# Trex composite decking and waterproofing



## thompwa (Aug 26, 2019)

I'm rebuilding a second story deck approx 45'x8' in my back yard. The deck sits on top of a 45'x18' concrete patio. Couple of questions I have for anyone who has done this recently.

1.) Looking at using Trex composite. I realize it's bottom of the barrel as far as composites go, but I'm not looking to break the bank and it'll still be a heck of a lot better than what was there before. If you've installed it at your house, what has been your experience? Any feedback on simplifying install?

2.) since we entertain and spend a lot of time on the patio, I plan to water proof the framing (under the deck boards) to make it a place we can hang out even when it's wet. I realize Trex makes the rain escape system but I'm but not excited about the cost. I've found another DIY solution (link below) that seems to be a solid contender for about 1/4 the cost.

https://www.deckmagazine.com/design-construction/decking/installing-site-built-under-deck-drainage_o

Does anyone have any better recommendations for under deck drainage and waterproofing to create dry space under a deck?


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## daniel3507 (Jul 31, 2018)

My wife's uncle does landscaping for a living. Not the cut the grass and plant a bush landscaping but higher end backyard remodeling. He won't use any composite decking. He's had issues with with them warping over time, color fade, and it apparently gets pretty hot.


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## JP900++ (Aug 24, 2018)

Had first gen Trex at my last house. It does get extremely hot in the sun. We used the merlot color and it eventually faded to pinkish grey. That was 20 yrs ago so I'm sure they've improved. I would say go for the highest grade you feel "comfortable" with. I haven't looked into the under deck. Looks cool.


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## thompwa (Aug 26, 2019)

daniel3507 said:


> My wife's uncle does landscaping for a living. Not the cut the grass and plant a bush landscaping but higher end backyard remodeling. He won't use any composite decking. He's had issues with with them warping over time, color fade, and it apparently gets pretty hot.


Interesting. It's a tough argument. I can either 1.) use pressure treated boards and replace them every 7-10 years and clean/stain/seal them all the time for about $13/board 2.) go cheaper composite and pay $16/board and pressure wash it occasionally and get 15-25 yrs. or 3.) go with something like Azek and spend 3x that and it last for 30+ with almost zero maintenance.

Like many things, I guess it's just a matter of how long we plan on staying in the house lol


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## Gilley11 (Nov 3, 2019)

daniel3507 said:


> My wife's uncle does landscaping for a living. Not the cut the grass and plant a bush landscaping but higher end backyard remodeling. He won't use any composite decking. He's had issues with with them warping over time, color fade, and it apparently gets pretty hot.


My uncle had these issues as well. He spent around $15k on his deck. It was ridiculously hot to walk on, warped in many places and would constantly be covered in mold. It was TREX brand. He followed all of the manufactures suggestions on cleaning it, etc, but the mold kept coming back. After a VERY lengthy process, they eventually sent a crew out to replace it. Same thing, over and over again.

I used to always look at the demo decks outside of HD and unless they were new they would always be covered in mold as well. I never see them on display anymore.

Personally, I don't care of all of those issues hands been fixed, all of that is ingrained in my memory and I'll stick with PT lumber and stain as needed.


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## thompwa (Aug 26, 2019)

Gilley11 said:


> daniel3507 said:
> 
> 
> > My wife's uncle does landscaping for a living. Not the cut the grass and plant a bush landscaping but higher end backyard remodeling. He won't use any composite decking. He's had issues with with them warping over time, color fade, and it apparently gets pretty hot.
> ...


Well that sucks. I'm in North Alabama so it's going to get beat up in the heat. Had planned on framing it 16" OC to help with the warping. I know that's what Trex calls out in the install. I don't think mold will be an issue with mine, but definitely worry about warpage.


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## driver_7 (Jun 28, 2018)

A resort condo we visited many times over the years on the beach in FL had Trex decking on the walkway leading to and from the beach and beachside sundeck. It was blisteringly hot. They had mandatory shoes/sandal wearing signs after the first season. I would never use it on a deck that will receive direct sunlight after that experience.


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## FlowRider (Apr 7, 2019)

Trex decking will get so hot it will burn bare feet and dogs paws. Terrible.

I always use pressure treated pine and Thompson's Clear Wood Preservative in the five gallon cans. Spray it on with a dedicated hand pump sprayer, back brush it to ensure smooth finish.

Wood lasts much longer, protects against UV rays from sun, prevents wood checking, cracking or splitting, and keeps away mold and mildew.

Water beads right up. Last deck I used it on looked brand new after 19 years. Lets you see the wood grain too.

It would get hot in the sun too, but if you spritz it with water first, you can walk on it barefoot, and your dog(s) can too!

I believe Thompson's is mostly vegetable oil based - it penetrates and seals the wood beneath the surface, and sprays easily and fast.


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## Gilley11 (Nov 3, 2019)

Thompson's is parrafin based and needs to be applied yearly.


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## FlowRider (Apr 7, 2019)

Gilley11 said:


> Thompson's is parrafin based and needs to be applied yearly.


Thanks, Gilley11 - I never knew that. It really does have the consistency of vegetable oil.

I put it on a deck and screened in porch that was only in afternoon sun. The roof over the screened porch protected the wood from sun, so it really held up well. I usually sprayed the outside decking every two years, and the screened porch about every four. It all held up really well.

When I sold the house, it still had the original wood on the deck and porch, 19 years later.

I really liked that it would let the wood grain show through. It would bead water too. Looked great!!


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## 440mag (Jan 29, 2018)

thompwa said:


> I'm rebuilding a second story deck approx 45'x8' in my back yard. The deck sits on top of a 45'x18' concrete patio. Couple of questions I have for anyone who has done this recently.
> 
> 1.) Looking at using Trex composite. I realize it's bottom of the barrel as far as composites go, but I'm not looking to break the bank and it'll still be a heck of a lot better than what was there before. If you've installed it at your house, what has been your experience? Any feedback on simplifying install?
> 
> ...


I'm not sure if it is Trex or another brand but, I guess I can chalk this up to one of the few times I've been "lucky" based on others' experiences as, our composite decking is perfect after 10 years. We are very very fortunate it only gets summer sun from 9am to around 1, 1:30 pm and I would never say there hasn't been some minor fading on the top deck but, NO real "warping" so to speak (that'd OISS me off! :evil: )

As far as waterproofing the under framing, here is what I did BEFORE fastening the boards to the 16" on Center joists / framing I bought rolls of the 25' long 6" wide adhesive-rubber-like-backed foil fronted door and window insulation and cut each roll into four (4) 1-1/2" strips. I then liberally brushed the top of the framing / joist boards down with copious amounts and multiple coats of acetone (denatured alcohol would probably work just as well). THEN I applied the strips to the top of each joist before we fastened the composite boards.

DOING THAT HAS PAID DIVIDENDS FAR, FAR BEYOND MY WILDEST IMAGINATION!!!!! NO (zero, zilch, nada) water gets "trapped" between the bottom of the composite boards and top edges of the joists!

I now use this trick on ANY exterior construction project (most recently along the stringers of 2 arched foot bridges I constructed in the back.

IF ONLY I'd thought about it when (before)our dock was under construction!!!! :roll:


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