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

Selleys Roof & Gutter Spray Seal is an aerosol sealant that seals and stops leaks in fine cracks and holes across larger surface areas. Where a cartridge sealant is the right answer for a defined joint, this is the answer for a rusty gutter seam, a hairline split in a roof sheet or a patch of pinholes spread over an area too big to bead by hand.

Its most useful characteristic is that it can be applied over wet surfaces. Roof leaks tend to announce themselves in wet weather, and a product that does not require a bone-dry substrate is what lets you deal with the problem when you find it. It is UV and weather resistant for a long lasting waterproof seal, and it is rain-ready in about two hours.

What the timings mean in practice

There are two separate waiting periods, and they are easy to confuse:

• Rain-ready in about 2 hours. This is when the applied film can take weather.
• Full cure in about 24 hours, before painting. The product is paintable after 24 hours, and that is the point at which the film is cured enough to take a coating.

There is a third, shorter wait inside the application sequence: the priming coat needs about 15 minutes to dry before you build up the sealing coats. Skipping that step is the most common way an aerosol repair sags or fails to key properly.

Because it goes on as a sprayed film rather than an extruded bead, thickness is controlled by how many passes you make, not by a nozzle cut. The manufacturer's guidance is two thick coats with drying time between them — not one very heavy coat, which may drip or sag.

Where to use it

• Roofing
• Gutters
• Skylights
• Downpipes
• Glazed tiles

The product page states that it meets the drinking water contact standard AS/NZS 4020, which matters where the guttering you are repairing feeds a rainwater tank.

How to apply it

1. Work in a well ventilated area and avoid contact with skin and eyes.
2. Clean the surface. Remove loose rust and loose material, and clean underneath the area you are sealing. Remove any pooled water if you can — the product tolerates a wet surface, but not standing water.
3. Mask surrounding areas if required to protect them from overspray.
4. Prime the surface with a light coat and let it dry, which takes around 15 minutes.
5. Hold the can about 30cm away and spray at the cracks and holes. Over larger holes you can use a mesh to bridge the gap before spraying.
6. Apply two thick coats, allowing drying time between them.
7. Allow about 24 hours for full cure before painting. The repair is rain-ready in about two hours.

Limitations — where Spray Seal should not be used

• Not for use on all plastics. The page does not name which, so test an inconspicuous area before spraying a plastic component such as a skylight dome or a PVC downpipe.
• Avoid overspray. An aerosol carries much further than a bead, and a sealant film on glass, solar panels or paintwork is difficult to remove.
• It may drip or sag if applied too thickly. This is why the method is two coats with drying time between, rather than one heavy pass.

Selleys does not publish a technical data sheet for Roof & Gutter Spray Seal, so there are no published figures for joint movement capability, service temperature, elongation or coverage. For a joint that has to accommodate measurable movement, use a sealant that publishes a movement class rather than a sprayed film.

Preparing rusted surfaces

The instruction to remove loose rust is worth taking seriously rather than treating as generic advice. A sprayed film bonds to what it lands on — if that is a flake of rust rather than sound metal, the repair leaves with the flake. Take the loose material back to a firm surface, clean underneath the area you intend to seal, and only then prime.

Hazard classification

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

• Aerosols — Category 1. H223: flammable aerosol. H229: pressurised container — may burst if heated.
• Specific target organ toxicity, single exposure — Category 3 (narcotic effects). H336: may cause drowsiness or dizziness.
• Eye damage / irritation — Category 2A. H319: causes serious eye irritation.
• Skin corrosion / irritation — Category 2. H315: causes skin irritation.

It is classified as Dangerous Goods: Class 2.1, Flammable Gases, UN 1950, proper shipping name AEROSOLS, no packing group — by road and rail under the Australian Code and New Zealand NZS5433, and also for sea transport under the IMDG Code and air transport under the IATA Dangerous Goods Regulations.

What is in it

Chemical entity	CAS number	Proportion (w/w)
Butane	106-97-8	10–30%
Propane	74-98-6	10–30%
Cyclohexane	110-82-7	10–30%
Naphtha, petroleum, hydrotreated heavy	64742-48-9	1–10%
Ingredients determined to be non-hazardous or below reporting limits	—	Balance

This is the one product in the roofing range that is a dangerous good, and the reason is the can, not the sealant. Every cartridge roof and gutter silicone beside it on the shelf is undeclared for transport. Put the same job in an aerosol and you add butane and propane propellant at up to 30% each, plus cyclohexane at up to 30% as solvent — on the stated ranges, as much as ninety per cent of what you are spraying can be flammable hydrocarbon that then evaporates. That is what H223 flammable aerosol and Class 2.1 describe. It also means every ignition source matters: no grinder, no hot works, no cigarette, no soldering iron anywhere near where you are spraying or where the vapour is draining to. Vapour from these gases is heavier than air and will run downhill along a gutter or into a roof cavity.

