How to Fix Fibreglass on Your Vehicle

Fibreglass is durable and lightweight, but when it cracks or chips, you’ll want to repair it quickly to avoid further damage—especially in automotive applications like body panels, truck boxes, or custom parts. Thankfully, fibreglass repairs are easier than they look.

What You’ll Need:

• Fibreglass repair kit (resin, hardener, cloth)
• Mixing container and stir stick
• Sandpaper (80, 120, 220 grit)
• Disposable gloves and mask
• Scissors or utility knife
• Plastic spreader
• Primer and automotive paint (if painting after)
• Clean rags
• Wax and grease remover

Step 1:

Assess and Prep the Damage

Small cracks, holes, and delamination are usually repairable at home. Wash the area with soap and water then using a clean rag apply the wax and grease remover.  Then dry off the wax and grease remover using a clean rag.  Then sand the surface with 80-grit sandpaper to roughen it—this helps the resin bond effectively.  Tack the area with a tack cloth.

If you’re working on a hole or large crack, bevel the edges slightly with a file or sandpaper to create a smoother transition when the new material is applied.

Step 2:

Cut and Fit the Fibreglass Cloth

Measure and cut pieces of fibreglass cloth to overlap the damaged area. You’ll want to layer them—start with smaller patches, then gradually increase in size for each layer. Pre-cutting makes application much smoother once the resin is mixed.

Step 3:

Mix and Apply the Resin

Follow the instructions on your fibreglass repair kit. Mix resin and hardener thoroughly in a clean container. Using a brush or spreader, apply resin to the repair area, lay down the first piece of cloth, and saturate it with more resin. Repeat for additional layers.

Make sure there are no air bubbles trapped between layers—press gently to smooth them out. Allow the resin to cure fully. This could take several hours or overnight depending on the product and conditions.

Step 4:

Sand and Finish

Once cured, sand the surface smooth, starting with 80 grit and working up to 240 grit. Feather the edges into the surrounding surface.

If the repair will be visible, apply primer over the patch, then follow with matching automotive paint and a clearcoat, if necessary.

Step 5:

Inspect and Maintain

After repairing, keep an eye on the area to ensure the patch is holding strong. For larger panels or high-stress locations, reinforcement with backing material may be needed.

Get It Right the First Time

At Autohome, we carry everything you need for fibreglass repairs—from complete kits to colour-matched paints. If you’re unsure what product suits your project best, just ask—we’re happy to walk you through the steps.