When laying on top of existing concrete the important thing is ensuring that your new slabs do not raise the patio level closer that 150mm to the damp proof course of the house. That was my problem as the existing patio level was at 150mm. I got around it by leaving a gap of 6 inches from the house wall before laying the first slab. I then used the 'five spots of mortar' per slab method of laying so the water could freely drain under the slabs. The gap between the first row of slabs and the house wall was filled with decorative stone chips. Furthermore I got some aluminium mesh (as used for car body repairs, which I purchased quite cheaply off eBay) which I cut into 3 inch strips then folded in half, so I made an 'L' shape to lay against the gap under the edge of the first row of slabs to prevent the stone chips from washing down under the slabs. I could have just as easily use large stones, but 'she who must be obeyed' didn't want the larger stones!
They've been down a while now and all is well
They've been down a while now and all is well
