Rotten Redwood Repair with Fix-it-all?

Question

In the past I have repaired rotten siding and window trim with fix-it-all. The benefit is it can be sculpted to match the profile of difficult to find trim and can fix rotten patches of wood siding (up to a few inches in diameter) without pulling anything off the house. I did this a few years ago and it still looks good as new, but I recently read that its not recommended to use fix-it-all on the exterior of the home because it can absorb the moisture in the air and further rot the wood.  I would think as long as I prime and paint over it, it would keep the moisture out. Has anyone used this product 10+ years ago on outside wood repairs?  How has it held up? Are there any other products you would recommend instead? located in a wet area on the coast of northern California.

Scott Davis · Answer

fix-it-all (joint compound with some additives) is not suitable for exterior at allYes it will wick in water as the paint deteriorates, and cause more rot, and keeping a good coat of paint on it won't be enough long-term in many/most climates.bondo (polyester auto body resin) is a cheap-ish "alternative", although harder to get detail work just right and not really all that suitable anyway (maybe ok with a good epoxy / primer, perhaps?). the reason not to use bondo is the main ingredient talc isn't a good choice. the next class of products that ARE suitable use better filler ex microbaloons or something else not talc."bondo glass" (also polyester resin, talc with fiberglass cloth strands) & similar   is the "lowest" group of products I would even remotely consider for exterior/occasional water exposure. But it's still a bandaid and will pop out, crack, let water in, separate, and let the underlying wood rot almost as bad as regular bondo, after a few years.Napa, 3m, bondo, & Evercoat (marine), etc all sell polyester auto body fillers that are one step up from the prior with real "waterproof" claims etc, maybe priced around $30-50/quart or $75/gallon, range. These products may hold up for a decent number of years, but of course, prep work is still key. Still a bandaid, meant to get you by for a handfull of years or cosmetic fix only somewhere fairly dry.  Sounds like a situation where splicing in a new piece of wood would be a better longterm choice , overall. Finally, 2-part epoxy fillers though expensive are the best choice for exterior, for example west systems with microbaloons. Correct prep work still required. A permanent repair, have to address the reason it rotted in the first place of course.The labor cost is the same, I know what product's I'd use

Marshall Rousseau · Answer

@Albert Braun Thanks for the rely. Sorry I just saw this now. I think presto patch is exactly the same stuff as fix-it-all.  I started using bondo wood filler for similar external uses.  It's more expensive and more of a pain to work with than fix-it-all, but it's supposed to hold up better.  I'll check out some of the other products you mentioned.  Thanks!

Albert Braun · Answer

Thanks for sharing the idea that Fix-It-All absorbs water and can promote rot in the wood it contacts. Interesting. Sounds plausible to me. But I'm sorry to say that I lack experience with that in a very damp climate like Northern California's coast.

I read somewhere that Fix-It-All lasts about as long as the paint around it does. So, IMHO, if you really really want to use Fix-It-All outside, the approach you mentioned sounds reasonable: prime the wood first, patch with Fix-It-All, sand and then prime and paint. I don't know how you could do any better than that with Fix-It-All. In any case, it's my understanding that the original Fix-It-All compound has been pulled off the market by its manufacturer. (There is still a roughly similar product called Presto Patch though). That said there are other more expensive products like MH Ready Patch (original formula with high VOC levels if you can find it), Synko Patch and DAP Platinum Patch which are designed for both interior and exterior use on wood, plaster, masonry, etc. (BTW, I have a hypothesis that because it smells so bad and is full of VOCs, original formula MH Ready Patch is repellent to boring and wood-eating insects, but that's just my wild guess). Another nice thing about these products is that they give you more working time than Fix-It-All.

Unfortunately these do cost more and tend to dry out in the can, causing waste. Once you start using it, keep a piece of plastic on top of the remainder inside the can, and also seal the can tightly with the lid. You may find it best to buy multiple pint sized cans rather than a single large can. Then again, every time I mix up a batch of Fix-It-All I end up wasting a bunch of it, too. Finally, there's a different powdered product named "OnePass" by RapidSet. I have never used it, but the box says it's good for interior/exterior applications. It's more of a joint compound for plaster work though. If you want to use it to patch wood, you would need to experiment and see how it performed.

Good luck!