Patio Topping

We currently have a concrete patio that is 32'x11'.We want to expand the patio to 32'x16'.The old section is cracked in 3 or 4 places and is slightly uneven as the result of settling over the years.  I want to add new concrete on top of the old when we expand the patio. I've asked 5 different contractors about this and have gotten 5 different opinions on the proper way to do it. What methods would you use to best insure a good bond and less cracking of the new surface? It is under roof and the new section will be also.  Also what depth of concrete can I get by with?  I would like to go with 3 or 4 inches...is this okay?

GW/KR.....thanks!
Adding concrete topping to old concrete is tricky.

The safest way would be to assume that the old concrete is like soil - and add a minimum of 4 inches on top. Under these conditions it does not matter that they do not bond (a bond breaker will be best) or if the bottom slab is cracked. But this is more expensive and will change the elevation of the patio by much.

If the bottom is cracked, it may not be a good idea to bond them together.  The best way will be to place a uniform (4") slab as replacement. An alternative will be to leave the old slab alone and just add a new one next to it. They will never look the same, but you may add some architectural treatment that will make that acceptable.

Adding a topping that is bonded to the old slab is asking for trouble since the new material will shrink relative to the old, and result in new cracks. Even joints (which are a must in any slab - at 6-8 feet spacing) will not prevent cracks in bonded topping.

Hope that helped.