Install Trex over pressure treated 2x6's?

raylo32 · 04-02-2010, 12:21 PM

My 15 year old PT deck is structurally solid but the 2x6 PT deck boards (on 16" center joists) have a lot of weather and sun damage... splintering, cracking, etc. I could rip them up and replace them in kind with Trex 5/4x6 decking boards (Trex says 100pSF with 16" centers).

But I was thinking it would be easier and result in a stronger deck to simply place the Trex boards right on top of the existing PT boards and screw 'em down. They are the same width as the PT so the spaces would also match up. Also my threshold is sufficiently high that the new level would be 1/2 " below the threshold instead of the current 1 1/2". No problem there. Also, the additional load due to the weight of the boards really is insignificant. But I was wondering if there any downside to this, like the contact between the Trex and PT causing rotting or other issues? Anyone tried this? How did it turn out?

Scuba_Dave · 04-02-2010, 12:30 PM

Have you checked to see if that is an appoved method for installing Trex ?
If not warranty is void....and I'd say its not an appoved method or one I would do
Do a search on the site & read about others experiences with Trex

**kwikfishron** · 04-02-2010, 12:35 PM

I wouldn’t even think about it.

I’m sure our PT decking is a dipped and not pressure treated with little holes in it. If it’s dipped it’s rotting form the inside out. every ware its cracked is were water gets in and starts that process. You “will” have problems down the road and at the price of Trex you don’t need that.

raylo32 · 04-02-2010, 01:07 PM

Thanks for the quick response, guys. Whether it is an approved method is pretty much my question because I wonder if the prolonged contact, probably with trapped moisture, between the Trex and PT would cause early decomposition of the Trex. Maybe I'll call Trex and see what they say.

I built a Trex deck off my lower level back in 2006 and I love it. Just give it a quick pressure wash with my electric pressure washer every year or so and its good to go. I am currently staining my main level PT deck and *swear* this is the absolute last time I do this job... applying cleaner, pressure washing, allowing to dry, sweeping, then finally staining. What a way to ruin a couple of otherwise fine weekends. :-/

oberkc · 04-02-2010, 01:18 PM

Quote:

Thanks for the quick response, guys. Whether it is an approved method is pretty much my question because I wonder if the prolonged contact, probably with trapped moisture, between the Trex and PT would cause early decomposition of the Trex.

I don't know about decomposition about the Trex, but I can virtually guarantee that the underlying PT would decay due to trapped moisture. I would NOT do this, regardless of whether Trex approves it.

raylo32 · 04-02-2010, 01:23 PM

Well, I found an Install Guide at Trex.com and it allows install on a "solid surface" only by using a "sleeper system" that essentially raises the Trex off the surface to allow proper drainage and ventilation. My scenario is not exactly a solid surface but is pretty close, so I suppose it would not be a good idea. Oh, well, a little extra work to remove the old boards won't be that bad. I may even try the Trex grooved boards and use the hidden fasteners. But this will be a job for the future. I'm gonna finish my staining this weekend so the PT deck'll be good to go for another year or 3. Not perfect but it'll do for now.