# Forum Home Renovation Decking  Decking over concrete outdoors?

## Shari

Can decking be put over concrete in an outdoor entertaining area? I suppose it can, but I was wondering what happens to dirt, leaves, rain etc over time? Does it just build up under it? Or can you lay outdoor decking with no gaps like an indoor floor??

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## UteMad

Laying decking without gaps is asking for trouble as it leaves no room for boards to expand and contract.. the gaps are 3mm or 1/8 inch approx so only things that small can get through.. Your best to batten your concrete with treated battens then fix decking as per normal.. If you screw the boards a board can always be removed to hose underneath if your that way inclined      
cheers utemad

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## Shari

Thanks for that, and great pics. Much appreciated.

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## Bloss

UteMad is on the money, not a problem to do, but care needs to be taken to allow water to go where it wants to go (to the lowest point) - it will flow under the decking and needs to be able to escape easily and without ponding. That means the positioning of the sub-floor (bearers & joists) and any sloping of the deck as a whole (can be level, but best with at least a little slope - the right way!). Just a matter of a little forethought and design, but I have had to do some heroic fixes to decks when it hasn't been thought about until the first big downpour!

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## UteMad

Best way to go is to pack the highest part of the concrete up 10mm even if it means taking a shave off the batten to reduce the packing on the lowest part.. this and trying to leave a few places to hose underneath all help with water running under the deck.. Trouble is most guys just lay the battens straight on the concrete unpacked that way they save on all the dyna bolts and packers and to a lot of customers cheaper is better til bitten.. I also like a glob of liquid nails landscape or eurethene between the packer and the concretre .. even though its dyna bolted it saves the packer slipping out and letting the dyna bolt go loose.. Looked at a commercial deck a while ago that they expanda foamed the battens to save on packers and fixings .. boy what guys will do to cheat on a job. 
good luck with it .. and yes we have batten some bad concrete with up to 300mm level differences and concrete stairs which are also great fun   
cheers utemad

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## Shari

Great, thanks for the tips!

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## BrissyBrew

> Best way to go is to pack the highest part of the concrete up 10mm even if it means taking a shave off the batten to reduce the packing on the lowest part.. this and trying to leave a few places to hose underneath all help with water running under the deck.. Trouble is most guys just lay the battens straight on the concrete unpacked that way they save on all the dyna bolts and packers and to a lot of customers cheaper is better til bitten.. I also like a glob of liquid nails landscape or eurethene between the packer and the concretre .. even though its dyna bolted it saves the packer slipping out and letting the dyna bolt go loose.. Looked at a commercial deck a while ago that they expanda foamed the battens to save on packers and fixings .. boy what guys will do to cheat on a job. 
> good luck with it .. and yes we have batten some bad concrete with up to 300mm level differences and concrete stairs which are also great fun   
> cheers utemad

  I have similar project to do at some stage but I dont have much of a drop between the concrete slab and the house.  
How thin could you go on the battens, for instance if you are screwing 50mm screws, 19mm decking I assume you need at least 35mm TPine for the batterns. I dont know if I have sufficient space as I would still prefer the deck to drop down slightly from the house level, just want to know how far I could push the envelope.

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## UteMad

Mate gone thinner than 35mm..  Not something i like to discuss to much PM if you want to know how to do it properly with thinner battens  
cheers utemad

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## NoClue

UteMad, 
I'm considering doing something very similar to your pictures. 
We'll get the slab installed so we can have heights more or less as required. What would be your suggestions? We'd want the finished height of the deck to be equal (or slightly below) that of the house floor. 
How much slope away from the house do you recommend for the slab? 
How high can you got with the hpackers for getting the level right on a sloping slab? 
Cheers, 
NoClue 
PS. I'm a long time lurker. Great forum.  :2thumbsup:

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## Bloss

If you are going to build a deck why slab too?  :Confused:

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## NoClue

I'm concerned about the amount of water that currently flows through the area. I think it'll be difficult to prevent water from standing under the deck. As it's near to the ground, I think it'll prove difficult to fix if the water become an issue.

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## R3N0-S

Hi  
You won't need a slab if you put down some sand and crushed rocks as it will help reduce and stop the water from ponding up underneath too much.

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## Bloss

> I'm concerned about the amount of water that currently flows through the area. I think it'll be difficult to prevent water from standing under the deck. As it's near to the ground, I think it'll prove difficult to fix if the water become an issue.

  That's simply about doing the correct drainage and a slab is not the way to achieve that. Putting a slab in the way will simply send the water somewhere else - you need to design so you control where that is. Since it seems accessible now, then now is when you need to get the drainage done and correct - then just build a deck.  :2thumbsup:

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