H229 — pressurised container, may burst if heated — is the sleeper on a roofing job. The storage instruction is not to expose the can to temperatures above 50°C, and a dark metal roof in the Australian sun, a ute tray, or a closed vehicle parked on site will all exceed that comfortably. The can you leave beside you while you work up the run is the can sitting in full sun on hot steel. Keep it in shade, and take it out of the vehicle at the end of the day.

The narcotic-effects classification is about where you are spraying, not how much you use. H336 is drowsiness or dizziness from a single exposure — the cyclohexane and naphtha vapour. The page already tells you to work in a well ventilated area; this is the reason. A box gutter, the underside of an eave, a skylight well or a roof cavity is a confined space with a person in it, and the method here is two thick coats from 30cm, which puts your face in the plume for a sustained period. Impairment while you are on a roof is a fall risk before it is a health risk.

The overspray warning already on this page has a second half worth stating: whatever misses the gutter is a mist you are standing in. Spray with the wind behind the work rather than in your face, wear eye protection — Category 2A serious eye irritation, and an aerosol reaches an eye far more easily than a bead does — and use a respirator if you cannot get real air movement through the space.

Protection

• Eye protection — safety glasses or chemical goggles.
• Respirator — a suitable respirator is specified; use one wherever ventilation is limited.
• Gloves — nitrile rubber is indicated as suitable for intermittent contact; glove construction and site conditions vary, so make the final assessment yourself.
• Clothing — overalls or protective clothing, and safety shoes or rubber boots.
• Ventilation — use only outdoors or in a well-ventilated area; avoid breathing dust, fume, gas, mist, vapours or spray.
• Storage — cool, dry, well-ventilated place, out of direct sunlight, and never above 50°C. Keep away from sources of heat and ignition.
• Wash hands before smoking, eating, drinking or using the toilet, and wash contaminated clothing before storing or re-using it.

First aid

Exposure	What to do
Inhalation	Move the person out of the exposure immediately without becoming a casualty yourself. Remove contaminated clothing and loosen the rest, let them settle into the most comfortable position and keep them warm and at rest until fully recovered. Seek medical advice if effects persist. Do not let anyone who has become drowsy or dizzy go back onto a roof or a ladder.
Eyes	Rinse cautiously with water for several minutes. Remove contact lenses if present and easy to do, then keep rinsing. If eye irritation persists, seek medical advice or attention.
Skin	Wash the affected area immediately with plenty of soap and water.
Swallowed	Rinse the mouth with water. Do not induce vomiting. Give a glass of water to drink. Never give anything by mouth to an unconscious person. If vomiting occurs, give further water 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 Spray Seal

Can I use it while the roof is still wet?

Yes, it can be applied over wet surfaces. Remove pooled water first if you can.

How soon can it rain?

It is rain-ready in about two hours.

When can I paint over it?

After about 24 hours, when it has fully cured. It is described as paintable after 24 hours.

How far from the surface should I hold the can?

About 30cm.

Do I need a primer coat?

Yes. Prime the surface with a light coat and let it dry for around 15 minutes before applying the sealing coats.

How many coats?

Two thick coats, with drying time allowed between them.

What about a hole too big to bridge?

The directions suggest using a mesh over larger holes before spraying.

Will it work on plastic?

It is not for use on all plastics. The page does not specify which, so test first on an area that will not show.

Why is my repair sagging?

It has probably been applied too thickly in one pass. The product may drip or sag if applied too heavily — build it up in two coats instead.

Is it safe for a rainwater tank?

The product page states that it meets the drinking water contact standard AS/NZS 4020.

Can I use it on skylights and downpipes?

Both are listed applications, along with roofing, gutters and glazed tiles. Bear in mind the plastics caution if the component is plastic.

What if I need to seal a defined joint rather than a spread of pinholes?

Use a cartridge product. Roof & Gutter Silicone and Roof & Gutter Speed Seal are the neutral cure silicones in the same family; the full roofing silicone range lists the alternatives.