Concrete floor on a patio?

[concretedan]

Hi all,

I've just joined today and already this is my second request for some advice!!

I am planning to increase the size of an extension I have on the back of my house (1956 semi). It is currently 3 x 3 and I'm hoping to extend to 3 x 6. Where I plan to extend is currently a very solid patio. Can I knock out the patio for my footings and leave the reminder in place to lay a new floor over or do I need to get it all up and relay 150mm hardcore, binding, etc.? Any advice or guidance would be greatly appreciated.

Many Thanks,

Dan

 

[r896neo]

Whether it seems solid or not I think you would be crazy not to lift it. Even if you wanted to chance it, you are building a habitable extension and building control would not let you away with it. Not to mention the levels will probably be too high as you will obviously need insulation etc.

You would need to excavate in the region of 1 ft for 4 inches of hardcore 4 of insulation and 4 of concrete. Not to mention another few for screed if needed.

 

[RedHerring2]

It does depend on the height clearance that you have now.
I was in a similar situation, but I had about 600mm concrete patio below the proposed ffl. BCO asked me what I was going to do and I said I'd break it up but leave it in situ. He suggested no need, just go straight over the top of it.

So, if you have the clearance for new sub structure as r896neo explained, just go straight on top of it. But check with your BCO first.

 

[r896neo]

A solid slab of concrete is a different matter but any kind of flags, crazy paving or block paving would need to come up. Afterall it could well be layed on sand or who knows what.

 

[noseall]

As Red has stated, as long as it is deep enough not to hinder the floor laying process and there are no contaminants within then it will be no worse than having sub soil.

 

[concretedan]

Many thanks for the quick responses. I will be taking the patio up and digging down to allow for new hardcore, etc.

Thanks again,

Dan