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Bondo for fixing exterior wood trim?

Posted by rosesr4me (My Page) on
Fri, Sep 14, 07 at 14:03

My handyman repaired some wood exterior trim using Bondo rather than wood filler. I had never heard of this. What are the pros/cons of using Bondo rather than a good quality wood filler or epoxy. The house is in a southern (humid) climate.

Thanks!


Follow-Up Postings:

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RE: Bondo for fixing exterior wood trim?

The Minwax 2 part wood filler is basically bondo, so I don't think there's an issue. Whatever he used, I hope the decay was completely removed and the remaining wood was treated with a hardener. If not the repair will fail.
Ron


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RE: Bondo for fixing exterior wood trim?

The minwax filler uses the same chemical as a binder, but the filler is different.
It is much softer than bondo and easier to sand and work.


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RE: Bondo for fixing exterior wood trim?

I think it was this past month's Old House Journal (I can't check, they're packed) that had a letter from a carpenter disputing a recommendation to use Bondo for wood patching - he said it doesn't expand and contract with the wood and he gets called in to fix it. (So I guess it makes him money!) I can't remember what he said to use instead, but the issue should still be on the newsstands. Or I can come back in a couple of weeks once I get my books and stuff unpacked.

Although I haven't used it outside, I used Quikwood epoxy filler for a furniture repair and found it extremely easy to work with - it's a doughy stuff that you just knead up and use, no measuring or mixing. Our painter used glazing putty for splits/cracks, nail holes, etc. in our exterior trim this spring.


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RE: Bondo for fixing exterior wood trim?

Thank you all for responding. Sounds like I need to keep an eye on his repair since I know he did not use hardner on the remaining wood (though he did replace the damaged portion).

From now on, I will make sure he uses an actual wood filler.

Johnmari - Thanks for the Quikwood reference - I will check into that. Is it similiar to Minwax stainable wood filler (premixed)???


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RE: Bondo for fixing exterior wood trim?

It's very little like the Minwax stainable wood filler; the Quikwood is a two-part epoxy product that must be mixed (by kneading). I wore disposable gloves working with it to avoid skin reactions like dermatitis and absorbing the chemicals through my skin. It is probably closer to Minwax High Performance Wood Filler than the latex-based water-soluble filler product. Personally I have not been that impressed with any of Minwax's products, but we're lucky enough to have other options where I live (SE NH) besides the big box stores.


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RE: Bondo for fixing exterior wood trim?

I have read before that same issue..bondo does not shrink/expand same as wood and you will end up having to repair with a wood specific product. 'specially if you live in extreme weather area.There are ads for these products in This Old House magazine and the like.


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RE: Bondo for fixing exterior wood trim?

Our painter used Bondo to repair old house windowsills that were falling apart due to old age/dry rot/moisture rot damage. We thought were were going to be out MANY dollars to repair or replace those antique windows. When he was done, you could not tell there had been damage. I never expected the windows to look that good. It seems very sturdy and looks great. Only time will tell how it holds up, but it's gone a year and looks perfect.


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RE: Bondo for fixing exterior wood trim?

Many years ago when I owned a houseboat and lived on it, there was rotting wood framing in the stern sliding glass windows that made an exit to the back deck.

It would have cost a fortune to tear out the framing and rebuild it. An old salt told me to get some GIT ROT.

It is great, and saved me a lot of money. No tearing out the old rotten wood. Just get it dry. VERY DRY. Then drill or punch with an icepick into the soft wood to create channels for the compound to seep into. When it sets up, what you have is essentially epoxy-impregnated wood that looks like wood, can be painted even, and is now permanently fixed. I lived on that house boat for 10 years and never had a leak around the window again.

So I recommend GIT ROT. I saw it at a boat supply store a year or so ago. I do not work for them.


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RE: Bondo for fixing exterior wood trim?

my experience is that old house people are rather fond of bondo. i think it was the right tool for the job.


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RE: Bondo for fixing exterior wood trim?

Bondo and Minwax High Performance filler both use styrene monomer as the hardening agent with benzoyl peroxide as the catalyst to start the reaction.

The fillers are not the same however.

Bondo uses Talc and Magnesium Carbonate, while Minwax Filler uses Talc and Calcium Carbonate.

Magnesium Carbonate has a Mho's hardness of 3.5 to 4, while calcium carbonate is slightly lower at 3.

The styrene monomer after reaction is going to drive the hardness of the material also.

Having used both materials, Minwax is a lot easier to sand than Bondo.

I have replaced Bondo repairs that showed separation from the surrounding wood, and have seen other Bondo repairs nearby in the same wood that had produced cracks in the latex paint film.

I use Bondo for cars and metal and Minwax for wood.

If you catch the Minwax as it hardens you can use wood chisels to do preliminary shaping of repairs, then wait till hardening in complete to finish shaping and use sandpaper to blend the repair in.

Under a coat of primer and paint the repairs are not detectable.


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RE: Bondo for fixing exterior wood trim?

Bondo-style (polyester resins, fillers, etc) indoors only. Outdoors it sometimes will last a few years, all too often fails in two years. Two part epoxy systems that include a first step to penetrate and solidify and then a filler step have a much better track record for me. Abatron and Advanced Restoration Technology are two such systems. A.R.T has a gel epoxy that is very easy to use and extremely flexible. It has a higher unit cost than Abatron's, but you can apply the consolidant and the filler the same day; with Abatron it's strongly recommended (and I vouch for this) to allow the consolidant to cure. I also lean toward A.R.T because I have used so much Abatron I've developed a sensitivity to it.
Casey


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RE: Bondo for fixing exterior wood trim?

About five years ago, I restored three rotted window sills on a 175 year old house using several two-part epoxy products sold by a company called Rot Doctor. The products are similar to the Abatron system mentioned above. I used a liquid sealer and two fillers -- a gel that seeped into deep spaces and a paste filler for shallower spaces. After everything dried and cured, I was able to sand, prime and paint the window sills. The products are expensive and nasty to use, but the end result is fantastic. The sills are like concrete and look great after all this time.

Here is a link that might be useful: wood restoration products


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