How to repair a fibreglass roof
A cracked or delaminating fibreglass roof can be sealed permanently with a single Instapatch patch. This guide covers a flat or low-pitch fibreglass roof with a hairline crack, a split seam, or a small hole. The whole job takes around twenty minutes once the surface is dry.
What you will need
- Instapatch Standard, in a size that covers the damage with a margin around it
- UV Curing Primer, only if the surface is weathered, chalky or rough
- Clean cloth and a mild degreaser
- Household scissors
- A dry, reasonably bright day, or a 365nm UV lamp
Before you start
The repair area must be clean and dry. The patch needs a clean, dry, sound surface to bond to. Wipe the area with a degreaser, rinse, and let it dry fully. Primer is optional on a smooth, sound fibreglass roof. If the surface is weathered or rough, brush on UV Curing Primer and let it dry fully before you patch.
The patch is light sensitive before it cures. Keep it in its packet and only peel the film when you are ready to press it down.
Steps
Degrease and dry the crack and the area around it. Remove any loose or flaking top coat.
Shape the patch with scissors while it's still in its packet.
Peel the release film and press the patch down from the centre outward, working out any air. Press the edges firmly so nothing lifts.
If you want to paint the repair, peel off the top film now for a matt finish. Leave it on for a gloss finish that can't be painted. Expose the patch to daylight or a UV lamp. Leave it until it is hard right across.
Cure timing for this surface
On a bright day a fibreglass roof repair cures hard in around fifteen minutes in direct sunlight. In overcast conditions allow longer, or use a 365nm UV lamp for thirty to forty five minutes. The patch is fully waterproof the moment it cures.
After the repair
Once cured the patch is rigid and permanent. You can walk on it carefully, and it can be sanded smooth and overpainted with most roof coatings if you want it to blend in.
Common questions
Yes. Once cured the patch is waterproof and stays flexible enough to handle normal expansion and contraction without lifting.
Yes. Fibreglass roofs sit at normal outdoor temperatures, which is exactly what Instapatch is designed for. Clean, dry and sound substrate is all it needs to bond permanently.
Yes, if you peel off the top film straight after applying the patch. Once it has fully cured, most water based and solvent based roof paints will take to it.
Common mistakes to avoid
- Patching over a damp or dirty surface, which stops the patch bonding
- Peeling the film too early and exposing the patch to light before it is in place
- Cutting the patch too small, so it does not overlap sound material around the damage
- Skipping primer on a chalky or weathered top coat
Safety
Wear gloves and protective clothing, and only use Instapatch in a well-ventilated area. It contains polyester compound and styrene, which can irritate the eyes, skin and lungs. If it gets in your eyes, rinse them straight away with plenty of water and get medical advice. If it gets on your skin, wash it off with soap and water.
Storing spare patches
Keep unused patches on end in their original wrapping, somewhere cool, dry, dark and frost free. If a patch is very cold, warm it before use.
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