New Patio Area - Tie Into Raft

5 Nov 2008
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United Kingdom
I asked a similar question a few months back but now have some pics.

I have dug out the earth for my new patio - went down approx 10"
I plan to use a concrete mix as the base then i will be laying granite slabs on a screed bed, I want this patio to last for many years.

I will be slabbing over the raft foundation so that the slabs go right upto the house.

As the house will move over time slightly I don't want to have a lip on the patio where the house is moving slightly seperatly from the house.

Would it be worth drilling in 16mm steel ties resin fixed into the existing slab, I would drill in by 150mm and I can leave a good 600mm out in the patio base then pour in the sub base mix so effectively mating the 2 together.

I live in a soft ground area (what was pulled out was all soft clay) what concrete base mix would be best I was thinking C35 dry mix but this may be overkill?

Any thoughts chaps on both?

Thanks in advance.

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Something tells me not to rebar them together solid. The bar might help keep the two parts level but it won't stop the slab cracking. Personally I'd put a 10mm layer between the joint to induce a crack. You won't see it below the slabs and at least it will crack where you want it to. I'd also wrap the outer leg of the bar in a thin resilient material - maybe 5mm dense foam - to allow the bars to telescope. That will help restrain any vertical movement but allow a bit of lateral movement.
Thanks John

Anyone else with any options greatly welcomed

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