How To Glue Black Rubber to Solar Panel

What is the best product for fixing black rubber solar pool heating strips to a concrete tile roof?

Solar pool heating matting is normally bonded in place with a silicone sealant rather than a glue, and the Selleys recommendation for this job is Selleys Roof & Gutter Silicone. The important detail is how you apply it: run the sealant in vertical beads, evenly spaced down the slope, rather than as one continuous bead. A continuous bead effectively seals the strip to the tile and dams water running down the roof, which is the last thing you want on a tiled roof that relies on water shedding freely.

Before you start, there is one limitation you need to know about, because it is not obvious and it decides whether this job lasts. Read the section on rubber below before you commit to gluing the whole array down.

Why Roof & Gutter Silicone suits the roof side of this job

Selleys Roof & Gutter Silicone Sealant is a neutral-cure, 100% silicone sealant made for roofing, gutters and flashings. Neutral cure matters on a roof because it does not release acetic acid as it sets, and it is the type Selleys specifies for coated metal and Colorbond sheet. It carries a 25-year guarantee against crumbling, cracking and peeling when used as directed for private use and within 12 months of purchase.

Its published figures explain how it behaves once it is on the roof:

• Skin time 5–10 minutes, tack-free at 30 minutes, tooling time 5 minutes — a short window to position the strip, and none at all to reposition it later.
• Cure rate 2 mm per 24 hours. A 6 mm bead is roughly three days through its section, not three hours.
• Joint movement ±25%, elongation at break 330% (ASTM D412), Shore A hardness 32 — it stays flexible rather than going brittle in the sun.
• Service temperature −60 °C to +150 °C, which covers a dark roof in an Australian summer.
• Application temperature +5 °C to +30 °C, and the TDS says not to apply it if the ambient or substrate surface temperature is below +5 °C or above +40 °C. On a north-facing tile roof in January that rules out the middle of the day.

The concrete tile itself is a substrate the TDS lists as suitable — concrete and masonry are both named porous substrates, alongside brick, timber, plywood and fibre-reinforced cement.

The rubber side: pre-test before you commit

This is the part worth slowing down for. The Roof & Gutter Silicone technical data sheet carries an explicit limitation: avoid contact with materials containing high levels of plasticisers, such as rubber and bituminous substrates. Selleys' technical guidance is that components in some rubber products can migrate into the sealant, causing staining or reduced performance.

Solar pool heating matting is a rubber-family product, so the sensible course is to test a short length first rather than glue the whole array and hope. Selleys' own recommendation on this sealant is that users apply a sample to the intended area to confirm appearance, finish and performance before doing the full job. Bond two or three beads onto a spare tile, leave them a few days to cure properly, and try to peel the strip off. If it holds and the sealant has not softened or discoloured, carry on. If it peels cleanly, the plasticiser issue is real on your particular matting and you need a mechanical fixing system from the heating supplier instead.

The TDS also rules out polyethylene, polypropylene and PTFE (Teflon) entirely, so if the matting turns out to be a polyolefin rather than rubber, silicone is not the answer at all.

How to apply it

1. Pick a mild, dry day. Work outside the +5 °C to +40 °C surface temperature limits and the sealant will not perform as published.
2. Make sure the tiles are clean, dry, sound and free of dust, oil, moss and other contaminants. Remove any old adhesive or sealant from previous fixings.
3. Wipe the non-porous side — the underside of the strip — with a clean cloth dampened with isopropyl alcohol or white spirit, wiping in one direction only, then immediately wipe with a clean dry cloth.
4. Cut the cartridge tip, screw on the nozzle and trim it to the bead size you want. A high-thrust-ratio caulking gun makes a 300 g cartridge of silicone far easier to control.
5. Apply the sealant as separate vertical beads, evenly spaced, running with the fall of the roof. Do not ring the strip or run a bead across the slope.
6. Press the strip down onto the beads within the tooling window and hold or weight it until it takes up. There is no repositioning once it skins.
7. Clean excess off tools with turps before it cures. Once cured it has to come off mechanically or with Selleys Sealant Remover.

