is bondo wood filler waterproof?

Bondo is a filler that can be used to repair small dents and holes in cars. It’s made from a mixture of polyester resin and glass microspheres, which gives it a texture similar to toothpaste.

Bondo is also available in different colors so you can match your car’s paint job when filling in dents. You might have heard that Bondo isn’t waterproof, but there are many issues with this claim.

First off, what does “waterproof” mean anyway? Does it mean it won’t get wet? Or does it mean water won’t seep into the wood underneath the Bondo? These are two completely different things! So let’s explore how waterproof Bondo really is…

Is Bondo filler waterproof?

Bondo filler is not waterproof. It’s a wood putty that can be used to fill holes in wood surfaces and add strength to them. Water will get into the wood if it’s wet, but Bondo doesn’t keep water out of the wood after it has dried.

Does Bondo seal wood?

If you’re looking for a waterproof wood sealant, Bondo is not the answer. You’ll want to use another product (such as Sikaflex) that can be used on exterior surfaces.

Bondo is not particularly good at sealing wood because it’s designed to fill gaps in damaged areas of your car where water usually isn’t present.

If you’re using it for spot repairs or filling holes in an exterior wall, however, then you may want something else—and we’d recommend using Sikaflex instead.

Is wood filler waterproof when dry?

Yes. Bondo is waterproof when dry, but not before that. If you’re planning on using Bondo to fix a hole in your deck or make a new part for your boat, then it’s important that you understand how long it takes for the wood filler to cure so you know when it will be waterproof.

Bondo dries slowly because of its high oil content and it won’t become completely hard until all of that oil has evaporated out of the surface of the wood filler.

That means that if you apply too much Bondo at once, or if there are any spots where there isn’t enough ventilation in your project area (like under an overhang), then leaving those areas exposed to high heat could cause some serious issues with leaks later on down the line!

Is Bondo wood filler different than regular Bondo?

Bondo is a brand name for polyester resin filler, which is a two-part epoxy resin. Bondo wood filler is also known as polyester putty, polyurethane filler, or polyester resin.

  • Bondo can be used on metal and plastic surfaces like cars, motorcycles, boats, and other vehicles.
  • It was invented in the 1930s by Joseph Bufano who was working at the time for Ford Motor Company.

Is Bondo wood filler an epoxy?

No, Bondo is not epoxy.

Bondo is a two-part polyester resin that comes in several varieties: Wet sandable (for fine finishing), Heavy Duty Extra Hardener, and Thick Bondo.

The types of Bondo you need depend on the kind of project you’re working on, but all varieties can be used as filler and sealer in addition to being paintable.

What will Bondo not stick to?

Bondo will not stick to the following:

  • Rubber, vinyl, or plastic surfaces
  • Glass or metal surfaces (including aluminum)
  • Concrete or stone surfaces that have been sealed with a wax or oil sealant

Will Bondo stop wood rot?

Bondo is not intended to be used as a wood rot repair product, nor is it waterproof. Bondo is a wood filler and patching material that can be used to fill holes in drywall, plastic, metal, and other hard materials.

It’s not intended to be used as a sealant or waterproof barrier for the outdoors; however, you can use Bondo over existing coatings such as exterior paint or stain if you need to fill in an area where your current paint job has worn down.

However, when using Bondo on outdoor projects such as decks or fences, make sure that your surface is clean and dry before applying the product.

Can you use Bondo to fix rotted wood?

Bondo is not a waterproof product, so it won’t stop wood rot. It will, however, provide an excellent base for a paint job or varnish if the wood is in good condition.

Bondo is much easier to apply than regular epoxy because it comes in a putty form, rather than liquid. You can also use Bondo on metal or other surfaces as long as they are not porous.

If you want to restore rotted wood with Bondo and keep it looking like new for years to come without having to re-stain every few months, use regular epoxy instead.

The longer-lasting coat will cost less money and be easier on your time while still giving you great results!


Now that you know about Bondo wood filler, you can use it to repair your wood and make it look new again. This product is easy to use, affordable, and available at most hardware stores or online.

You can even find DIY tutorials online if you don’t feel comfortable using this product on your own!

Photo of author

Martin Flood

Martin Flood has been working in the construction industry for over 20 years as a general contractor with expertise in remodeling projects that are large or small. He has furthered his career by specializing in epoxy resin flooring, providing excellent service to both commercial and residential clients. Martin’s experience enables him to offer professional advice on how to choose the right type of project based on your needs and budget.

Leave a Comment