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6 Reasons Not to Use Bondo as a Wood Filler

Bondo as a wood filler

Let’s face it: wood sustains damage over time, whether from wear-and-tear or household accidents. But before you toss beloved pieces of furniture or quit your home improvement project, consider a little wood repair first.

I talk a lot about how to repair damaged wood on this blog because old houses get a lot of it. There is one thing I have been adamant about and that is not using Bondo as a wood filler, because it’s not made for that. Instead, I advocate for actual wood fillers and epoxies that were designed for wood not the auto body shop.

As if I haven’t talked about this enough yet I feel like it’s never enough because I see it so often. So today I’ve got the definitive list for you of 6 reasons NOT to use Bondo as a wood filler.

1. Conceals Wood’s Natural Beauty

Wood is used so prominently in the construction of homes, furniture, and even instruments because it’s strong and beautiful. If you use Bondo as a wood filler, however, you will conceal the natural color and markings of that wood. This means you’ll be forced to prime and paint over the surface and, in so doing, eliminate any hopes of enjoying the wood in its natural state. I guess if you’re painting then this doesn’t matter to you, but there still 5 more reasons.

2. Does Not Stain Well

Another thing that isn’t a big deal if your painting, but just so you know Bondo does not stain well…at all. It is largely impervious to water and oil-based stains so your patch stands out like a sore thumb. Trying to overcome this will only yield two different colors on your surface that serve as obvious indications you’ve made repairs.

3. Does Not Release Moisture

In most cases, wood can safely absorb a substantial amount of water before reaching a point of decay. But when the wood is suffocated by Bondo, that threshold becomes much less.

Bondo is also well-known for holding moisture; the problem is that it does so without release. And just as moisture can become trapped between metal and Bondo when performing auto body repairs, it can likewise develop between wood and Bondo. The end result can be wood rot which is likely the reason you used Bondo to begin with. Repairing rot with a material that encourages rot is the antithesis of working smarter not harder.

4. Does Not Move with Wood

When wood comes into contact with moisture, including humidity, it is going to swell and then shrink again as it dries. Architects and designers account for these movements to ensure durable wood-frame buildings and furniture.

Bondo, on the other hand, does not move. Like at all! This is highly desirable when making auto repairs, for which this substance is well-suited. But when you try to fuse Bondo and wood together, you’re likely to encounter the following scenario:

  1. Air and weather changes prompt wood to move
  2. The Bondo used to fill this wood remains constant
  3. As the wood swells and shrinks, it applies pressure to the Bondo that forces cracking
  4. Your patch is forced off the wood in short order needing re-repair

5. Poses Hazards to Your Health

Bondo came into being as a replacement for lead, used in earlier times to repair damaged auto bodies. Lead worked well for this purpose but presented two major concerns: it required extensive skill to apply and is toxic to people. Heralded for its fast drying time and easy application, Bondo is today safer than lead, but that isn’t saying much.

If you’ve ever opened a can of Bondo you know exactly what I’m talking about when I say the fumes are intense. And they’re not only intense, they are toxic because Bondo is made with fun ingredients like glass microspheres, talc powder, and titanium dioxide. You may also suffer burns if it comes into contact with your skin.

  • Nausea
  • Dizziness
  • Headaches
  • Drowsiness
  • Chest pain

Don’t all those symptoms sound like fun? I’m having chest pains just thinking about the smell. Still wanna use Bondo?

6. You Have Plenty of Other Options

This is the biggest reason not to use Bondo as a wood filler! There are so many great products on the market today from simple wood fillers to wood restoration epoxies that there is no need to Bondo anymore.

I’ve written several posts about the options you have out there and even did a 5 year field test of wood fillers and epoxies to show you some of the better options out there and how they perform.

Some of my favorites that I use every day at my restoration company are below.

Any of these products allow the wood to move as nature intended, meld well with its porous character, and reflect the same hues after staining (or painting). In short, reaching for a wood-specific filler or epoxy – not Bondo – is always a better choice.

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6 thoughts on “6 Reasons Not to Use Bondo as a Wood Filler

  1. So, when is Epoxy not Epoxy, Bondo is Epoxy, Abatron is Epoxy, JB Kwik is Epoxy. Can you explain how these Epoxies are fundamentally different, and why Bondo is any different than the other Epoxy fillers?

  2. Your points are all good.
    I do however, use Bondo for making epoxy countertops. The countertops consist of a base layer of 3/4″ plywood and the top layer of 3/4″ MDF. I stagger the plywood and MDF sheets so that the joints don’t align.

    I then use 3/4″ or 1/2″ by 1.5″ MDF strips for the edging. I apply rock-hard putty in any of the grooves between the sheets and the edging and sand it smooth. I then use a skim coat of hot drywall mud over any screw holes and sheet joints, and sand to 220 so that they are completely smooth. I only use Bondo for the edges if I am trying to make a more artistic edge; like broken stone or something similar. I don’t use the pink bondo that’s made for automobiles. I use the green or gray that is either general-purpose or designed for woodworking.

    I then coat the whole thing with one or two coats of pre-epoxy sealer before adding the epoxy color coat, clear coats and top-coat.

    I have these countertops in my house and they have held up over the years as well as any expensive countertop material and much better than laminate. I also like that I can make HUGE countertops in-place that would be cost prohibitive using any other material. My largest countertop so far is the one on my kitchen island which is 15 feet long and 5 feet wide. It looks like a single slab of soapstone, which is something I’m not sure you could get that big in real life.

  3. I would like to paint over stained cabinetry in my kitchen. It has a raised panel with routed wood in the middle, similar to bead board, but I don’t think it is. It is just routed out to look like it. Should I sand it down? Or fill it in before painting with a wood filler? I got a painter’s quote and he was going to use Bondo. So glad I read your article!

  4. Thank you! You may have just saved my life! I used Bondo to repair an old saddle and was planning on riding in it but it does not seem like a very safe idea after reading this article… I wish I would have read it before I try to fix this saddle, I guess it will just have to do as a display piece 😉

  5. Great suggestions! Thanks for all the information. I’ve read all your posts on wood fillers, and I’m filling in some exposed wood beams and siding on my 1963 Midcentury home. Durham’s has been suggested by a contractor, it’s less expensive than a lot of products. It doesn’t shrink or expand it says, but many people use it. What do you think of Durham’s?

  6. I just left a house where the wood had been repaired with Bondo. The wood was rotted all around the Bondo, probably because it couldn’t release moisture. I had to dig out a lot of rotten wood and replace it with Abatron, which Steve Quillion introduced me to. Your article bears out my experience: do NOT use Bondo as wood filler.

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