8. Bonding GRP to other materials

Lead

Lead (and concrete) can be primed with G4 Dampseal (which will prime many surfaces and facilitate adhesion when applying fibreglass).
G4 should be thinly applied with a brush or roller and allowed to tack before applying the laminate.
The G4 film should be left no more than 2hrs before the application of the laminate as the bond strength diminishes as the G4 film moves towards a full cure.
Alternative preferred method. Abrade the lead with 40-60 grit aluminium oxide. Apply a thin film of Matrix Trim Adhesive (around 1mm) and gently “pad in” a strip of pre-cut glass mat. Do not force the adhesive fully through the mat – rather engage the mat in the adhesive and let it cure (around an hour to dust free film). You now have a piece of dry mat flexibly bonded to the lead but available to receive more mat and resin on the top (dry) surface thus bonding the new laminate to the lead.
A joint formed using Matrix Trim Adhesive will remain flexible and will better accommodate the disparate thermal expansion and contraction that occurs between lead and GRP.
This method can be applied to pipes and balcony railings and other areas where it is difficult to achieve a bond between different materials. It can also be used to “anchor” a new GRP liner into an old lead or zinc gutter. Ring us for more information on this application.
This method can also be used to configure a GRP laminate on a Mansard Roof. Contact Matrix for more advice.

Concrete

You can bond to concrete using G4 Dampseal as a primer (see above) available from your distributor.
The concrete should be clean and dry and fully cured (2-3 weeks minimum) and there should be no small pieces of loose aggregate which may compromise the laminate and cause poor adhesion to the surface.
For smaller areas or where you need increased flexibility use Matrix Trim Adhesive to obtain a good intermediate bond. (as above)

Asbestos

GRP bonds very well to asbestos but the asbestos must be clean and dry. We do not recommend power washing or abrading asbestos (it produces dangerous slurry or dust) and we strongly recommend engaging an asbestos professional for advice.

Bituminous surfaces (bitumen, felt and asphalt)

Bitumen inhibits the cure of GRP but on small areas it can be neutralised by a coat of G4. Applied with a brush or short pile roller G4 will initially soften the bitumen and will then harden off sufficiently to accept a GRP laminate – but it is much better to replace the boards or even overboard with 18mm OSB3 Sterling. We do not recommend laminating onto asphalt which must be over-boarded before applying a GRP laminate.

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