The gravel will be your best bet. The deeper the gravel the better off you'll be from heaving and sinking effects. Compact the gravel as much as possible by doing it in 2-3 inch layers. Also does your existing patio have a drain? If it does than you might have a problem with the sand washing away over time. You can find edging where you buy you pavers, it is generally a poly material and is held in with 9-12 inch spikes. BTW you don't have to use a spike in every hole. After that is all done you'll have to raise the level of the lawn or beds to match the patio height. Or.....take out the patio and put down gravel and do everything the correct way from the beginning and have "piece of mind". Good luck

The contractor surely is suggesting to lay them in a mortar set over the existing concrete right? If so, it works but better be done properly or else one stone coming loose will be very difficult to repair. The surface joints too would need to be well mortared and sealed to prevent any moisture from entering, and don't forget expansion gaps. Laying a gravel base over concrete is an even worse idea IMO. Doesn't compact and creates an impermeable foundation beneath what little gravel base you may have. Furthermore it leaves your entire patio susceptible to any movement experienced by the concrete slab. Gravel bases are used in our climate in part due to their flexibility. In the end I wouldn't do it for a client and if I did I wouldn't warranty it. All that said though, you do have an opportunity to install what I consider to be one of the nicer and more underrated outdoor ground surfaces- reclaimed red brick turned on edge. One of my favorite designers James Van Sweden is big on this as it creates one of the warmest and most transitional (home to exterior) ground surfaces as well as being very amenable to patterned desings. Would need to work with your home and greater landscape though.

Sounds like it will be beautiful however spendy it may ultimatly be. How thick are the pavers? And you want to drive over this? We are also in Pa and I would be VERY leary about doing this. I know someone in eastern PA who did one inch thick slate pavers in concrete on their patio which was concrete. They are cracking- been in about five years. I have another friend who has a paver cobblestone driveway set in sand with a gravel base. This has been in about 15-18 years. Still looks good. If he's done this before and its held up - have him guarentee yours and go for it. Would be completely intallation technique sensitive.

No, in my opinion what you want to do is NOT feasible. According to The Tile Council of North America's, HandBook for Ceramic Tile Installation, that is not a recommended surface. They are the standards all tile manufacturers recommend and installation professionals adhere to. They are tried and true methods of successful tile isntallations. Installing over it, even with a cementious leveler "to fill in the gaps", would probably void the manufacturers warrenties and have a high risk of failure. Will it work ? who knows ... to do so would be rolling the dice in a gamble ... you might win and you might lose.