What is Selleys Roof & Gutter Silicone, and where should you use it?

Selleys Roof & Gutter Silicone Sealant is a neutral-cure, 100% silicone sealant for roofing, gutters and flashings around the home. It provides a superior waterproof seal with excellent UV and weather resistance, resists lifting, and comes in a wide range of colours matched to common roof and gutter sheet profiles — including Colorbond® colour matches.

It carries a 25-year guarantee against cracking and peeling, and it is tested to AS/NZS 4020:2018 for contact with drinking water — the standard that matters when the gutter you are sealing feeds a rainwater tank. Read the qualification on that second point carefully, though: not all colours have been tested to AS/NZS 4020:2018, and Selleys directs users to check the current test reports, available on request. If potable water contact is the reason you are buying it, confirm the specific colour rather than assuming the range is covered.

Technical specification

Property	Typical result
Technology	Silicone
Cure mechanism	Moisture curing (neutral cure)
Specific gravity	1.04
Tooling time	5 minutes
Skin time	5 to 10 minutes
Tack-free time	30 minutes
Curing rate	2mm per 24 hours
Joint movement	±25%
Slump	0mm
Shore A hardness	32
Elongation at break (ASTM D412)	330%
Modulus at 100% elongation (ASTM D412)	0.6 MPa
Application temperature	+5°C to +30°C
Service temperature	-60°C to +150°C
Storage temperature	+5°C to +27°C
VOC	33 g/L
Shelf life	18 months (the storage section advises using unopened packaging within 12 months of manufacture)

These results are based on current product material data, quality test methods and testing conditions such as temperature, moisture and substrate. Conformities: AS/NZS 4020:2018 (testing of products for use in contact with drinking water) and ASTM D3960-05 for VOC content.

What the key numbers mean in practice

The tooling time of 5 minutes is the figure that shapes how you work on a roof. Skin time is 5 to 10 minutes, so the moment the surface begins to set you have lost the ability to tool the bead cleanly. The product page puts it well: work in sections that can be completed before the sealant skins, because tooling off and tape removal both have to happen inside that window or a rough surface results. A rough surface on a roof joint is not just cosmetic — it gives water somewhere to sit.

Tack-free at 30 minutes means the bead stops picking up dust and grit half an hour in. That is useful on an exposed roof, but it is not cure. The curing rate of 2mm per 24 hours describes how deep the cure travels: a 5mm-deep bead takes the better part of three days to cure through. The product page's practical guidance is to allow roughly 72 hours before exposing the joint to water and to trim any excess after curing, which lines up with that rate for a typical bead.

One condition applies to all of it: the sealant requires atmospheric moisture to cure. On non-porous substrates or in low-humidity conditions, curing speed slows. Most roofing substrates are non-porous metal, so allow more time rather than less.

±25% joint movement with 330% elongation at break and a modulus at 100% of 0.6 MPa describes a flexible, low-stress seal — one that stretches with a roof sheet's daily thermal movement without pulling the bond apart. A slump of 0mm means a bead on a vertical flashing or fascia will not sag before it skins.

Joint design

• Minimum joint width and depth is 5mm.
• The optimum width-to-depth ratio for joint sealing is 2:1.
• For widths up to 12mm, use a 1:1 ratio.
• For widths greater than 12mm, use 2:1.
• Choose a backer rod 25% to 50% larger than the joint width.
• Add 10% to 15% to your quantity estimate to account for wastage.

Where to use it

• Sealing joints around the roof, gutters, flashings, skylights and tile roofing
• Common roofing substrates such as Colorbond® sheet and coated metal panels
• Joints in air conditioning units, fences and façades

The published substrate list divides into porous and non-porous:

• Porous: timber and plywood, fibre reinforced cement, bricks, concrete, masonry
• Non-porous: aluminium, steel and stainless steel, mild and galvanised steel, powder-coated steel, PVC

Pre-test compatibility with substrates before use.

