Pressure Treated Wood

[Robert Langlois]

I was moving a wood pressure treated (PT) fence over a few feet and tried to remove one of the 4x4 PT posts. It snapped right at ground level where there was a knot. I have noticed that this PT spruce does not absorb the copper salt very deeply and has almost no absorption into the harder close grained knots. The packing around the post was ground-up and recycled concrete which packs up quite hard.

Would it be better to char or coat the wood with tar next time?

[Cliff Rohrabacher]

I have soaked wood in used motor oil with good results. But it's gotta be dry. They used to boil wood in tar to get it to penetrate in.

[Don Abele]

Robert, over the past three years I've used A LOT of ACQ PT lumber. I built a 10x20 front porch, a 15x30 back deck, and installed over 800 feet of two rail, split rail fence. Every time I cut the stuff (2x4, 2x6, 2x8, 2x10, 2x12, 4x4, 6x6) I was amazed at how the ACQ went all the way through. The sickly green color was through and through. Maybe my lumber supplier (not a Borg) has a better supplier, don't know, but I've had no problems with the stuff I've used.

As for PT and concrete, I've always been told that's a big no-no, no matter how well preserved. My porch and deck are sitting on concrete pilings with galvanized stand-offs. The fence posts are four feet in the ground (three above) and surrounded with packed 3/4" gravel and dirt, no concrete.

I would not advocate using tar or oil...they stopped using it because it leaches into the ground and can be almost as bad as the old arsenic treated PT lumber. Besides, it's messy and smelly!

Be well,

Doc