Can pressure-treated deck wood rot?
In short, the answer is yes.
Given enough time pressure-treated wood, even that rated for ground contact, will deteriorate and rot.
The bases of every post of this deck had rotted.
My pen is sticking into this one, and I could have pushed it further.
How long does it take to rot?
That depends on the grade!
If an inferior grade is used on decks, particularly if the wood extends below the surface of the soil, it will rot in only a few years.
Grades start at .25, and the wood will be labeled with the grade. The best grade (marine) will have a .6 label.
While more expensive, the best grades will last for decades.
The subject house here is 29 years old.
How old is the deck?
Hard to know, but perhaps not that old as the guardrail stiles have a modern distance between - 4" or less - so that would date it later than 1998 in most jurisdictions around here.
Was an inferior grade of pressure-treated wood used for this deck?
Again, that is hard to know, but it's possible, if not probable.
My recommendation: it pays to look at the base of every deck post to see if it's stressed, or even rotting. Every single post on this deck showed rotting wood. It was affecting the deck above as there was a downward slant at a couple of corners. Sooner or later things will reach a critical point of damage and simply give away. Pay attention! You don't want that to happen when the family, or visitors, are all assembled on the deck for something fun!
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560