Emergency Roofing Repairs

How do you make an emergency roof repair to stop water damage?

Leaking roofs and gutters need to be stopped quickly, because the damage water does to ceilings, insulation and wall cavities costs far more than the repair itself. There are three distinct jobs here and two products cover all of them: Selleys Storm Sealant for leaks you have to seal now, on a wet surface or in the rain, and Selleys Roof & Gutter Silicone for flashings and prepared joints you can do properly in dry weather.

Sealing joins and gaps around the home is also worth doing for a second reason: it improves the thermal performance of the building and helps keep power bills down.

Leaking roofs, gutters and skylights

To deal with a leaking roof, gutter or skylight you need a versatile product that gives a watertight bond without being obvious. Storm Sealant delivers a waterproof seal on building materials, wet or dry, indoors or outdoors. It can be applied in the rain to stop a leak in an instant, which is the whole point of an emergency repair — you rarely get to choose the weather.

What Storm's published figures mean on a roof

Technology	Moisture-curing silyl-modified polymer (SMP), Sil-X
Packaging	290 mL cartridge, grey and black
Skin time	15–30 minutes (23°C, 50% RH)
Cure rate	2.5–3 mm per 24 hours (23°C, 50% RH)
Movement capability	±20% (ISO 9046 modified)
Full cure	Approximately 48 hours — do not disturb

These are indicative figures and are not intended for preparing specifications.

The two numbers that change how you work are the skin time and the cure. Fifteen to thirty minutes of skin time is your entire smoothing window, and it is at the short end of that range in wet weather, because the product cures on moisture. Do one section at a time and tool it before moving on. 2.5 to 3 mm per 24 hours is a depth rate — a bead pushed properly into a 6 mm gap is a two-day cure, not a one-day one — and the product must not be disturbed for approximately 48 hours even though it seals immediately.

Storm's limitations: not suitable for polyethylene, polypropylene or PTFE; not for plugging leaks subject to pressure; not paintable with solvent-based paints (use a water-based exterior paint, two coats, after cure).

Repairs to flashing

Flashings around chimneys, skylights, exhaust fans and other roof penetrations are there to keep the weather out, and sometimes they start to leak. Roof & Gutter Silicone Sealant is the recommended way to seal flashing.

Caulk the sealant out between the flashing and the roof and push it firmly into place. Tape or hold it in place until it is firm enough not to lift. That holding step matters: silicone has no green strength, and a flashing that springs back a millimetre while the sealant is still soft leaves a void exactly where the water runs.

Roof & Gutter Silicone at a glance

Technology	Neutral-cure 100% silicone, moisture curing
Tooling time	5 minutes
Skin time	5–10 minutes
Tack-free time	30 minutes
Curing rate	2 mm / 24 hours
Joint movement	±25%
Elongation at break	330% (ASTM D412)
Shore A hardness	32
Application temperature	+5°C to +30°C
Service temperature	-60°C to +150°C
Shelf life	18 months

Indicative data only, not intended for preparation of specifications.

A 5 minute tooling time and a 5–10 minute skin time is a genuinely short window, and on a roof in sun it will be shorter still. Cut the nozzle to the bead size you want before you climb up, and work in lengths you can tool inside five minutes. Tool with a clean spatula dipped in soapy water.

The ±25% joint movement and 330% elongation are what let a flashing joint survive a roof that expands in summer sun and contracts overnight. That movement capability is also why joint geometry matters: the optimum width-to-depth ratio is 2:1, minimum joint width and depth is 5 mm, joints up to 12 mm wide use a 1:1 ratio, and joints wider than 12 mm use 2:1. A bead smeared thinly across a wide gap cannot flex the way a properly proportioned one can.

Roof & Gutter Silicone suits Colorbond sheet and coated metal panels, and it is available colour-matched to a range of roof and gutter profiles as well as translucent. It carries a 25-year guarantee against crumbling, cracking or peeling away when used as directed for private use and within 12 months of purchase.

Its limitations: do not apply if the ambient or substrate temperature is below +5°C or above +40°C; do not use outside the -60°C to +150°C service range; not recommended for continuous submersion or below-waterline use; not for structural glazing; avoid contact with materials containing high levels of plasticisers, such as rubber and bituminous substrates; not for use on polyethylene, polypropylene or PTFE. It is not paintable, and if you are painting the area first, allow the paint to dry for at least 7 days before applying the sealant on top.

Repairing cracked or broken roof tiles

Roof tiles get loose, cracked or broken over time under extreme weather, and damaged tiles lead to serious water damage if they are left. Storm Sealant is suited to sealing cracks and to bonding broken tile pieces back together, giving a waterproof seal against the weather.

Work on the underside where you can, so the repair is not visible from the ground, and clean the fracture faces of dirt and moss before you bond them. Storm will go onto a damp tile, but it will not bond through a layer of loose grit.