How to apply it

1. Prepare the surface. All surfaces must be clean, dry, sound and free of dust, oil, rust and other contaminants.
2. Clean non-porous surfaces with a clean cloth dampened with IPA or white spirit, wiping in one direction only, then immediately wipe with a clean dry cloth. Wiping back and forth redistributes the contamination rather than removing it.
3. Remove all existing adhesives or sealants before use on remedial work.
4. Cut the cartridge tip, screw on the nozzle and trim it to the bead size you want, then load the cartridge into a caulking gun. Use a good-quality gun — a high-thrust-ratio caulking gun suits high-viscosity products.
5. Apply a continuous bead into the joint, ensuring full contact with both sides.
6. Tool with a clean spatula dipped in soapy water before skin formation for a smooth finished joint.
7. Allow the sealant to cure before exposing it to water, and trim any excess after curing.

Limitations — where Roof & Gutter Silicone should not be used

These are the manufacturer's stated limits:

• Do not apply if the ambient or substrate surface temperature is below +5°C or above +40°C. Note that the product data table gives the application temperature as +5°C to +30°C, which is the narrower of the two figures published.
• Do not use for applications exceeding -60°C or +150°C.
• Not recommended for continuous submersion or below-waterline use. The product page adds that it is not suitable for use as a plug for burst pipes.
• It requires atmospheric moisture to cure — on non-porous substrates or in low humidity, curing slows.
• Do not use for structural glazing.
• Avoid contact with materials containing high levels of plasticisers, such as rubber and bituminous substrates.
• It is not paintable. Allow paint to dry for at least 7 days before applying the sealant on top.
• Not for use on polyethylene, polypropylene or PTFE (Teflon®).

Selleys also recommends that users conduct their own risk assessment before use, and apply a sample to the intended area to confirm appearance, finish and performance.

The bituminous and rubber warning deserves attention on roofing specifically, because bituminous membranes and flashing tapes are common on the same roofs where you would be using this sealant. Plasticisers migrate out of those materials and into the silicone, degrading the seal over time rather than immediately.

Clean up and storage

Excess sealant on tools and equipment can be removed with turps. Cured sealant can be removed mechanically or with Selleys Sealant Remover.

Store unopened packaging below 27°C in a cool, dry place away from direct sunlight, and use it within 12 months from the date of manufacture. Opened packaging may skin and form a lump near the opening — discard the lump and skin, then use the rest. If the product has been stored below the recommended storage temperature, warm it to the recommended application temperature before using it.

Colours and packaging

Roof & Gutter Silicone is supplied in 300g and 310g cartridges, with a 90mL size also listed. The published colour range is Basalt, Black, Classic Cream, Cottage Green, Deep Ocean, Dune, Galvanized Grey, Grey, Ironstone, Manor Red, Monument, Paperbark, Shale Grey, Surfmist, White, Woodland Grey and Translucent, with Colorbond® colour matches among them. Colorbond® is a registered trademark of BlueScope Steel Limited.

The 25-year guarantee

The guarantee applies when the product is used as directed, for private use, and within 12 months of purchase. It covers the product against crumbling, cracking or peeling away. If the product does not perform as specified within the warranty period, Selleys will replace the goods free of charge; to claim you must contact Selleys with details, show proof of purchase and bear the expenses incurred in making the claim. These benefits are in addition to rights and remedies under Australian Consumer Law, which cannot be excluded.

Hazard classification

Classified as hazardous under Safe Work Australia GHS 7, with the signal word Warning.

• Eye irritation — Category 2A. H319: causes serious eye irritation.
• Skin sensitisation — Category 1. H317: may cause an allergic skin reaction.

