# Concrete Decks



## Cache (Sep 18, 2007)

Usually use PT lumber and IPE for exterior decking. Been seeing a lot of decks with what appears to be a sanded and stained concrete surface lately. That is what this HO is looking for. For some reason I can't figure out what product they are using. Can't just be a standard grout mix concrete, or I think it would be cracking all over when applied over exterior plywood decking.

Any ideas as to what it might be?


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## Five Arrows (Jan 30, 2010)

*go up to the door*

Go to the door and ask the owner. When you find out post it. sounds interesting to me. Never seen it before.


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## dprimc (Mar 13, 2009)

There are many concrete polymer overlay products. (Google) I've used Concrete Solutions. Their product uses an elastomeric base coat, metal lath, a scratch coat with the polymer and then a top coat that can be finished any number of ways...stamped, stained, dyed, etc.


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## genecarp (Mar 16, 2008)

There are many synthetic concrete type materials out there today, overlays, etc....In general covering any type of a wood deck in any type of concrete synthetic or otherwise is a bad idea. If a customer wants a concrete patio, rip out the deck and do it right, GMOD...


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## Cache (Sep 18, 2007)

genecarp said:


> There are many synthetic concrete type materials out there today, overlays, etc....In general covering any type of a wood deck in any type of concrete synthetic or otherwise is a bad idea. If a customer wants a concrete patio, rip out the deck and do it right, GMOD...


I'm talking about a second floor deck. I really hate trying to build it in steel and concrete.


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## genecarp (Mar 16, 2008)

Cache said:


> I'm talking about a second floor deck. I really hate trying to build it in steel and concrete.




IMO, it's just not a good idea, you have a wood second floor deck, now you want to put something on top, lock in moisture, no breathability, when wood begins to rot, how do you make repairs? There may be some product out there that claims to be able to accomplish your goal, minimally it will be unproven in it's ability to stand the test of time, GMOD.


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## Cache (Sep 18, 2007)

genecarp said:


> IMO, it's just not a good idea, you have a wood second floor deck, now you want to put something on top, lock in moisture, no breathability, when wood begins to rot, how do you make repairs? There may be some product out there that claims to be able to accomplish your goal, minimally it will be unproven in it's ability to stand the test of time, GMOD.


No, it is a new build. I can build it however I want. Just don't want to build it in steel if I don't have to.


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## genecarp (Mar 16, 2008)

Cache said:


> No, it is a new build. I can build it however I want. Just don't want to build it in steel if I don't have to.[/QUOTE
> 
> 
> 
> That's a little different, let me think, G


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## RobertCDF (Aug 18, 2005)

Happens a lot around here. (ENGINEERING REQUIRED) frame it to the specs from the engineer with a 1/4" slope. Sheet with PT ply AND WATERPROOF!!!!<--- CRITICAL!!!! and then have your flatworker build forms around the outside and pour as normal and finish however they desire. 

I have also seen some fail when they did not waterproof properly. The slab cracked and water ran BEHIND the stucco paper and rotted the beam holding it all up...Pay close attention to all flashing details because people are going to think it will last forever and therefore they wont be on the look out for signs of failure. Imagine being under a 12x20 deck with 4" of concrete when it fails...


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## dprimc (Mar 13, 2009)

Not at all saying this is a good idea!!!

But if this is really the route they want to go, there are all kinds of proven elastomeric coatings that work with polymer concrete. Seal your plywood with one of these to start.

Then apply ice/watershield, and metal lath for polymer scratch coat.

Then concrete polymer (also proven) and guaranteed to hold up better than reg. 4" concrete over time in an environment with movement ie. 2nd floor deck.

May not be a good idea, but a sealed polymer will last way longer than standard 4" slab. Cracks will occur in both, but the cracks in the polymer should be smaller and the ice watershield and elastomeric should keep it from damaging the wood for a time.

Make sure you overbuild (go up a joist size, shortent the joist span, etc.) to help prevent movement.

Untimately it is designed to fail at some point. The polymer should privide a longer life, and also be cheaper to replace when it does fail. Make sure you have good ventilation underneath if they want to enclose the joist bays!!!!


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## griz (Nov 26, 2009)

Cache said:


> No, it is a new build. I can build it however I want. Just don't want to build it in steel if I don't have to.


What's wrong with steel?


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## cexcavation (Apr 17, 2008)

Build it in steel and sleep better at night. Seems like a waste of concrete, and a bit dangerous to build using something that inevitably rots. Just my opinion.........then again I am a metal fabricator and not so much of a wood guy!!!!:laughing:


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## genecarp (Mar 16, 2008)

I think basically what he is trying to do is build a second floor wood constructed deck with a synthetic concrete type coating that will mimic a real concrete patio. I would never consider putting 4" of concrete overhead on a wood framed deck. I beams and corrugated would be my first choice, GMOD


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## jimAKAblue (Aug 15, 2010)

Cache said:


> Usually use PT lumber and IPE for exterior decking. Been seeing a lot of decks with what appears to be a sanded and stained concrete surface lately. That is what this HO is looking for. For some reason I can't figure out what product they are using. Can't just be a standard grout mix concrete, or I think it would be cracking all over when applied over exterior plywood decking.
> 
> Any ideas as to what it might be?


Look into Miracote products. I haven't done any but I remember a nice thread from a guy that explained it over at BT when it was a decent forum. 

The devil is in the details but it will easily go over a deck and I don't think you need to pour 4". I think you only need about 1/4" of the stuff over a solid wood substrate.


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## MikeGC (Dec 6, 2008)

Deck builder magazine ads for concrete deck tiles 

www.dekstone.com 
www.silcasystem.com


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## Cache (Sep 18, 2007)

Thanks for the info guys.

Just to put some concerns to rest, there is no way I would ever consider a 4" concrete pour over a wood deck. The most I would consider is a 1.5" coating but even that adds about 10lbs/sf. Certainly I've been looking into products like Miracoat that would reduce that to less than 1". The concern is not the engineering as that is my background. The concern is the cracking. I know it will crack, I just need it to be somewhat controlled and not a spiderweb.


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## Cache (Sep 18, 2007)

Well, a thin (1/2" or less) polymer concrete is out. Visited three different installs that used that method in the neighborhood and all three had to tear out after one year at an average cost of $13,000. All three chose to go with Ditra, porcelain tile, and epoxy grout instead. It is performing wonderfully. 

I caught one of the homes right in the middle of demo on the old deck. The installer shouldn't have a license. Most of the problem was caused by improper install IMO. 

3/4" T&G OSB
Stapled down fiberglass mat
Poured a thin concrete product straight to that
Stamped, stained, and sealed

Someone forgot to tell him that concrete isn't waterproof. I've never seen deck joists rot out so fast in such a dry climate. If he had simply put down a coat of Redgard the deck probably would've still cracked, but at least the structure would've remained sound.

What if the HO had a bunch of grand-kids over who decided to go out and play on the deck loaded with 3 feet of heavy snow? Those rotten joists could barely hold me and the one guy doing demo.:furious:


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