# Forum Home Renovation Demolition  Cost to remove concrete slab, and is it the best idea?

## Jon

We are planning to replace our existing steel patio with a bigger one, and the existing slab possibly needs to go.  Part of the new patio will be fully enclosed to make a games room (non habitable) to give our noisy teenagers a bit more room when they have friends over.   
The existing slab is around 18 years old and has sunk and pulled away from the house as shown in this picture.  This is probably because the fill it is on has sunk. I am not aware of it moving much in the 7 years we have owned the house. You can also see the height of the termite barrier and weep holes in this pic.  
The snapshot from SketchUp shows the floor area we would like to end up with with the square area in the bottom right area going to be the 5m by 5m outdoor room with the rest being normal patio with a steel roof.  The existing slab is shown in red.  
I understand how to extend a slab by using starter bars drilled into the edge of the existing slab to key the two together but is the existing slab too compromised for this with the movement? 
This is a rough drawing of what we would like to end up with.  The material for the floor is still up for debate and also depends on whether or not the existing slab goes or stays.  Tiles in the room area and wooden decking under the patio would look nice but it would be a zero height deck, especially if the concrete stays.  I would be happy with tiles in the room area with 300mm by 600mm pavers in the patio area.  
Is the existing slab worth keeping and adding to or should be we remove it and start afresh?  Access is pretty good as the garden that currently blocks access will be going. 
Jon

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## SilentButDeadly

I'd be doing everything I could to keep that. Cost to remove is basically labour plus gear plus cartage plus tip fees. Google tip fees for concrete per cubic metre    and use your imagination after that...

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## Jon

Yes, i would prefer to keep the existing slab but the movement it has had has me a bit concerned. 
TR

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## Bros

Not unusual for slabs to come away from existing structure due as you rightly assume different foundations. As for keying another slab in I would have reservation as it will be subject to its own movement and steel relies on a covering of concrete to stop it exploding the concrete and you would never get the new concrete to adhere to the old.
What you will also come up against is the tiles will never be a match to the new ones.
The best job would be a complete new slab but as has been said this is not a cheap exercise.

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## Jon

Thanks Bros  

> What you will also come up against is the tiles will never be a match to the new ones.

  The existing tiles will go  
Would laying a sheet product like Scyon over the old and new slabs in the room area and then tiling over it allow for movement between the old and new slabs? (if we end up keeping the old slab).  The other solution would be to bolt a ledger to the edge of the slab and build it like a deck with piers, bearers and joists and then use scyon sheeting. 
If we used pavers on the other end they would not have an issue with slight movement between the slabs.

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## Bros

Sorry I cant answer your questions as I was just pointing out the problems you will have if you try to attach a new slab to the old I have seen it done horizontally but in the end who knows if it was successful.  
One way out with the joining and I never knew it existed is to use 316 SS deformed bar, it won't be cheap but would solve the keying into the old slab problem but you will still have two slabs on different foundations with the new one on different soil so you could expect some movement until the soil moisture content stabilize.

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