How To Attach Limestone to Fibreglass Pool
What attaches a reconstituted limestone bullnose to a fibreglass pool?
Check the Liquid Nails Landscape specification
Selleys' product page and its dated technical sheet disagree on Landscape's chemistry, colour, paintability and pack size. Landscape figures below from the November 2020 technical sheet describe that document, not a confirmed specification for every current cartridge. Confirm the matching instructions before painting, choosing a colour, or relying on cure and loading times. See the source comparison and dated documents.
The Selleys recommendation for this is Liquid Nails Landscape, used to bond the poolside bullnose and also to seal underneath it.
Before you commit to it, read the limitations section below carefully, because this job sits close to the edge of what the product's technical data sheet actually covers. Two points in particular need checking against your own installation.
- The materials list on the Liquid Nails Landscape data sheet is stone, concrete, capstones, terracotta and timber. Fibreglass is not on it.
- The data sheet states the product is not for permanent water immersion. A coping stone above the waterline is not immersed; anything at or below the water line is.
Reconstituted limestone against a concrete beam is squarely within what the product is made for. The fibreglass shell edge is the part to verify, and the safest way to do that is a bond test on an offcut plus a call to your pool manufacturer, who will have a view about what may and may not be bonded to their shell lip.
Why coping is different from the rest of a landscaping job
The bullnose around a pool has a harder life than almost any other bonded stone in a garden.
The water line is a wetting and drying cycle, not a soak. The stone is repeatedly splashed, then dried by sun and wind. That cycling drives salts into and out of porous stone, and it is much more aggressive on a bond line than constant immersion would be.
Reconstituted limestone is porous and relatively soft. Liquid Nails Landscape states it is not for soft or crumbly materials. Reconstituted limestone is a manufactured stone product with a range of densities; a dense, well-cured unit is fine, a soft or friable one is not. Break a corner off an offcut and see how it behaves before you glue a whole run down.
Fibreglass and stone move at very different rates. A fibreglass shell expands and contracts far more than a concrete beam does, and it flexes as the pool fills and empties. This is the argument for a flexible adhesive rather than a rigid one, and Landscape does deliver a flexible, shock proof bond with elongation greater than 300% — but it is also the reason to bond primarily to the concrete beam and let the fibreglass interface be a seal rather than a structural bond.
The figures
| Property | Liquid Nails Landscape |
|---|---|
| Technology | Neutral cure silicone |
| Colour | Grey |
| Packaging | 300 g cartridge |
| Skin time | 10–15 minutes |
| Tack free time | 35 ± 5 minutes |
| Cure rate | 2 mm / 24 hours |
| Shore A hardness | ~30 |
| Elongation at break | >300% |
| Slump | < 0.1 inch |
Indicative data only, not intended for the preparation of specifications.
The cure rate is the figure that matters most here. At 2 mm per 24 hours, a bed under a bullnose unit is not cured for several days, and until it is cured it has no water resistance to speak of. Do not fill the pool, and do not let the joint get wet, until the adhesive has cured through. The data sheet's own instruction is to leave it undisturbed until the adhesive cures sufficiently, with no traffic or loading for at least 24 hours — on a thick bed under coping, allow considerably longer than that.
How to lay the bullnose
- Speak to the pool manufacturer first about what may be bonded to the shell lip, and check whether their warranty or installation guidance specifies a coping method.
- Test the bond on offcuts: a scrap of the limestone and a piece of the same fibreglass. Let it cure fully, then try to break it.
- Ensure all surfaces are sound, dry and free from oil, grease and loose powdery material. If necessary, clean with mineral turpentine and allow it to dry. Fibreglass gel coat frequently carries mould release wax — this must come off.
- Dry-lay the run and mark it. Set your falls away from the pool.
- Cut the cartridge tip, fit the nozzle and cut a suitable opening — approximately 5 mm. Use a caulking gun.
- Apply dobs or beads of adhesive of appropriate thickness to ensure sufficient contact and spread between both surfaces, at least 12 mm in from the edges to minimise squeeze-out. Concentrate the bonded area on the concrete beam.
- Immediately bring the surfaces together before the product skins — within 5 minutes — and apply sufficient pressure to spread the adhesive.
- Use the same product to seal underneath the bullnose where it meets the shell, forming a continuous seal so water is shed outwards rather than tracking behind the stone.
- Do not wipe squeeze-out. Let it cure and trim it with a sharp blade, avoiding cutting into the bond. On a visible coping edge, mask before you start.
- Keep the joint dry and unloaded until it has cured through.
Limitations — read these before you buy
- Not for permanent water immersion. This is the decisive one for a pool. Coping above the water line is within scope; anything at or below the water line is not.
- Fibreglass is not among the materials listed on the technical data sheet, which names stone, concrete, capstones, terracotta and timber. Test the bond on an offcut before relying on it.
- The data sheet publishes no chemical resistance data for chlorinated or salt water. If long-term chemical exposure is critical to your installation, ask Selleys directly rather than inferring it.
- Not for soft or crumbly materials. Check the density of your reconstituted limestone.
- Do not use as the sole bonding agent for structural bonding. Coping that people stand and sit on should be properly bedded and supported, not held on by adhesive alone.
- If repositioning materials, fresh adhesive must be applied to achieve bonding.
Clean up
Uncured product removes with mineral turpentine. Cured product can be removed with Selleys Sealant Remover or by mechanical action. Spilt or smeared adhesive is best left to cure and then removed by abrasion — awkward on porous limestone, so mask the visible faces first.
