Just use the epoxy caulk after sanding the lead paint down to bare wood

January 27, 2014 8:46 PM

After spending like six hours reading labels and talking to hardware store staff, I turn to you, AskMe. How do I patch these holes and smooth these posts in my front porch columns before painting (but after priming)?

I am dealing with:

1. A rotted out area (2" in d, sloping down to 1" depth)
2. Nail heads (some where the nail metal is still exposed, some where it's primed over)
3. That pressure-treated lumber look
4. Unevenness due to partial scraping
5. Gaps between the vertical and horizontal pieces of the railing
6. A weird triangular gap about 2-3" per side and maybe 3" deep where three railings meet

I don't want to scrape down to bare wood. Someone back in 1890 or whatever painted these posts with lead paint. Most of the actual paint seems to have been removed, but the exposed wood tests positive. To be safe and comply with our reading of current California law, we paid a lead certified crew to scrape any peeling paint and prime it. The prep work leaves a lot to be desired in my opinion, but now the whole thing is primed and should stay that way.

My question is: what product should I use for the tasks above? My (likely wrong) guesses are below:
1-3 Crawford's painters putty?
4 A few coats of Sherwin Williams Peel Stop (high build) primer?
5. Some paintable exterior caulking
6. Prime some random wood, screw it in, and put caulking around it (or live with it)

What do you think? Is there anything faster drying than Crawford's that I can use for 1-3, since it's supposed to rain soon? Thanks!

posted by slidell to Home & Garden (13 answers total)

I'd use two-part automotive body filler. Doesn't shrink on hardening, doesn't need access to air to harden, cheap. As long as what you're caulking is dry when you put it on, rain isn't going to stop it setting properly. You could even paint right over it before it's cured.
posted by flabdablet at 9:26 PM on January 27, 2014 [2 favorites]

Seconding bondo. It's cheap, it doesn't shrink, and it's moldable.
posted by zug at 11:48 PM on January 27, 2014

Err, to answer everything:

1. Bondo.
2. Pound any nails that are sticking out back in.
3. I'm not sure what this means. Could you clarify?
4. This one is tougher. My normal answer would be "sand it", but that's clearly not an option here. Your idea of thick primer is probably as good as you're going to get if removing uneven material isn't an option.
5. Bondo
6. Bondo
posted by zug at 11:52 PM on January 27, 2014

Sanding with a random orbit and a detail sander can really feather out the uneveness. Wear a good mask and maybe even pick a windy day and I think you are pretty safe. Hose down the area immediately after to settle any lead dust. Then prime again.
posted by LarryC at 11:58 PM on January 27, 2014

Yep, bondo. I used it to square off some column bases whose corners had rotted out, and it's still going strong 8 years later. The one thing my brother suggested was to drive a few screws halfway into the wood before you apply the bondo. The idea is that is gives the bondo something to hold onto, rather than just sticking to the surface.
posted by Ham Snadwich at 5:50 AM on January 28, 2014

I ran across a tutorial from the Family Handyman, which usually has good writeups. It doesn't recommend specific brands, but it does recommend types and details the process.
posted by bookdragoness at 5:57 AM on January 28, 2014 [1 favorite]

Response by poster: Are you guys suggesting this Bondo wood filler product? Technically, it should be used on bare wood, not primed surfaces. I even called their help desk to double check. Is there a Bondo product recommended for primed wood?

zug, thanks. On #2, after I hammer in the nails, what would you use to fill the hollows? On #3, I meant that the dark horizontal lines as in the image here need smoothed over somehow, because they are still showing through quite a bit. Maybe two more coats of primer would be enough, but on an interior job, I'd use spackle on both the nail holes and those indentations.
posted by slidell at 7:37 AM on January 28, 2014

This bondo (aka two-part automotive body filler, as flabdablet suggested). It has stuck to everything I've ever put it on, so I don't think you'll have to worry about it not sticking to primed wood, but test it first if you like. It's cheap and pretty easy to work with.

You can pretty much treat this stuff as outdoor spackle, if that helps you envision what to do with it. You could cover nail holes and the slots in the wood with it, if you were so inclined.
posted by zug at 9:49 AM on January 28, 2014

If their wood filler is based on similar polymer chemistry to their automotive filler, I can think of no reason why it shouldn't work at least as well.
posted by flabdablet at 8:58 PM on January 28, 2014

Response by poster: Thanks, everyone. It's nice to hear your voices of experience and have some reassurance about the bondo adhesion. Many thanks!
posted by slidell at 9:01 PM on January 28, 2014

The only reason you'd avoid using primer under Bondo would be that the Bondo is actually stronger than the primer, which makes the primer a little counter-productive. But given how well primer does stick to wood, then if you use Ham Snadwich's brother's trick of making a little porcupine of screws to hold any particularly large lumps of filler in place even if the adhesion does fail, I would expect Bondo over primer to work just fine.
posted by flabdablet at 9:03 PM on January 28, 2014

Just to clarify, the screws are only necessary when you're trying to attach an outside corner or rebuild something that broke off or rotted away. If you're just filling holes or low spots, it's not really necessary.
posted by Ham Snadwich at 10:26 AM on January 29, 2014

If you're going to fill the entirety of a "weird triangular gap about 2-3" per side and maybe 3" deep" with Bondo, as opposed to gluing or nailing in a chunk of wood and using Bondo to finish it, it probably wouldn't hurt to go the screws porcupine even if the filler will end up mostly surrounded. Wood does swell and shrink with humidity changes a little differently from cured Bondo, which for a large fill like that might eventually break the adhesion; if there are screws securing the infill back to the wood, that won't matter.
posted by flabdablet at 3:14 AM on January 30, 2014 [1 favorite]