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. Fibreglass roofs build up surface dirt and a chalky layer as the top coat ages, and the patch needs a sound surface to bond to. Wipe the area with a degreaser, rinse, and let it dry fully. If the surface is chalky or flaking, apply a thin coat of UV Curing Primer and let it dry before you patch.
The patch is light sensitive before it cures. Keep it in its lightproof pouch 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 top coat with a light abrasion if it is flaking.
Open the pouch away from bright light. Trim the patch so it overlaps the damage by at least two centimetres on every side, and round the corners.
Peel the release film and press the patch down from the centre outward, working out any air. Press the edges firmly so nothing lifts.
Remove the outer clear film and 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. There is no curing smell and nothing to wash off.
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, 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
Ready to repair your roof?
Answer a few quick questions and we will recommend the right size and whether you need primer.
Build your order →