New pressure treated 4x4 porch posts buckling or twisting

Submitted by Steiner1988 t3_115jwfv in DIY

Back in the summer i replaced rusted wrought iron posts with pressure treated 4x4s on my front porch. Today i noticed the two inner posts are badly warped or buckled. I assumed 4x4s would be sufficient enough to carry the load of the porch roof considering it only had wrought iron. I did however use the posts the day I got them from Lowes, so they were still wet.

So i guess my question is did I mess up by using wet pressure treated wood and immediately putting them under load, or are the 4x4s not sufficient enough for the load?

The porch is around 20 feet long, 7 feet wide. The posts are almost 8 feet long mounted to the bottom of the fascia boards. One post at each corner and the two inner ones evenly split. The only thing it's holding up is an old porch roof. They're sitting on a concrete porch slab. The two posts at the corners are not buckled nearly as bad as the two in the middle.

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MountainDude769 t1_j923051 wrote

Without pictures it’s hard to be certain but it sounds like everything’s fine. Pressure treated wood is usually sold pretty wet from the pressure treating process and when dried too quickly, along with natural tension in the wood, it can cause twisting and checking in the wood. Nothing to be concerned about. 4x4s are more prone to this than 6x6s or larger pieces of timber.

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mdey86 t1_j923k7s wrote

I mean, on PTL I’ve always heard “either use it the day you get it, or dry it for 3-6 months.” Either approach is fine. Using wet wood, yeah it’ll shrink a bit, but it’ll all shrink about the same amount.

The warping and buckling I don’t think is related to it being wet with treatment— drying would only make the wood shrink up a bit and maybe show some splits and cracks.

Warping and twisting is likely due to the generally poor grade of lumber sold in all big box stores. I’d suggest sniffing around your local independently owned building supply places, and maybe getting something a little beefier. 6x6’s are heavy buggers and might be overkill, but they don’t tend to warp or buckle.

If you think 6x6’s would look silly, you could always go with metal posts and then encase them in cedar 1x.

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beazzy223 t1_j93537u wrote

Replying to mdey86 (#1,858,995)

I would never build a deck with 4x4s. 6x6 or bust. The price difference is negligable and the strength difference is huge. Id only use 4x4s for railings or some other non structural scenario.

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zacmakes t1_j93aj6k wrote

Replying to Uncanevale (#1,860,503)

My takeaway from that article was that 8' 4x4's are particularly garbage (because they're always plywood veneer cores) but 10-footers are dramatically better, which is useful to know

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