What I'm Seeing Now


Can Pressure-Treated Deck Wood Rot?

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


Comment balloon 12 commentsJay Markanich • January 12 2017 11:01AM


Good morning, Jay Markanich you get what you pay for.... wouldn't that post have had a longer life had it been sitting on a metal cleat? 

Posted by Barbara Todaro, Marketing Agent for The Todaro Team (RE/MAX Executive Realty ) about 2 years ago

Arsenic not used now so what is injected to make it last longer like the little debbie's dozie oats that will still look good three decades from now Jay Markanich ? What do you power wash and apply yearly to best stretch the life of a lake wharf cedar decking?

Posted by Andrew Mooers | 207.532.6573, Northern Maine Real Estate-Aroostook County Broker (MOOERS REALTY) about 2 years ago

Those posts wouldn't make me feel safe at all!

Posted by Kat Palmiotti, The House Kat (Grand Lux Realty, Monroe NY, 914-419-0270, kat@thehousekat.com) about 2 years ago

Our deck was intially treated wood...but "graduated" to synthetic no maintenance material...very happily.

Posted by Sally K. & David L. Hanson, WI Realtors - Luxury - Divorce (EXP Realty 414-525-0563) about 2 years ago

Barbara - in your area it is deeper, but here they have to be buried 24", and then sit on a concrete footer and separated by a little metal foot that nails onto the post.  But the .6 grade wood will last a long time, even buried.  Some deck guys soak them in copper naphthenate first, to increase longevity.

Andrew - this post from years ago might answer your questions.


And the deck guys routinely hate that post.  It's a gotcha.

They aren't, Kat!  You should have seen some of the leaning of the deck!

I have never seen a synthetic post S&D.  But I'm sure they are out there.


Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 2 years ago

Thanks Jay.  I need to send this information to one of my customers as we had a disagreement about this very subject.

Posted by Gabe Sanders, Stuart Florida Real Estate (Real Estate of Florida specializing in Martin County Residential Homes, Condos and Land Sales) about 2 years ago

Good morning Jay. It pays to be educated about using the right materials the first time! Enjoy your day!

Posted by Wayne Martin, Real Estate Broker - Retired (Wayne M Martin) about 2 years ago

Good morning Jay. Another informative and scary post. My current contractor also pointed out that mold grows on these types of decks too.

Posted by Sheila Anderson, The Real Estate Whisperer Who Listens 732-715-1133 (Referral Group Incorporated) about 2 years ago

The support posts are buried in the dirt? SMH...

Posted by Fred Hernden, CMI, Albuquerque area Master Inspector (Superior Home Inspections - Greater Albuquerque Area) about 2 years ago

Gabe - I'm sure the information is out there for your client to look up.  My post is not new info, but the photos are!

Get the good stuff is what I always say, Wayne.  If it's available, anyway.

Of course it does, Sheila.  Mold will grow on anything organic if the conditions are right.  I've heard that sloths move so slowly mold can grow on them!

Fred - here yes, 24" minimum, and from there on top of a concrete footer with a metal plate under the post end.  That depth gets it below the frost-heave line.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 2 years ago

Now that's scary.  That could really ruin your family picnic.

Posted by Stephen Weakley (Nationwide Mortgage Services) about 2 years ago

Stephen - maybe a bit hard to see at this size, but that yellow arrow is to draw the eye, pointing out how much the deck has sagged from the far guardrail to the exterior rail.

The downward movement has been about 4" from one point to the other.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) about 2 years ago

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