How To Adhere Velcro Strips

What glue is best to bond velcro strips for fly screens to the top of a caravan?

The honest answer from Selleys is that gluing is not the right solution here. Selleys strongly recommends re-stitching the new strip rather than bonding it, to give a long-lasting result.

That is not a dodge. Velcro-style hook-and-loop tape is often stitched in the first place precisely because it can be very difficult to bond to, and some glues will not form sufficient bond strength to hold it in place for an extended period. Your original strip was stitched into the vinyl for that reason. If it has worn out after years of service, the stitching did its job — the tape wore out, not the fixing.

Why this particular job is harder than it looks

Three things are working against an adhesive on a caravan fly screen mount, and they compound.

The tape itself is a poor bonding substrate. Hook-and-loop tape is generally a woven or moulded polyolefin. Polyethylene and polypropylene are the two plastics that almost every product in the Selleys adhesive range explicitly excludes — the epoxies, the contact adhesives, Hold Up and the shoe repair adhesive all carry the same statement that they will not bond polyethylene or polypropylene. If the backing of your tape is one of those, a general-purpose adhesive has no chance of a durable bond regardless of how strong it is on other materials.

Caravan vinyl is plasticised. Flexible vinyl contains plasticisers that migrate over time, and plasticiser migration is a known enemy of adhesion. Selleys flags this directly in its sealant data: the Roof & Gutter Silicone data sheet, for example, warns to avoid contact with materials containing high levels of plasticisers such as rubber and bituminous substrates. A bond made today onto plasticised vinyl is not the same bond in two summers' time.

The loading is peel, not shear. Every time the fly screen is pulled open, the load on the tape is a peel force at one edge, which is the weakest way to load any adhesive bond. Stitching resists this because the thread passes through both materials; an adhesive film can only resist it in tension across a very thin line. This is the underlying reason the manufacturer stitched it, and the reason Selleys' advice is to stitch it again.

What to do instead

1. Remove the old worn tape and the remains of the original stitching.
2. Take the panel to a canvas, camping-trailer or upholstery repairer, or sew it yourself with a heavy-duty machine and UV-stable outdoor thread if you have one.
3. Stitch the new strip through both the tape and the vinyl, along both long edges of the strip, so peel loads are carried by thread rather than by any surface bond.
4. If the needle holes leave you concerned about water ingress on a roof-line seam, seal the stitch line afterwards with a product rated for the substrate and for outdoor UV exposure — and pre-test it on an offcut of the vinyl first, because of the plasticiser issue above.

If you are set on an adhesive anyway

Selleys does not nominate a product for this application, and there is no published figure for hook-and-loop tape on caravan vinyl in any Selleys technical data sheet. If you decide to try one regardless, treat it as an experiment rather than a repair, and do three things.

Identify the tape backing. If it is polyethylene, polypropylene or PTFE, stop — nothing in the general range will hold it. Selleys directs difficult plastics to Selleys All Plastics, a two-step primer and adhesive system made for plastics that ordinary glues will not bond.

Test on an offcut, not on the caravan. Bond a short length of the new tape to a scrap of the same vinyl, let it reach full cure, then try to peel it. A bond that fails on the bench will certainly fail on the roof.

Assume it is temporary. A glued strip on the top of a caravan is exposed to UV, heat cycling, rain and constant peel loading. Even where an initial bond forms, none of the Selleys data sheets support a claim that it will survive that combination for an extended period — which is precisely the reason for the re-stitching recommendation.

Safety: if you try the adhesive anyway, you are doing it on a roof

The recommendation above is to stitch, and the safety case points the same way as the durability case, which is unusual enough to be worth saying. Stitching carries no chemical hazard at all. Both adhesives that come up as candidates carry the signal word Danger.

All Plastics and Kwik Grip Horizontal both carry H225, highly flammable liquid and vapour; H319, causes serious eye irritation; and H336, may cause drowsiness or dizziness. Kwik Grip Horizontal adds H315, causes skin irritation.

The location is what turns H336 from a nuisance into the main risk. This job is done standing on a caravan roof, or on a ladder leaning against one. Solvent narcosis — drowsiness, dizziness, a moment of not quite having your balance — is a fall hazard before it is anything else, and a caravan roof offers nothing to grab. Wind helps with the vapour and does nothing for the footing. If you are going to try a bonded strip at all, bond it to the panel on the ground and refit the panel, rather than gluing in place at height.

Heat and a Category 2 flammable liquid are a poor combination on a roof. A caravan roof in the sun runs hot, and Kwik Grip Horizontal's whole method is to leave the solvent film open for 20 to 40 minutes while it flashes off. That is a long, hot, uncontrolled release right next to a vehicle that carries gas bottles and a gas fridge vent. Do the work in the shade or early, keep the gas off, and keep the bottles well away from the open adhesive.

The test the page already asks for is also the safe way to work. Bonding a short length to a vinyl offcut belongs outdoors on a bench, where ventilation is free and you are not overhead. H319 matters more than it looks on an overhead or near-vertical surface, because gravity puts anything that runs or flicks straight onto your face — wear eye protection for any application above shoulder height.

There is no lower-hazard adhesive to recommend for this substrate, because there is no adhesive Selleys nominates for it at all. The alternative here is not a different product; it is the needle and thread.

Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand.

Common questions about gluing velcro strips

Why does Selleys recommend stitching rather than glue?

Because Velcro can be very difficult to bond to, and some glues will not form sufficient bond strength to hold it in place for an extended period. Stitching gives a long-lasting solution.

Is there a Selleys glue that bonds hook-and-loop tape?

Selleys does not nominate one for this application. The general-purpose adhesives in the range state they will not bond polyethylene, polypropylene or PTFE, which is what many tapes are made from.

What about a contact adhesive?

Contact adhesives such as Kwik Grip Horizontal are made for broad, close-fitting rigid surfaces and are not suitable for rough or ill-fitting surfaces. They also carry the same polyethylene and polypropylene exclusion.

Will a construction adhesive work?

Hold Up is for mounting and bonding tasks on materials such as timber, metals, glass, masonry and tiles, and it states it is not for some plastics — polyethylene, polypropylene and PTFE — or some rubbers. It is not intended for fabric tape on flexible vinyl.

Can I glue to the vinyl at all?

Vinyl is a plasticised material, and Selleys data sheets warn about contact with materials containing high levels of plasticisers. Any bond to flexible vinyl should be pre-tested on an offcut and treated as needing periodic checking.

My original stitching failed rather than the tape. Now what?

Re-stitch with UV-stable outdoor thread. Thread on a caravan roof degrades in sunlight long before the vinyl does, and it is the component that is cheap to replace.

What if the tape is sewn to a section I cannot get under a machine?

A canvas or camping-trailer repairer will have a walking-foot machine and long-arm access for exactly this kind of panel. It is a small job for them.

What about a difficult plastic I cannot identify?

If in doubt, test in a small hidden area first. Selleys repeats that instruction across the range wherever plastics are involved, because the same product can behave very differently on two plastics that look identical.