pressure treated wood and aluminum

[perchin]

'wood will rot from the inside out'....

Nope. If you seal plywood, it is dried to about 5% moisture content after pressing. That water is referred to as 'bound' water, meaning that it is within the cells of the wood. Even pine lumber, which is usually dried to 15% or 19% (the grade stamp will tell you...KD19 means 19%) is in the realm of bound water as well. When you get to 30% or more, then you get to 'free' water, or water that is loose in the staw-like fiber that makes up wood. That is what rots wood, it breeds fungus and allows the fungus and microbes to feed on the wood.

If you seal the wood and it never comes to 30% or so MC, no rot can occur. If you wet the wood and immediately dry it, no problem. If water sits on wood and cannot dry quickly (read: under carpet or vinyl, or under water) then rot begins.

If it never gets wet, then no rot will occur. There are 2000 year old wooden chairs found in the pyramids...

Agreed... Boat manufacturers encapsulate wood everyday. If it didn't work they wouldn't continue this method for the last 60 years.

On a side note, I don't start milling my rough sawn until its moisture content is reading 8%.

 

[Howard]

MSUMOOSE: This is great information and all makes sense to me. I have seen allot of wood rot very quickly simply do to poor protection. I have also seen wood last to the elements outside for my life time with proper protection. Is it true when trees are cut at a young age that the wood is more vulnerable for decay?

 

[msumoose]

'Does young wood rot easier than old wood?'

Well, yes and no...and it depends. LOL

Back in the day, all wood that was harvested was old growth (meaning non-plantation) and some say it had more rot resistance than a younger tree of the same species. Hard to prove since there is not much, if any being cut. Nowadays, virtually all pine lumber comes from plantations, and most doug fir, spruce, and larch too. Being in the South, I know most all pine is harvested at about 30 years old, with most earlier thinnings going to chips or pulp. It is hard to get anything other than 30 year old lumber.

So to answer your question...maybe, but all wood is succecptable, just at different rates.

 

[HOUSE]

man...this was a great thread to read, thanks guys.
I bought pressure treated plywood to make my flooring because it was going to sit on top of untreated 2x4 crossbeams sitting on my boat floor. Do you think I'll be safe if I just coat the non-pressure treated 2x4's with that Spar Urathane and then cover the floor with carpet? The PT floor shouldn't have any direct contact with the aluminum of my boat. Does the corrosive stuff leak out of the PT wood and still get onto the rest of my boat?

Thanks...