filling expansion joints in pedestrian and other areas not subject to heavy traffic loads.

External walling and cladding

Cork Fillers are recommended for filling structural expansion and structural separation joints in brick, block and insitu concrete construction where load transfer across the joint can be tolerated.

Example of sealed expansion joint in brickwork in shown below.

Service and internal finishes

Cork Fillers are recommended for filling expansion joints across ducts in concrete floors, including screeded floors with underfloor heating. Resin-bonded Cork Filler may be used as beam bearing pad.

Example of sealed expansion joint in floor surface are shown below.

Site instructions

Fosroc Cork Fillers are supplied in sheet form and may be sawn or drilled as required. They are used to form and fill expansion joints. In concrete: Fosroc Cork Filler should be fixed, using dabs of Supastik Contact Adhesive, spreading grade, to the face of the first placed concrete after which the second placed concrete is cast.

A sealing slot can be formed by placing on top of the Cork Filler a strip of soft wood or other former which can be removed later, or a sealing slot can be formed by filling the entire depth of the joint with Cork Filler and subsequently cutting out to the designated depth with an Fosroc Power Brush Machine equipped with a cruciform cutter. 

In brick and block work: Fosroc Cork Filler should be installed whilst laying brick or block work and should be so placed that a sealant slot is formed. Ensure that the sealant slot formed is free from mortar droppings.



Self-expanding CorkFiller (Hydrocor) is supplied in sheets of 610 x 915 mm in three standard thicknesses: 12.5 mm, 20 mm and 25 mm.

Resin Bonded Cork Filler is supplied in sheets of 610 x 915 mm in five standard thicknesses: 12.5 mm, 20 mm and 25 mm.


Caution: Self-expanding Cork Filler (Hydrocor) must be stored in sealed plastic bags.


Health and safety

Cork Fillers: There are no health hazards associated with Fosroc Cork Fillers in normal use.


Supastik Contact Adhesive: Highly flammable. Flash point (minus 40ºF). Store away from heat. Do not use near a naked flame. Avoid unnecessary inhalation of vapour.

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