SKU: 5600

G4 Damp Sealer (5KG)

Name: G4 Damp Sealer (5KG)
Brand: Pond
SKU: 5600
Price: 70.404 GBP
Availability: InStock

£58.67

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G4 Damp Seal for concrete roofs and fibreglass-lined ponds

G4 Damp Seal is the correct G4 product when polyester resin and fibreglass will be applied over a suitable concrete or rendered surface.

It seals porous concrete before GRP sheathing and helps prevent alkali within the concrete from reacting with the polyester resin. It is suitable for concrete flat roofs and concrete or rendered ponds that will subsequently receive a fibreglass lining.

Concrete roof primer Fibreglass pond primer Apply before GRP

The G4 Damp Seal technical data states:
“Sealing concrete prior to fibre glass sheathing where alkali in concrete can react with resins.”

Which G4 product do I need?

Applying fibreglass or GRP afterwards?

Use G4 Damp Seal. This includes suitable concrete roofs and concrete or rendered ponds that will receive a polyester resin and fibreglass laminate.

Sealing a masonry pond without fibreglass?

Use G4 Pond Sealer as the finished standalone pond-sealing coating.

Shop G4 Pond Sealer

Do not confuse this product with G4 Pond Sealer.
G4 Pond Sealer is a standalone pond coating. Its current technical data states that it is not compatible with fibreglass, so it must not be used as the primer beneath a subsequent GRP laminate.

Where would I use G4 Damp Seal?

Sealing suitable concrete flat roofs before polyester GRP sheathing
Preparing concrete or rendered ponds before installing a fibreglass lining
Sealing porous concrete where alkali could react with polyester resin
Damp-proof sealing of suitable floors and porous surfaces
Preparing plug surfaces before mould production
Improving the bond of GRP to suitable metal surfaces

Product description

G4 Damp Seal is a moisture-curing, single-part polyurethane varnish for sealing damp and porous surfaces. It forms a hard-wearing, non-porous coating and is particularly useful where concrete is being prepared for polyester GRP sheathing.

It can also be used on plug surfaces before applying a release agent and taking a mould, as release agents and polyester resins do not attack the G4 coating.

G4 Damp Seal may also be used to improve the bond of GRP to suitable metal surfaces. It withstands temperatures up to 200°C and provides good chemical resistance.

Coverage and tin-size guide

The manufacturer gives a nominal consumption rate of approximately 500g per m². For most sealing purposes, three coats are recommended to build a continuous surface film.

Tin size	Approximate three-coat coverage
1kg	Approximately 2m²
2.5kg	Approximately 5m²
5kg	Approximately 10m²
25kg	Approximately 50m²

These figures relate to the manufacturer's nominal rate for the complete sealing application. Consumption will vary according to the porosity, texture and condition of the substrate. Rough or highly absorbent concrete may require more material.

The modern technical data does not provide a separate coverage rate specifically for a GRP bonding application over concrete.

Key technical information

Application	Brush or roller
Coats	Three coats recommended for most sealing purposes
Drying time	Approximately 60–90 minutes
Recoat time	Recoat when finger tacky and do not allow more than four hours between coats
Application temperature	Can be applied at temperatures down to 0°C
Clean-up	Clean equipment using Rustins Cellulose Thinners. Turpentine and White Spirit are unsuitable.

Choose your application

Open the guide that matches the surface you are fibreglassing.

Using G4 Damp Seal on a concrete roof

G4 Damp Seal can be used where a polyester GRP roofing system will be applied directly over a suitable concrete substrate.

Inspect the concrete. It must be structurally sound, bare and sufficiently porous to accept the coating.
Clean and dry the surface. Remove paint, existing coatings, sealers, oil, grease, dust and other contamination that could interfere with adhesion.
Repair defects before coating. Repair loose, cracked, damaged or worn areas. G4 should not be relied upon to fill cracks, holes or defective concrete.
Apply by brush or roller. Work the product evenly into the porous surface and avoid allowing it to puddle in depressions.
Follow the selected GRP system instructions. The modern G4 Damp Seal TDS confirms its use before fibreglass sheathing, but it does not provide a separate concrete-roof coat quantity or GRP laminating window.
Observe any required bonding window. Apply the polyester laminate in accordance with the instructions supplied with the selected GRP roofing system.

