Perishing PT deck built in 2009

[sleepy hollow]

I built my deck in 2009.  I used PT lumber from my favorite family owned lumber yard.  The decking was select pine 2x6's with the scallop grooves on the underside.  Manufacturer is Madison.  Tags on boards indicate LIFETIME warranty.   I stained the deck about a year after install and have kept it up ever since started with Behr and then switched to Siikens.  Deck is southern exposure in VA near DC.  

About 2-3 years ago or so the decking showed signs of rotting.  Actually it must have started earlier than that.  Anyway I finally got around to talking to the yard about it.  They have been great and so far replaced every rotted board, well I replaced them, the yard provided the boards at no charge.  Up to about 40% of the decking at this point.  However, the serious part is that the joists are also rotting.

This photo shows what I am dealing with.  I am quite sure the manufacturer will replace these, but it sure is a head scratcher.  The lower beams seem perfect, but the joists and decking are perishing.  

What the heck is happening?  Thanks.  

[attachment=20888]

[Willyou]

I had a similar problem. Check this out. Following these recommendation resolved most of my issues.

[joe1086]

Over the past few weekends I've been taking down a deck I built 30 years ago. Back then I used cedar decking and PT for the posts, beams and joists. Some observations....

-The 6x6 posts were buried 18" and sitting on concrete footers. I pulled them out this weekend and they were in perfect condition (!). 
-The 2 x 10 deck joists that were protected from the weather were also perfect.
-Deck joists exposed to the weather showed fair amount of rot from the nail penetrations and they wouldn't be able to be reused.

We also had 6 x 6 PT used horizontally as landscape borders. They had been half lapped at the corners and they completely rotted everywhere there was a cut into the face of the post (but posts only cut to shorter lengths were fine).

Bottom line, moving forward....limit and seal the on punctures on horizontal surfaces. Going forward, we'll use joist sealing tape for the deck joists.

The PT material used 30 years ago was much better than what's currently available.

[CLETUS]

Wow... Those joists don't look like they were treated. They look much older than 10 years old.

I see what appears to be mold growing in the top of the picture... Is it alway wet under the deck?

[Robert Adams]

Since they took the A out of CCA treated lumber it's been garbage. There are other treating processes that are very good but they are only available in certian markets and only through commercial suppliers. 

         The tape on top of the joists is mandatory these days. Personally I wouldn't use treated lumber for deck framing anymore. Start looking into using steel C purlins. Typically used in metal buildings but is being used more in decks as it's a one time build. They are easy to work with for the most part. I cut them with a regular circular saw. I have even used a cordless circ saw on them as well. A plain carbide blade cuts very well but a real metal circ saw is a better choice.

[hbmcc]

I can't address your location specifically. I only know it was colder than ****, poured rain, and was a miserable experience after a cross-country flight several Decembers ago. The link Willyou provided fits my area perfectly. After rehabbing my deck this summer, I can expand upon the article.

I won't get into post-2000 chemicals vs. CCA (pre-2000) differences, but do know that some of the boards can slip through the process without chemical treatment. The brown stains applied here are not the preservative, which is a greenish-blue stain near the surface. Also, some companies provide a better treatment process than others. I would never want punctured wood, nor dipped, on my deck, but my neighbor has one that is beautiful, in all its punched glory. 

Some unscrupulous enterprises will sell "landscape timbers" that have the brown surface but no treatment, nor tag. Wet-wood termites love those timbers. Treated wood always has the tags.

In our area, Pac. N.W., different species are used which impacts the durability also. The punctured wood is Hemlock which has poor natural durability but absorbs treatment well. It is also mangled by the puncturing process, and tends to disintegrate quickly. Our older, above grade wood is much more durable. It is Douglas Fir, which is naturally durable--historically used in maritime shipping.

Two versions of pressure treated wood are generally available. The end tags will state the distinctions. One is punctured (riddled) having 6/10ths inch chemical penetration. The punctured wood is rated for ground contact.  Those joists in your image appear to be "above grade" treated, simply dipped, with penetration to .4 inches. Your decking is smooth and also appears to be above grade treated. All this should be fine. You should paint cut ends and notches with a copper based preservative. The preservative does wash out so a second means of protection is necessary.

If you have enclosed the deck where ventilation is difficult (through seams only) it becomes an environment not conducive to use of above grade wood. Perennially wet. All wood needs to remain as dry as possible, or dry out quickly. Also, every point of contact between boards will encourage faster decay, mostly due to the wet environment created by the close proximity.

[K. L. McReynolds]

The old PT was CCA(Copper/Chromium/Arsenic). Worked very well. The claim the arsenic 'leaked' and was a danger was never scientifically proven to be true except in a few cases.

