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I got some fence pickets for a small, outdoor project (a garden box, something like this).

They are super wet (I literally get sprayed when cutting on a tablesaw!) and SUPER soft - with a little wiggling I can pull a #8 screw right out of the board. The boards are only 5/8" thick, so when screwing two of these together a 1 1/4" countersunk screw pokes out the other side, so I'm only using 1" screws.

Is there some trick to fastening these so they won't pull apart? I'm planning to put a few bags of soil into this box and I'm afraid the weight will just rip all of the screws out.

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    Are they pressure treated? Lean them up against the garage wall for a week to dry out. – Chris Cudmore Oct 31 '19 at 14:43
  • Yes, they are pressure treated. Ok so you think once they dry out they will behave more like "normal wood" and hold screws much better? – David Doria Oct 31 '19 at 14:45
  • Yes. They spray them with the chemical and ship right away while the boards are still wet. On a fence, it really doesn't matter, as the board is mounted in near ideal drying conditions. – Chris Cudmore Oct 31 '19 at 14:50
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    Pressure-treated lumber isn't sprayed. It's fully immersed in a tank under extreme pressure so that the treatment goes to the core of the board. – isherwood Oct 31 '19 at 14:53
  • Are you going to have separation between the soil and the pickets? Otherwise the pressure treatment can leach into the soil, which can be toxic. – gbronner Oct 31 '19 at 15:40
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As you suspect, pressure-treated lumber holds fasteners much better when it dries out somewhat. That would take some time, though, as you don't want to rush it or you'll get severe warping.

If you're in a hurry, switch to something like 1/4" carriage bolts. They don't depend on thread grab and will hold better in the long run anyway.

Otherwise go to a heavier screw. A #12 has several times the thread area and will hold much better.

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  • I agree with the carriage bolts especially since you're building the planter which appears will be elevated. – JACK Oct 31 '19 at 15:28

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