Important coverage note:
The stated 500g per m² and three-coat recommendation relate to general sealing applications. Do not assume that the same quantity is required for every direct-to-concrete GRP installation.

Direct-to-concrete GRP or overboard the roof?

Direct application: Where the concrete is bare, dry, sound, porous and suitable for direct lamination, G4 Damp Seal can be used before the selected polyester resin and fibreglass system is applied.

Overboarding alternative: A new insulated warm-roof build-up can instead be constructed over the existing concrete or asphalt roof.

The build-up can include suitable insulation, supporting battens and an 18mm OSB3 tongue-and-groove deck. The GRP laminate and topcoat are then installed over the OSB3 deck.

Because the fibreglass is applied to the new timber deck rather than directly to the concrete, G4 Damp Seal is not normally required as the GRP primer in this type of build-up.

The roof structure, insulation, battens, fixings and deck must be suitable for the installation and comply with the selected roofing-system requirements.

Using G4 Damp Seal before fibreglassing a pond

Fibreglass lining the pond?
Use G4 Damp Seal to prepare the suitable concrete or rendered surface. Do not substitute G4 Pond Sealer beneath the laminate.

Check the pond structure. The concrete base, block walls and render must be stable, sound and suitable to receive a bonded fibreglass lining.
Prepare an even rendered surface. Remove exposed aggregate, rough projections, sharp points, lumps and loose material that could interfere with the laminate.
Radius the corners. Internal and external corners should have a gradual radius rather than a sharp 90-degree edge, helping the fibreglass reinforcement conform to the shape.
Allow the render to dry. Keep the pond protected from rain and standing water while the render dries.
Clean the surface thoroughly. The render must be clean, dry, sound and free from dust, contamination, paint, existing sealers and loose material.
Prepare materials before starting. Cut and organise the fibreglass reinforcement before mixing catalysed resin, as the available working time will be limited.
Apply G4 Damp Seal. Apply by brush or roller, working the product into the porous concrete or render and avoiding puddles or excessively thick areas.
Apply the laminate within the pond-lining system's bonding window. The supplied pond-lining guidance advises applying the polyester resin and matting once the G4 has reached a tacky state and not allowing more than four hours to elapse.
If the G4 has fully hardened, stop and prepare it again. The pond-lining guidance advises abrading the hardened surface and removing all dust and debris before continuing.

General fibreglass pond-lining notes

The supplied pond guidance recommends two layers of 450g chopped strand mat for improved reliability over rendered surfaces.
Start with the pond walls and allow approximately 75mm overlaps onto adjoining surfaces and the pond base.
Stagger the joints in the second layer rather than positioning them directly over the first-layer joints.
Consolidate each laminate layer thoroughly to remove trapped air and ensure the resin fully wets the reinforcement.
Inspect for dry patches and raised fibres before applying surface tissue and the final pond topcoat.
Follow the resin, catalyst, laminate and topcoat instructions supplied with the complete pond-lining system.

Do not apply fibreglass over G4 Pond Sealer.
The current G4 Pond Sealer technical data states that Pond Sealer is not compatible with fibreglass. G4 Damp Seal and G4 Pond Sealer are different products for different systems.

Features

Suitable before fibreglass sheathing over concrete
Suitable for concrete roofs and fibreglass-lined ponds
Nominal sealing coverage rate of 500g per m²
Apply by brush or roller
Hard-wearing and non-porous
Moisture-curing, single-part polyurethane varnish
Can be applied at temperatures down to 0°C
Withstands temperatures up to 200°C
Good chemical resistance

G4 Damp Sealer (5KG)

£58.67

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G4 Damp Sealer (5KG)