The Brew Cabin

I am doing a new landscape for my garden. I am extending the patio and laying stonemarket flags . The old patio is laid in a 4 inches solid concrete about 30 years old , in good condition . I would like to know if i can lay the new flags in this old concrete subbase and laying a new one for the remaining part of the patio .

There's nowt to stop you laying the Stonemarket flags over the top of the existing concrete base, Marcio, but have you enough depth below your dpc? Remember: in an ideal world, the paving should be at least 150mm lower than the dpc. If your existing concrete patio is already 150mm below dpc, then laying a 40mm thick flags on a 40mm thick bedding layer will bring you dangerously close to the dpc, and that's just the sort of thing that Surveyors pick up on when/if you come to sell the property.

There's a couple of pages on the site that might be worth reading - the Laying over a Base page deals , primarily, with block paving, but the principles involved are the same. The DPC page outlines a few 'workarounds' that might be feasible in your situation.

Where you want to extend the patio, then laying a new concrete sub-base makes sense, and would be the best way to do it, assuming the dpc problem is resolved first.