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Decks/Pressure-Treated Wood


I'm currently doing a science experiment on different types of wood and their ability to absorb water (pine, cedar, oak, and pressure-treated pine).

What I'm doing is weighing .75"x1.5"x1" cubes of each type of wood, submerging them in water for 1 hour, then weighing them again- then finding the difference in weight.

I've always read that pressure-treated wood resists rotting, so I naturally thought that it would resist water the most. However, pressure-treated wood's difference in weight has been the greatest of all woods so far (I'm doing numerous trials). So it has appeared to absorb more water than all the other types of wood!

Do you know if there's a reason behind this? Does pressure-treated wood absorb water just as much (if not more in my case) than other woods, but it just resists rotting or something as I read? Is the size of the wood, or the time I'm submerging the wood a factor? This has been confusing me quite a bit.

Any answers would be helpful! Thank you!

Hello have you tested it against regular pine? both are porous also I would have thought cedar would increase the most weight wise, it is really porous. Also are you testing new PT or old already dried PT. It's my experience that new PT is really wet from the manufacturer and over time it dries out and becomes very hard ( it won't nail very well without splitting when it is dry) Try testing old pt verses new. That should give you alot different results hope this helped.  


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Eugene Clayton


I would be happy to answer any question reguarding the construction of decks, composites verses natural materials, structure support systems,railing applications,stair design, how to figure stairs etc.. Pretty much anything that has to do with decks and or porches.


I have been in the construction industry for over 27 years including new home construction, custom deck and screen porches. Most of my expertise is from framing custom homes for over 20 years. I now own and opperate a very successful custom deck and screen porch company in Atlanta Ga.

High school graduate

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