Can You Use Bondo Filler for Fiberglass Doors at Home?

Bondo Body Filler is a typical two-part putty compound that is used for repairing scratches, dents, dings, holes, rust, and other minor flaws in the vehicle’s exterior body.

Originally marketed as an automotive body filler, it’s presently also a commonly used product for repairing fiberglass materials in the home and marine industry.

The reason why Bondo products such as body filler are becoming a top favorite for household repairs is that it’s branded by 3M for their line of American-made products.

And yes, you can use it for repairing the cracks or holes in your fiberglass doors, windows, and trims at home.

Based on my personal experiences, the biggest advantage of using Bondo over a regular wood filler or polyester filler is its very short drying time.

While a wood filler can take hours to dry, Bondo filler will mostly dry in less than 30 minutes.

Also, unlike wood filler which requires more than one coat, you can get the door repairing job done using Bondo with only a single coat.

Few other properties that make Bondo filler an ideal choice for fiberglass doors are its non-shrinking, waterproof, and permanently durable after it gets cured on the surface.

And not to mention, you can even use it for repairing surfaces made of materials like alloys, wood, as well as concrete.

Using Bondo for Fiberglass Doors

Fiberglass entry doors are becoming a great alternative to wood doors due to the variety of different advantages it offers.

The major one is – that, unlike wood, it does not warp, crack, or rot very soon with changes in climatic conditions or due to other environmental factors.

Doors made of fiberglass are also superior to metals like steel because they don’t rust, scratch, or corrode with time.

With that said, fiberglass doors are still prone to getting cracks due to cold, wind, rain, and sun, especially the ones used outdoors.

To fix and repair the cracks, you can use the Bondo for fiberglass by following the steps given below…

1. From your Bondo kit, mix the filler and the hardener on a clean piece of plastic or glass.
2. Mix the hardener and Bondo filler material thoroughly until the mixture reaches a uniform color
3. With a plastic spreader (included with the Bondo kit), spread the mixed filler over the area to be repaired.
4. Apply the filler in not more than a ¼-inch thick layer; make sure you remove the excess filler with a clean piece of rag by wiping it in one direction.
5. Allow the filler to dry and cure for about 10 to 15 minutes; once dried and sealed, you can sand the surface lightly and apply the desired finish like paint or stain

Tips and Warnings

Although Bondo Fiberglass Resin filler is sandable, you should not sand the surface hard.

For sanding, wait for at least an hour to dry the filler and use fine-grit sandpaper or steel wool.

If you need to refinish the door with a paint or stain, select the product that is designed for the project.

There are products such as Bondo all-purpose putty, Bondo metal-reinforced filler, and a few others available on the market.

While they can work, it’s good to choose the one that is specifically meant for fiberglass.

Final Thoughts

Fiberglass material is built to last and can stay in top shape, provided you fix the minor scratches and cracks with Fiberglass Bondo from time to time.

Since complete replacement of fiberglass doors can be very expensive, I recommend performing at least a yearly maintenance that will not only help fix the damaged fiberglass panels but also prevent them from getting worse and irreparable.

Bondo filler for plastic is one good product that can help fix the issues related to gaps, holes, and cracks in the fiberglass doors and windows.

Just make sure you use the right product and follow the right process.