Epoxy to fill cracks in pressure treated 4x4s

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Forum topic by GregoryF posted 06-22-2016 08:38 PM 8519 views 0 times favorited 7 replies Add to Favorites Watch
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2 posts in 1620 days

06-22-2016 08:38 PM

Topic tags/keywords: ptw epoxy resin cracks

I have just built a playset out of pressure treated pine and the 4×4’s are cracking as they dry… What product would work to fill the cracks ? Some of these cracks are quite large like 1/4 inch but the 4×4 is overall maintaining its dimensions ? I haven’t sealed it yet as I was waiting for it to dry first

I am just worried about the structural integrity of the playset as a whole… I also want to preserve it correctly for years to come… Are the cracks something to be concerned about other than filling them in ?

Thanks Greg

7 replies so far

View CudaDude's profile


179 posts in 3224 days

#1 posted 06-22-2016 09:44 PM

Don’t know how many years you are wanting to get out of it, but I built my kids a swingset from PT pine 4×4s. They split real bad but it remained structurally sound for about 5 years without even sealing it. I personally wouldn’t bother with filling the splits.

-- Gary

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8057 posts in 1628 days

#2 posted 06-22-2016 09:51 PM

if it bother you so much you can use body putty to fill them in ….. are you painting it ???

-- Tony---- Reinholds,Pa.------ REMEMBER TO ALWAYS HAVE FUN :<))

View GregoryF's profile


2 posts in 1620 days

#3 posted 06-22-2016 10:17 PM

I was going to use olympic sealer/stain … Thats great to know that the splits aren’t structurally significant !

I may not even bother with the sealing unless the wife wants it to be a different color, now that I know the splits are cosemetic only…

Thanks Guys !

View Kirk650's profile


680 posts in 1664 days

#4 posted 06-22-2016 11:46 PM

At the demands of the wife, I built an outdoor railing for the back porch. I used treated wood. It had big longitudinal cracks as the wood dried. I filled the cracks with an outdoor putty and painted the railing. Looked great. After a few wet/dry spells, the cracks reappeared. I finally gave up.

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2839 posts in 3213 days

#5 posted 06-23-2016 11:43 AM

I made a barbecue shelter with p.t. 4×4 posts. After this winter one of the posts twisted at the base with the flat face gone from say a 12 o’clock position to a 2 o’clock position. Pressure treated wood stinks.

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10861 posts in 2402 days

#6 posted 06-23-2016 12:03 PM

You can fill it and it’ll probably crack again. It’s fine.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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5951 posts in 2303 days

#7 posted 06-23-2016 12:47 PM

I don’t think that it will be a problem structurally. A cracked 4×4 is still plenty strong but if the cracks are in a place that might get touched by delicate little hands, you might want to do something to prevent splinters.

Personally, I would never use PT lumber for skin contact, especially for little ones. I know that they removed the heavy metals several years ago but I would still worry about what is in there so I would coat it with something to reduce skin contact.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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