Sealing Stainless Steel Gutters

Can Selleys Roof & Gutter Grey Silicone be used to seal gutters made from stainless steel?

Yes. Any of the Selleys Roof & Gutter Silicones will be fine to use on stainless steel guttering.

Stainless steel is one of the substrates listed on the Roof & Gutter Silicone technical data sheet, alongside aluminium, mild and galvanised steel, powder-coated steel and PVC. The grey is one of a wide range of colours, and the choice of colour does not change the product's adhesion.

Why neutral cure matters on stainless steel

This is the technical reason the answer is a confident yes rather than a qualified one.

Selleys Roof & Gutter Silicone is a neutral cure, 100% silicone sealant. Neutral cure products set without releasing acetic acid. Acetic cure silicones — the ones with the sharp vinegar smell for the first day — release acid as they cure, which is why they are used on glazed tile and glass rather than on metals.

On stainless steel that distinction matters. Stainless steel's corrosion resistance comes from a thin passive chromium oxide layer on its surface. Neutral cure chemistry avoids putting an acid against that surface as the bead sets. It is also why the same product is specified for Colorbond sheet and coated metal panels, where an acid cure product could affect the coating.

Published figures

Property	Roof & Gutter Silicone
Technology	Neutral cure, 100% silicone
Specific gravity	1.04
Joint movement	±25%
Slump	0mm
Shore A hardness	32
Tooling time	5 minutes
Skin time	5–10 minutes
Tack-free time	30 minutes
Cure rate	2mm / 24 hours
Elongation at break	330% (ASTM D412)
Modulus at 100% elongation	0.6 MPa (ASTM D412)
Application temperature	+5°C to +30°C
Service temperature	−60°C to +150°C
Shelf life	18 months
VOC	33 g/L
Standards	AS/NZS 4020:2018 for products in contact with drinking water (not all colours tested)
Guarantee	25 years against cracking and peeling

Indicative data only, not intended for the preparation of specifications.

What the numbers mean in a gutter

Zero slump is genuinely useful here. A gutter joint is often sealed with the gutter in place and the bead applied to a vertical or overhead face. A sealant that does not slump stays where you put it rather than sagging out of the joint before it skins.

±25% movement capability covers the thermal movement of a metal gutter run, which expands and contracts noticeably between a cold night and a hot afternoon.

Service temperature to +150°C is far beyond anything a gutter sees, which is a useful margin on a dark roof in summer.

The AS/NZS 4020:2018 listing matters if the gutter feeds a rainwater tank. That is the standard for products used in contact with drinking water. Note the caveat on the data sheet: not all colours have been tested, and current test reports are available on request. If the water is being collected for drinking, confirm the specific colour with Selleys on 1300 555 205 rather than assuming.

Preparing a stainless steel gutter joint

1. Make sure the surfaces are clean, dry, sound and free of dust, oil, rust and other contaminants.
2. Clean the non-porous metal with a clean cloth dampened with IPA or white spirit, wiping in one direction only, then immediately follow with a clean, dry cloth. Wiping back and forth just redistributes the contamination you have lifted.
3. Remove all existing adhesives or sealants before sealing over remedial work. Nothing new bonds to old sealant.
4. Cut the cartridge tip, screw on the nozzle and trim it to the bead size you want.
5. Use a good quality gun — a high thrust ratio helps with a high viscosity product.
6. Apply a continuous bead to the joint, pushing the sealant into it rather than laying it across the top.
7. Tool the bead with a clean spatula dipped in soapy water before the skin forms, which is within about 5 minutes.
8. Clean excess off tools and equipment with turps. Cured sealant can be removed mechanically or with Selleys Sealant Remover.

Joint sizing for a lap or a formed joint

• Optimum width-to-depth ratio: 2:1.
• Minimum joint width and depth: 5mm.
• Widths up to 12mm: 1:1 ratio.
• Widths greater than 12mm: 2:1 ratio.
• Backer rod: 25%–50% larger than the joint width.

