An oil-based mastic, suitable for perimeter sealing of timber frames and sealing of preformed concrete panels, e.g. for garages.

Not recommended for high movement joints or expansion joints.

Resistant to dilute alkalis and acids. Should not cause staining on many common building materials, but may stain porous materials such as marble, slate and other natural and reconstituted stones.

Flash point: 65°C.

Good UV resistance but may undergo slight yellowing.

Can be painted, but excessive movement will cause the paint to crack. Bituminous paints should not be used.

Correctly applied, the sealant should not require maintenance, and has an anticipated life in excess of 10 years.

Health and safety:

Avoid prolonged skin contact. Use of this product should be recorded in the project Health and Safety Plan.

Application temperature:

+5°C to +50°C.

Curing time:

Skins after approximately 14 days depending on atmospheric conditions.

Joint dimensions:

- Width:

  • Minimum 6 mm; maximum 18 mm (single application).

- Depth:

  • Porous substrates: Minimum 10 mm; maximum 20 mm.
  • Non-porous substrates: Minimum 6 mm; maximum 10 mm.

Joint backing:

A combined joint filler/ bond breaker, such as closed cell foam polyethylene rod, should always be used to ensure that the sealant adheres only to the joint faces and not to the back. Bond breaker tape should be used where the joint has been packed out with fibre-board.


Friable or brittle surfaces will need priming with Arbo Primer 925.



Available in five standard colours.

NBS Specification

NBS Create logo
This product is associated with the following NBS Create clause:
45-55-75/330 Oil based mastic joint sealants

Product specification

An important note about specifying



Adshead Ratcliffe & Co Ltd


+44 (0)1773 826661

Product reference

Arbomast GP




[Filler: Closed cell foam polyethylene rod]
[Filler: Fibre-board with bond breaker tape]
[Primer: Arbo Primer 925]

Manufacturer details

Derby Road,
Derbyshire, DE56 1WJ
Tel +44 (0)1773 826661
Fax +44 (0)1773 821215
NBS Plus
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