How to apply either sealant

1. Make sure the surface is clean, sound and free of dust, oil, rust and other contaminants. On non-porous surfaces, wipe with a clean cloth dampened with isopropyl alcohol or white spirit in one direction only, then wipe immediately with a clean dry cloth.
2. Remove all existing adhesives or sealants before resealing an old joint.
3. Cut the cartridge tip, screw on the nozzle and trim it to the bead size you want.
4. Load the cartridge into a good-quality caulking gun — a high-thrust gun for these higher-viscosity products.
5. Apply a continuous bead, pushing the sealant into the joint rather than laying it across the surface.
6. Tool the bead with a clean spatula dipped in soapy water before it skins. For Storm, a spatula dipped in turpentine or white spirit within about 5 minutes.
7. Leave it undisturbed to cure — approximately 48 hours for Storm.

Clean up

Excess sealant on tools and equipment comes off with turps. Cured sealant has to be removed mechanically or with Selleys Sealant Remover, so it is far quicker to deal with the excess while it is wet.

Safety: an emergency repair is still done on a wet roof

Storm and Roof & Gutter Silicone are both classified Warning, with H319 (causes serious eye irritation) and H317 (may cause an allergic skin reaction). H317 is skin sensitisation rather than irritation: generally permanent once acquired, and built from repeated casual contact. The bead-smoothing step is where that contact happens, so tool it or glove up, particularly if you are running a long length of flashing.

Selleys Sealant Remover, named here for cured sealant, is the serious one on this page. Danger, Poison Schedule S5, Dangerous Goods Class 3, UN 1133, Packing Group II:

• H304 — may be fatal if swallowed and enters airways
• H226 — flammable liquid and vapour
• H336 — may cause drowsiness or dizziness
• H315 — causes skin irritation

H336 and this job are a bad combination, and it is worth being blunt about why. Everything on this page happens on a pitched roof, at a skylight, in a box gutter or up a ladder, frequently in rain, frequently in a hurry. Solvent-induced drowsiness or dizziness is an inconvenience on a workbench and a fall from height here. If old sealant has to be softened chemically rather than cut out, do it with your feet on the ground where the component can come down, stay upwind, and do not climb again while you feel light-headed. A valley or a box gutter has poor air movement even in the open.

H226 deserves the same care. A Packing Group II flammable liquid, plus the mineral turps used for clean-up, has no business near a flue, a solar hot-water unit, a gas appliance vent or a roof-space light fitting. Vapour from a solvent paste is heavier than air, so a roof cavity below the repair is where it will settle.

The better answer is usually not to use it at all. This page's own method for an emergency leak is to cut and scrape cured sealant mechanically and clean up with turps; Sealant Remover is for what will not come away. If the repair is temporary anyway, leave the residue and deal with it properly in dry weather at ground level.

If it is swallowed, do not induce vomiting. Rinse the mouth, give water, and get medical advice immediately. Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand.

Common questions about emergency roof repairs

Can I really seal a leak while it is raining?

Yes, with Storm Sealant. It delivers a waterproof seal on building materials wet or dry and can be applied in the rain to stop a leak in an instant.

Which product should I use on flashing?

Roof & Gutter Silicone. Caulk it between the flashing and the roof, push it firmly into place, and tape or hold it until it is firm enough not to lift.

How long do I have to smooth the bead?

Roof & Gutter Silicone has a tooling time of 5 minutes and skins in 5–10 minutes. Storm skins in 15–30 minutes and should be smoothed within about 5 minutes of applying.

When is the repair fully cured?

Both cure by moisture at roughly 2 mm (Roof & Gutter) to 2.5–3 mm (Storm) per 24 hours of depth. Storm should not be disturbed for approximately 48 hours.

Can I paint over the sealant?

Roof & Gutter Silicone is not paintable. Storm can be painted with a water-based exterior paint in two coats after curing, but not with solvent-based paints.

Can I seal a roof in cold weather?

Roof & Gutter Silicone should not be applied if the ambient or substrate surface temperature is below +5°C or above +40°C, and its stated application range is +5°C to +30°C.

Will Roof & Gutter Silicone match my roof colour?

It is available in a wide range of colours matched to common roof and gutter sheet profiles, plus white, black, grey and translucent.

How wide a gap can I seal?

Minimum joint width and depth is 5 mm. Up to 12 mm wide, use a 1:1 width-to-depth ratio; over 12 mm, use 2:1. For wide joints, use a backer rod 25–50% larger than the joint width.

Can I use these sealants below the waterline or in a pond?

No. Roof & Gutter Silicone is not recommended for continuous submersion or below-waterline use.

What about a leak in a pressurised pipe?

Storm is not suitable for plugging leaks subject to pressure. That is a plumbing job.

Will the sealant stick to a rubber or bitumen roof membrane?

Roof & Gutter Silicone should not be used in contact with materials containing high levels of plasticisers, such as rubber and bituminous substrates.

How long does the repair last?

Roof & Gutter Silicone carries a 25-year guarantee against crumbling, cracking or peeling away when used as directed for private use and within 12 months of purchase. Selleys also recommends applying a sample to the intended area first to confirm appearance, finish and performance on your particular surface.