On a 5mm-wide, 5mm-deep joint, a 300mL cartridge covers roughly 12 metres and a 600mL cartridge about 24 metres — add 10–15% for wastage.

Limitations

• Do not apply if the ambient or substrate surface temperature is below +5°C or above +40°C. A metal gutter in full sun exceeds 40°C well before midday in summer.
• Not paintable. Allow paint to dry for at least 7 days before applying the sealant over it.
• Not recommended for continuous submersion or below-waterline use. A gutter that holds standing water permanently is at the edge of this.
• Not for use on polyethylene, polypropylene or PTFE. Pre-test compatibility with other substrates.
• Avoid contact with materials containing high levels of plasticisers, such as rubber and bituminous substrates, which can migrate into the sealant and cause staining or reduced performance.
• Not for structural glazing.
• Requires atmospheric moisture to cure. On non-porous substrates like stainless steel, or in low humidity, curing is slower than the published rate.

Safety: the removal step is the hazardous one, and it happens on a ladder

Roof & Gutter Silicone itself is a mild product — classified with the signal word Warning for eye irritation and skin sensitisation. The product that changes the picture is the one in step 8, for taking a cured bead off before you reseal.

Selleys Sealant Remover carries the signal word Danger and Poison Schedule S5, with 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 Dangerous Goods Class 3, UN 1133, Packing Group II.

H336 is the one that matters most on a gutter. Everywhere else, "may cause drowsiness or dizziness" is a nuisance classification. On a ladder or a roof edge it is the whole risk. The method — spread a 5 mm layer of remover, leave it at least 10 minutes, scrape it back — means standing over an open, evaporating surface for a quarter of an hour, usually with your face a forearm's length from it, often in a gutter run where a fascia and a roof edge trap the air. Do the dwell time from the ground if the section can be taken down; if it cannot, come off the ladder while it dwells rather than waiting up there.

H226 needs a second thought on a metal roof. This page already warns that gutter metal passes 40 °C well before midday. A flammable-liquid tub should not be left on hot sheeting or in the sun on the roof while you work, and it should not be near a flue, a solar hot water unit or a rooftop condenser.

H304 is why the tub stays in its own container and never gets decanted, and why vomiting must not be induced if any is swallowed — that is the product's own first aid. H315 is why the gloves the directions ask for are nitrile rather than cotton.

The lower-hazard route: the page's own alternative of removing cured sealant mechanically carries no classification. On a short run of gutter, a knife and a scraper avoid the solvent entirely.

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

Common questions about sealing stainless steel gutters

Does the colour affect performance?

Not adhesion. It does affect the drinking water certification — not all colours have been tested to AS/NZS 4020:2018, so check if the gutter feeds a drinking water tank.

Do I need to prime stainless steel?

No priming is specified. What is specified is cleaning with IPA or white spirit, in one direction, followed by a dry cloth.

Will an ordinary bathroom silicone do?

The wet-area silicones are formulated for a different job and No Mould is not suitable for metals other than aluminium and stainless steel — but they are not UV and weather products in the way the roofing silicone is. Use the roofing product outdoors.

Can I seal a gutter that is still wet?

No. Surfaces must be clean and dry. A wet joint will not bond.

How long before rain?

Skin time is 5–10 minutes and tack-free time is 30 minutes. The skin sheds water; full cure runs at 2mm per 24 hours through the bead.

How much do I need?

For a 5mm × 5mm joint, about 12 metres per 300mL cartridge. Add 10–15% for wastage.

What about galvanised or Colorbond gutters?

Both are covered — the data sheet lists mild and galvanised steel, powder-coated steel and Colorbond sheet among suitable substrates.

Can I seal over an old bead?

No. Remove all existing adhesives or sealants before applying new product on remedial work.

What if the gutter is leaking at several small holes rather than a joint?

See Roof & Gutter Spray Seal, which is made for fine cracks and holes over larger surface areas, and emergency roofing repairs.