The replacement was ACQ(Alkaline copper quaternary) with the quartenary being the bug damage preventer and extra copper being the rot resistance. Basically caused regular deck fasteners to corrode away in less than 2 years----decks were literally falling apart. Necessitated a complete change in deck fasteners.

The early ACQ treatments were junk. Three reasons. Newer fast growth wood has wider growth rings and is much less dense than the older woods. Water rots that type faster and the copper/alkaline cannot prevent it like the copper/chromium recipe did. Second, the treatment pressures were not sufficient nor long enough(due to having to replace the entire stock of the US in a very short time.). Cutting a board almost always revealed the core was unsaturated---and lumber rotted from the inside out.  Third, most of the lumber produced in that early period was shipped straight from the pressure treatment---and much of it was actually still dripping wet.

The time frame of your deck was in that time frame.

What has happened since the reduction in supply of CCA treated wood(not banned, just more difficult to get) is preservation of the building materials has become much more involved and expensive. It took time(10-20 years) for builders to get up to speed on what worked versus what did not work.

[sleepy hollow]

The old PT was CCA(Copper/Chromium/Arsenic). Worked very well. The claim the arsenic 'leaked' and was a danger was never scientifically proven to be true except in a few cases.

The replacement was ACQ(Alkaline copper quaternary) with the quartenary being the bug damage preventer and extra copper being the rot resistance. Basically caused regular deck fasteners to corrode away in less than 2 years----decks were literally falling apart. Necessitated a complete change in deck fasteners.

The early ACQ treatments were junk. Three reasons. Newer fast growth wood has wider growth rings and is much less dense than the older woods. Water rots that type faster and the copper/alkaline cannot prevent it like the copper/chromium recipe did. Second, the treatment pressures were not sufficient nor long enough(due to having to replace the entire stock of the US in a very short time.). Cutting a board almost always revealed the core was unsaturated---and lumber rotted from the inside out.  Third, most of the lumber produced in that early period was shipped straight from the pressure treatment---and much of it was actually still dripping wet.

The time frame of your deck was in that time frame.

What has happened since the reduction in supply of CCA treated wood(not banned, just more difficult to get) is preservation of the building materials has become much more involved and expensive. It took time(10-20 years) for builders to get up to speed on what worked versus what did not work.

[sleepy hollow]

Thank you for the replies, suggestion and information.  

I have suspected all along that this is related to the move form the older "green" wood treatment to the newer ones.  Funny how "science" seems these days only to prevent us from doing things rather than enabling us.  Then we have to recover and it costs enormous amounts of time and money.  Such waste.  We go from banning DDT which deloused the world to toxic mercury fluorescent lights to the "vaping crisis" that is likely more about using the devices to administer other dangerous toxins than about actual vaping of nicotine.  The nanny state just gets worse and costs us more time and money and momentum.  Hysteria is a very profitable business in a world where people are thoughtless and clueless about how things work.  Better to be a coffee expert than know how a wall is constructed.  Watch out the sky is falling because of too much CO2!  Oldest con game in the books.  I guess we know why now.  It works extremely well to enrich a lot of people.  

Enough of my soap box.  There I feel better now.  

Thank you all for the posts and suggestions.  

The deck boards are rated for ground contact believe it or not.  I have since been told about the tape, but I don't believe it would have made any difference based on what I am seeing, and considering McReynolds' post.  Maybe I am wrong, but that's my take.  You can see in the photo that both joists are equally decayed and only one took any screws.  

The deck gets a lot of rain and VA is perennially humid, so water is always present.  But that does not explain the advanced fungal decay on these boards.  I suspect a poor/flawed treatment process.  Again, McReynolds adds weight to this inference.

I actually flashed some of the joists just above where they sit on the main cross beam with 30# roofing felt thinking that could be an added protection (I had some leftover from another job).  I know felt lasts a few years but did not expect anything more than that.  This stuff appears to have begun rotting the first day it was installed.  Some of the boards decayed and some did not.  Actually most of the boards decayed, about a quarter to a third look good.  So, I think it is the process that failed.  Got a bad batch I suspect.  McReynolds again.  

BTW, the replacement boards seem to be much better, but way too soon to tell of course.  I need at least another 6 months to a year to see.  

I like the metal joists suggested by one of the posters.  But I expect Madison will replace the framing boards so I will have to decide what to do at some point.  Lot of had work ahead re-manufacturing my deck either way.  


I don't mind the rebuilding and reassembly.  That part is satisfying.  It's the disassembly that really irks me.  That's a lot of screws.

[Cub_Cadet_GT]

I don't mind the rebuilding and reassembly.  That part is satisfying.  It's the disassembly that really irks me.  That's a lot of screws.

Hey it could be worse 


This spring I had to demo about 600 sq feet of decking with rusted hot dipped galvanized nails. I would have killed for it to just be stainless screws.