Just found out pressure treated lumber from 2004 has way less copper than the stuff we get today

I was reading an old Fine Homebuilding issue from my dad's shop last night and saw the retention levels were nearly half of what the modern stuff is, so if you're reusing old deck boards for a shed floor like I was planning, your fasteners might last longer than you think - has anyone else looked into this for their own projects?

3 comments

3 Comments

kellyjones11d ago

I was planning to reuse old deck boards for a shed floor" - that's exactly the kind of project where people forget about the chemical changes over time. My question is: have you actually tested the copper levels yourself, or are you just going off the 2004 spec card? Because lumber that sat outside for 20 years could have leached a lot of that copper into the ground already. I tore down a 1999 deck last summer and the bottom of the boards were almost gray while the top looked fine. The real issue is whether the remaining copper is enough to stop rot, not just rust on screws. I'd be curious to see if anyone has done a simple cut test on old boards to compare the visible treatment depth.

josepha3211d ago

That's a really good point about the leaching... I've seen the same thing with older decks where the bottom is just gray and crumbly. I actually did a simple test back in 2018 where I cut a few old boards from a 2002 deck and sprayed them with a copper test kit you can get online. The top half inch had some color change, but the middle and bottom were basically clean wood. So yeah, @kellyjones, I wouldn't count on 20 year old deck boards holding enough copper to stop rot in a shed floor. You'd be better off buying some fresh treated lumber for the floor and just using the old boards for something like a quick fence or a raised bed where rot doesn't matter as much. That cut test is dead simple and worth trying if you really want to reuse them, just cut a cross section and see how deep the green goes.

michael_coleman1010d ago

Yeah, cutting into one really does tell you everything...