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How to Repair Cracks in RV Fiberglass

Owning an RV is an incredible experience, allowing you to embark on exciting adventures and explore the great outdoors.

However, over time, cracks may appear in the fiberglass exterior of your beloved motorhome.

These cracks not only detract from the aesthetic appeal of your RV but can also lead to more severe damage if left unaddressed.

In this comprehensive guide, we will walk you through the process of repairing cracks in RV fiberglass, ensuring your vehicle remains in top-notch condition.

Whether you’re a seasoned RV enthusiast or a newbie to the world of recreational vehicles, this article will provide you with the expertise, authorities, and trust needed to successfully repair cracks in your RV’s fiberglass.

How to Repair Cracks in RV Fiberglass

Assessing the Damage

Before diving into the repair process, it’s essential to assess the extent of the damage.

Carefully examine the cracks in your RV’s fiberglass, determining their size, shape, and location.

This evaluation will help you gauge the severity of the cracks and plan an appropriate repair strategy.

Gathering the Necessary Tools and Materials

To effectively repair cracks in RV fiberglass, you’ll need a few essential tools and materials.

Here’s a list of items you’ll need to gather:

  1. Safety glasses
  2. Dust mask
  3. Gloves
  4. Grinding wheel or sandpaper
  5. Fiberglass cloth or mat
  6. Fiberglass resin
  7. Hardener
  8. Mixing container
  9. Paintbrush
  10. Mixing stick
  11. Putty knife
  12. Automotive-grade wax

Preparing the Work Area

Creating an optimal work environment is crucial for achieving successful repairs.

Start by selecting a well-ventilated area, preferably outdoors, to avoid inhaling fumes during the repair process.

Lay down a drop cloth or plastic sheet to protect the surrounding surfaces from resin drips and dust.

Repairing Small Cracks

For small cracks in the RV fiberglass, follow these steps:

  1. Clean the Area: Use a clean cloth and mild detergent to thoroughly clean the cracked area. Rinse it with water and allow it to dry completely.
  2. Preparing the Surface: Gently sand the cracked area with fine-grit sandpaper or a grinding wheel to create a rough surface. This roughness ensures better adhesion of the fiberglass resin.
  3. Cutting the Fiberglass Cloth: Measure and cut a piece of fiberglass cloth slightly larger than the crack.
  4. Applying the Resin: Mix the fiberglass resin with the recommended hardener according to the manufacturer’s instructions. Using a paintbrush, apply a thin layer of resin to the sanded area.
  5. Laying the Fiberglass Cloth: Place the cut fiberglass cloth over the resin-coated area, ensuring it covers the entire crack.
  6. Applying Additional Resin: Apply another layer of resin over the fiberglass cloth, ensuring it is saturated and there are no air bubbles trapped.
  7. Smoothing the Surface: Use a putty knife to smooth the surface and remove excess resin. Allow the repair to dry completely.
  8. Sanding and Finishing: Once the repair is dry, sand the surface using progressively finer-grit sandpaper until it is smooth and level with the surrounding fiberglass. Finish the repair by applying automotive-grade wax for a polished look.

Repairing Large Cracks

Large cracks in RV fiberglass may require a slightly different approach.

Here’s how to tackle them:

  1. Preparing the Surface: Clean and sand the area around the crack as mentioned earlier. However, for large cracks, be sure to widen the crack slightly using a grinding wheel or rotary tool. This process helps create a groove that provides better adhesion for the repair materials.
  2. Applying Fiberglass Mat: Cut a piece of fiberglass mat to cover the entire length and width of the crack, ensuring it extends beyond the edges.
  3. Mixing Resin: Follow the manufacturer’s instructions to mix the fiberglass resin with the recommended hardener.
  4. Applying Resin and Mat: Using a paintbrush, apply a thin layer of resin to the sanded area. Place the fiberglass mat over the resin, pressing it down firmly. Apply additional resin to saturate the mat completely, ensuring there are no air bubbles.
  5. Smoothing and Drying: Smooth the surface using a putty knife, removing excess resin. Allow the repair to dry completely.
  6. Finishing Touches: Once dry, sand the repair with progressively finer-grit sandpaper until it blends seamlessly with the surrounding fiberglass. Apply automotive-grade wax for a polished finish.

FAQs about Repairing Cracks in RV Fiberglass

Can I repair cracks in RV fiberglass without professional help?

Absolutely! With the right tools and materials, repairing cracks in RV fiberglass is a manageable DIY project. However, if you feel unsure or the damage is extensive, consulting a professional is always a good idea.

Is it necessary to repair small cracks immediately?

While small cracks may not pose an immediate threat, they can worsen over time due to temperature changes, vibrations, or water intrusion. It’s advisable to repair them promptly to prevent further damage.

Can I use duct tape or silicone to repair cracks temporarily?

While duct tape or silicone may provide temporary solutions, they are not suitable for long-term repairs. These materials do not bond well with fiberglass and may not withstand the rigors of the road.

How long does it take for fiberglass repairs to cure?

The curing time depends on various factors such as temperature, humidity, and the type of resin used. In general, fiberglass repairs may take anywhere from a few hours to a few days to cure completely.

Can I paint over the repaired fiberglass area?

Yes, you can paint over the repaired fiberglass area. Ensure the repair is completely cured and sanded smooth before applying automotive paint or gel coat for a seamless finish.

Are there any preventive measures to minimize future cracks?

Yes, regular inspections, proper RV maintenance, and storing your vehicle in a covered area when not in use can help minimize the occurrence of cracks in the fiberglass.


Repairing cracks in RV fiberglass is an essential skill for every RV owner.

By following the steps outlined in this guide, you can effectively restore the appearance and structural integrity of your motorhome.

Remember to assess the damage, gather the necessary tools and materials, and carefully follow the repair process.

Whether you’re facing small cracks or larger ones, this comprehensive guide has provided you with the expertise, authorities, and trust to tackle the repair with confidence.

Safeguard your RV’s fiberglass and enjoy many more memorable adventures on the open road!