What I'm Seeing Now


Can Composite Decking Rot?

Can composite decking rot?

If you go to the composite manufacturer websites will tell you their products do not rot.

If you search on line and find home repair websites, or forum websites, you will read that there are complaints all over the country.

Personally I had never seen composite decking rot in any way, until this inspection.  The listing information indicated that this was a Trex deck, but there are many imitators so we could not be certain.  Still, it was composite material.

Walking under the deck and looking up I found that every board had some form of rot or fungus growing on it.

One problem I noticed immediately was that there was little to no separation between the decking boards.

Again, if you go to any of the  websites, and to the installation guides, it says there must be space left between the boards so water can exit.

It also says that composite materials expand a lot with heat.  What I gather from that is that during the summer each board would squish against the one next to it.  Why wouldn't that crush the edges, and expose the insides to water intrusion?

The decking in the photo is a composite product - recycled plastic and various forms of cellulose.

It is said that the cellulose component approaches 50% of the composite material.

Cellulose has a high sugar content.

Fungus LOVES sugar!

There were many areas under this deck where a multiplicity of large, bulbous, fungal growths could be seen.

So the answer to the question in the title of this blog is YES.

The upper side of this deck had been recently painted.  Perhaps that was done to make it look nicer, or perhaps to cover up black stains which had migrated to the upper side.  There was visible damage up on that side as well.  And walking on the deck it bounced a lot between joist supports.

Until this inspection I had never seen composite decking painted before either!

The various websites say its decking can be painted IF it is cleaned properly first (not pressure washed), and then a primer/sealer layer is put on under the paint!

Was that done here?  I don't know.

My recommendation:  like everything, proper installation of any product is essential.  In this case it appeared that the installation at least had a role in the destruction of this material.  If water can't be eliminated from anything it will sit and find a way in.  When cellulose is included in any material - like composite decking or  fiber cement siding - it will absorb that water and the water will encourage the amplification of microbial growth.  Fungi is its own phylum!  Fungi exists for a reason.  Its purpose is to eat and destroy.  If not we would be surrounded by and under tons of old, old everything!  So don't let fungus eat your recycled deck!



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 • March 02 2017 10:23AM
Can Composite Decking Rot?
Can composite decking rot? If you go to the composite manufacturer websites will tell you their products do not rot. If you search on line and find home repair websites, or forum websites, you will read that there are complaints all over the country… more
"All Our Houses Are Built Strictly To Code… " Part 2
"All our houses are built strictly to code… " Part 2. That was the focus of the previous post which considered the idea that we have been conditioned to accept a minimum standard in so many things. And we have been conditioned to… more
"All Our Houses Are Built Strictly To Code… "
"All our houses are built strictly to code… " That's what the young supervisor said to me and my clients when he showed up at the end of our pre-drywall inspection. Me - "Are you sure you want to say that? " Supervisor, smiling… more
This Was A Highly-Touted, And New, Hardwood Floor
This was a highly-touted, and new, hardwood floor. And it looked great everywhere! It was a very professional job. Except in the powder room. The toilet wobbled. And there was a hefty and dark stain behind and beside the base of the toilet. Since… more
This Is A Beautiful Light Fixture! But Don't Forget The Insulation!
This is a beautiful light fixture! But don't forget the insulation! This is new construction. The entry way featured an open ceiling with a circular, wrapping staircase leading to an upper level hallway that serviced all the bedrooms. A very… more
This Is The Most Attractive Clean Out Port Cover I Have Ever Seen!
This is the most attractive clean out port cover I have ever seen! A local builder who designs and sells only a couple of houses a year hires me to do inspections when the houses near completion. He considers it to be another layer of protection… more
Clogged Peek-A-Boo Dryer Exhaust Vent Opening - And Dangerous!
This is the clogged peek-a-boo dryer exhaust vent opening - and dangerous! I had to search for it. Knowing it was behind the house it took a minute to locate it. But there it was, the clogged peek-a-boo dryer exhaust vent. The underside of the deck… more
"Insulation To Be Evaluated And Improved By A Licensed…
The addendum list of requested repairs said, "Insulation to be evaluated and improved by a licensed contractor. " In the previous years this homeowner had done many home improvements with less-than-stellar results. At the inspection I said… more
New Construction Inspection - Would You Like To Take A Bath Here?
New construction inspection - would you like to take a bath here? I do a lot of pre-drywall and then final inspections on new construction. And it is ABSOLUTELY NECESSARY. We never know what we will find. On every inspection I do a sweep with my… more
Do You Have Mice In The House?
Do you have mice in the house? These folks do. And they don't know why. It's a bit of an unusual request to get me to try to determine why there are mice in the house. Usually that would be left to some pest company, and responding to some ad… more