Safety: working with solvents at a pool edge
One of the classifications to check on this page belongs to Selleys Sealant Remover, named in the clean-up section above. It is classified Danger under Safe Work Australia GHS 7, Poison Schedule S5, and carries H304 (may be fatal if swallowed and enters airways), H226 (flammable liquid and vapour), H336 (may cause drowsiness or dizziness) and H315 (causes skin irritation). Over 60% of the tub is petroleum naphtha. Liquid Nails Landscape's Australian SDS version 7.0, 16 November 2023, lists Danger: H227, H317 and H318 — combustibility, allergic skin reaction and serious eye damage. Follow the matching pack and SDS for protection, handling and first aid.
What that means around a pool
H304 is the classification to take most seriously, and the pool setting is why. Aspiration hazard Category 1 means that if the material is swallowed and any reaches the airways it can cause a chemical pneumonitis that is potentially fatal. Light hydrocarbons flow rather than being coughed back, so the first aid is to never induce vomiting. A 375 g screw-top tub of beige paste sitting open on coping, at a pool, where children are, is the exact circumstance the Schedule 5 listing exists for. Lid back on between applications, and store it away from the pool area entirely.
The remover attacks the same materials you are working next to. Its own limitations exclude rubber, EPDM and polycarbonate — the family of materials that turns up around a pool as skimmer box seals, flexible jointing and polycarbonate covers or fencing panels. A hydrocarbon solvent does not distinguish between the cured sealant you want gone and an EPDM seal it runs onto. Mask, and scrape the bulk away mechanically first.
H226 and H336 point at where you position yourself. Coping work is done kneeling, face down, close to the joint — the worst posture for breathing your own solvent vapour. Outdoors that clears quickly; in a covered pool enclosure it does not. Gas pool heaters and pumps sit at ground level nearby and are a real ignition source for a Class 3 flammable liquid, not a theoretical one. Shut them down before you open the tub, and keep the mineral turps used for the gel-coat prep in the same category.
Nitrile gloves and safety glasses for both products. You are scraping material back towards yourself at face height.
The lower-hazard route for removing cured squeeze-out is the one already given above: mask before you start, let it cure, and trim it with a blade. Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand.
Common questions about pool coping
Will Liquid Nails Landscape stick to fibreglass?
Selleys recommends it for this application, but fibreglass is not among the materials listed on the product's technical data sheet. Test the bond on an offcut of your shell material before committing.
Can it go under water?
No. The data sheet states it is not for permanent water immersion. Keep the bond line above the water line.
Is it resistant to chlorine and salt?
No chemical resistance data for chlorinated or salt water is published on the data sheet. Ask Selleys directly if this is critical to your installation.
How long before I can fill the pool?
Cure runs at 2 mm per 24 hours and the directions call for at least 24 hours undisturbed. A thick bed under coping takes several days — allow generously and keep the joint dry until then.
Can I use the same product to seal under the bullnose?
Yes. Selleys recommends using Liquid Nails Landscape to seal under the bullnose as well as to bond it.
Does the fibreglass need preparation?
Ensure it is sound, dry and free from oil, grease and loose powdery material, cleaning with mineral turpentine if necessary. Gel coat often carries mould release wax that must be removed.
My limestone is quite soft. Is that a problem?
Possibly. The product is not for soft or crumbly materials. Test a piece before you lay the run.
Should I bed the coping in mortar instead?
For coping that will be walked and sat on, a properly bedded installation is the conventional approach, with adhesive supplementing rather than replacing it. The data sheet is explicit that this product is not to be used as the sole bonding agent for structural bonding.
Who should I ask about the pool shell?
The pool manufacturer. They will tell you what may be bonded to the shell lip and whether their warranty depends on the coping method.
What colour is it?
Grey, which suits most limestone and concrete. There is no other colour in Landscape.
What product does Selleys recommend for attaching a reconstituted limestone poolside bullnose onto a fibreglass pool?
Selleys recommends Marine Flex for attaching a reconstituted limestone poolside bullnose onto a fibreglass pool, surrounded by a concrete beam, especially since the adhesive must withstand chlorinated saltwater.
Why is Marine Flex suitable for this pool application?
Marine Flex is specifically designed for pool environments and works on fibreglass and for waterproofing seals where water contact occurs. It offers waterproof performance suitable for above and below waterline applications, superior durability compared to traditional polyurethane products, no primer requirement on fibreglass surfaces, shock-absorbing and vibration-dampening properties (useful for material movement), and non-sagging characteristics for vertical applications.
Does Marine Flex require a primer when used on fibreglass surfaces?
No, Marine Flex does not require a primer when applied to fibreglass surfaces.
How should the fibreglass pool surface be prepared before applying Marine Flex?
The fibreglass surface should be clean and free from oil, grease, and loose particles, and should be lightly sanded prior to application to enhance adhesive strength. Metal and plastic surfaces should be wiped with a solvent such as mineral turpentine to remove all traces of oil and mould release residue.
How is Marine Flex applied to attach limestone to the pool?
Marine Flex is applied using a caulking gun, pushing the sealant into the joint or gap between the limestone and fibreglass. The application can be smoothed using a spatula within 15 minutes of applying the product.
Is Marine Flex confirmed to work well on limestone specifically?
Not explicitly. The technical data does not confirm limestone as a tested substrate for Marine Flex. Since limestone is porous and Marine Flex is primarily tested on ceramic tiles, fibreglass, glass, and other standard pool materials, it is strongly recommended to conduct a pre-test on a small area before full installation to ensure acceptable adhesion and performance.