Limitations worth knowing before you start

• Not paintable. If the roof is to be painted, paint it first and allow at least 7 days before sealing.
• Not for continuous submersion or below-waterline use. It is fine for rain and weather, but it is not a pool-line sealant.
• Not for structural glazing.
• It needs atmospheric moisture to cure. On non-porous substrates or in very dry weather, curing slows down. Do not expect the published 2 mm/24 hours in low humidity.
• Plasticiser migration from rubber or bituminous materials, as covered above.

Safety: this job is on a roof, which changes the calculation

Roof & Gutter Silicone is classified Warning — H319 (causes serious eye irritation) and H317 (may cause an allergic skin reaction).

Selleys Sealant Remover, named in the clean-up step above, is in a different class. It is Danger, 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). It is more than 60% petroleum naphtha.

What follows on a tiled roof

H336 is a fall hazard here, not a comfort problem. Drowsiness and dizziness from solvent vapour is a nuisance in a garage. On a pitched tile roof it is the thing that puts you off the edge. If you are stripping old sealant from a previous fixing with Sealant Remover, work upwind of the material, take breaks off the roof, and stop entirely if you feel light-headed — that sensation is the exposure standard being exceeded, not something to push through.

H226 and a hot roof do not go together. A Class 3 flammable liquid should not be sitting open in full sun on dark tiles. The same temperature limit that governs the silicone — do not apply above +40 °C surface temperature — is a good rule for where you leave the solvent tub. Work early, and keep it in the shade.

Keep the remover off the matting. Sealant Remover explicitly excludes rubber and EPDM. The thing you are bonding is rubber pool-heating strip, so a solvent paste that softens cured sealant will attack the matting just as readily. Scrape mechanically around the strips rather than spreading remover near them.

H317 on the silicone is about the number of beads, not the strength of one. Sensitisation is the immune system learning to react — generally permanent once acquired, then triggered by far smaller exposures. A solar array is a long run of vertical beads with the strip pressed down onto each one, which is hours of hand contact. Gloves for the whole job, not just the first cartridge.

H319 pairs with your working position. You are guning beads at tile level with your face close to the work and a caulking gun that can spit when pressure releases. Safety glasses.

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

Common questions

Why not just run one continuous bead around the strip?

Because it seals the strip to the tile and prevents water flowing down the roof from getting away, allowing it to pond. Evenly spaced vertical beads hold the strip and still let water run through.

How long before the strips are properly held down?

The silicone is tack-free at about 30 minutes, but it cures at 2 mm per 24 hours, so a bead of any real thickness takes several days to reach full section. Support the strips over that period and do not stress the bond.

Will it stick to Colorbond or coated metal panels?

Yes. Roof & Gutter Silicone is specifically listed as suitable for common roofing substrates such as Colorbond sheet and coated metal panels, as well as aluminium, steel, stainless steel, galvanised steel and PVC.

Can I paint over the sealant afterwards to hide it?

No. The TDS states plainly that Roof & Gutter Silicone is not paintable. It comes in a wide range of Colorbond-matched colours instead, so choose a colour close to the tile.

What if the matting is a plastic rather than rubber?

Check with the heating supplier. Roof & Gutter Silicone is not for use on polyethylene, polypropylene or PTFE, and no amount of surface preparation changes that.

What temperature is too hot to apply it?

Do not apply it when the ambient or substrate surface temperature is below +5 °C or above +40 °C. A dark tile roof exceeds 40 °C easily on a hot afternoon, so work early or on a mild day.

How do I clean up the mess?

Turps removes wet sealant from tools. Cured sealant has to be removed mechanically or with Selleys Sealant Remover.

Is this sealant suitable for other roof jobs?

Yes — it is made for sealing joints around roofs, gutters, flashings, skylights and tile roofing. See also sealing leaking aluminium roof panelling.