What is in it

Chemical entity	CAS number	Proportion (w/w)
2-Butanone, O,O',O"-(methylsilylidyne)trioxime	22984-54-9	1–10%
2-Butanone, O,O',O"-(ethenylsilylidyne)trioxime	2224-33-1	1–10%
N-[3-(trimethoxysilyl)propyl]ethylenediamine	1760-24-3	<1%
Non-hazardous or below reporting limits	—	Balance

The two butanone trioximes are the oxime cure system. This is a neutral cure silicone: it reacts with atmospheric moisture and releases methyl ethyl ketoxime rather than acetic acid, which is why it does not corrode the metals an acetic cure product would. On a roof that matters — Colorbond, zinc, galvanised steel and copper flashings are exactly the substrates acetic cure silicones attack.

Skin sensitisation is not irritation. Irritation settles once contact stops. Sensitisation is the immune system learning to react to the material: generally permanent once acquired, triggered thereafter by far smaller exposures, and worsening with each contact. It builds from repeated casual contact rather than one dramatic exposure, which is why gloves matter on every job and not just the big ones.

Roof and gutter work is usually a long run of bead rather than a single joint, often overhead with the cartridge above your face. Eye protection is the control people skip and the one the Category 2A classification is about.

Protection

• Gloves — nitrile rubber for intermittent contact.
• Eye protection — safety glasses or goggles.
• Ventilation — work in a well-ventilated area.
• Wash hands after use, and wash contaminated clothing before reuse.

First aid

Exposure	What to do
Eyes	Rinse cautiously with water for several minutes, removing contact lenses if present and easy to do, then keep rinsing. If irritation persists, get medical advice.
Skin	Wash with soap and water. If a rash, redness or itching develops — including hours later — get medical advice, as that may indicate sensitisation rather than simple irritation.
Inhalation	Move to fresh air. If irritation persists, seek medical advice.
Swallowed	Do not induce vomiting. Rinse the mouth and seek medical advice.

If poisoning occurs, contact a doctor or the Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand — with the container to hand. Selleys emergency line: 1800 220 770 in Australia, 0800 220 770 in New Zealand.

Common questions about Selleys Roof & Gutter Silicone

Is it safe for a rainwater tank?

It is tested to AS/NZS 4020:2018 for products used in contact with drinking water, but not all colours have been tested. Check the current test reports, available on request, for the specific colour you intend to use.

How long do I have to tool the bead?

Tooling time is 5 minutes, with a skin time of 5 to 10 minutes. Work in short sections and tool each one before moving on.

How long before it can get wet?

Allow the sealant to cure before exposing it to water. The cure rate is 2mm per 24 hours, and the product page suggests allowing around 72 hours for a full cure. If you need a faster turnaround, Roof & Gutter Speed Seal is formulated to be rain-ready in about an hour.

Why is my bead taking so long to cure?

The sealant needs atmospheric moisture to cure. On non-porous substrates such as metal roofing, or in low-humidity conditions, curing slows.

Can I paint over it?

No. It is not paintable. If the surface is being painted, let the paint dry for at least 7 days before applying the sealant on top.

Will it corrode Colorbond® or coated metal?

It is a neutral cure silicone, and Colorbond® sheet, coated metal panels and powder-coated steel are all listed as suitable substrates. Pre-test compatibility before use.

Can I use it to plug a burst pipe?

No. The product page states it is not suitable as a plug for burst pipes, and it is not recommended for below-waterline use.

Will it stick to plastic?

PVC is listed as a suitable non-porous substrate. It is not for use on polyethylene, polypropylene or PTFE (Teflon®).

How wide a joint can I seal?

Minimum width and depth is 5mm. Use a 1:1 width-to-depth ratio up to 12mm wide, and 2:1 above that, with a backer rod 25% to 50% larger than the joint width.

How do I remove old sealant before resealing?

Remove all existing adhesives or sealants before remedial work. Cured silicone comes off mechanically or with Selleys Sealant Remover.

How long does an unopened cartridge last?

The technical data gives a shelf life of 18 months, while the storage section advises using unopened packaging within 12 months of manufacture. Work to the 12-month figure.

What about fine cracks spread over a large area?

A cartridge bead is the wrong tool for that. Roof & Gutter Spray Seal is designed for fine cracks and holes over larger surface areas. The full range is on the roofing silicone page.