, everything is treated. If it's not, takes about 10 years before the termites and rot
have done enough damage for it need to be replaced. They used to use a pressure treatment chemical that was arsenic and copper salts in a water
based mixture that left the wood green. It was primarily a surface treatment. The stuff intended for below ground use had a much heavier incrustation of the green chemical and the wood was deistressed to let the stuff penetrate deeper. Very effective but costly and probably now banned by the EPA. Dug up some of the above ground treated stuff that had been buried for ten years and it was still good wood. The untreated stuff buried with it was pretty much goo. Didn't seem to hurt people as Hawaii
has about the longest lived populations in the US. They are now using a pale colored treatment that is supposed to work as well and certainly isn't as yucky to work with. Doesn't seem to be as wet as the old style pressure treated wood was. Of course, the fairly dense Douglas Fir we used to get is history
. The new stuff is Hemlock and much softer and less dense. Curiously, the softer wood absorbs the treartment way better so is supposedly much longer lasting. It's still crappy lumber
compared to the old stuff.
I really don't understand why boat builders haven't used treated lumber
. It's light years more rot
resistant than untreated lumber, except for teak
. Especially since most wood boat building is cold molded or strip plank which don't need the quality of wood as carvel planked boats.