I have a concrete patio in the backyard, and when it rains water runs across this patio, the past the back door and toward the driveway. If I replace this patio with a pavers, will I be creating drainage issues at the point where it becomes concrete again "downstream"? Drainage is already an issue in the back door area - which is why I'm considering a re-do in the first place. I need to address an improper slope in the concrete by the back door and therefore need to rip part of the concrete up... so I'm trying to figure out whether to just re-do just that one area in concrete or if some other material throughout for a bigger overhaul would be best. Please note we have a concrete slab foundation.

I have a corner house with 2 big oak trees in front, and two on the side. All four are on the skirt of the concrete sidewalk. Three of the trees have uprooted the sidewalk to the point it needs repair. From each tree, there are 4 flags (4' x 4' x 4") that have moved, and the outer two on each cause a pretty big lip which is why the repair is needed. However, only one flag of the 12 has cracked, the others have simply lifted because of the roots. Near me, a flag costs $150. That means $1800 to remove and replace them all. Yet, all but one flag is in perfect condition. It seems it would make sense to lift each flag, chop away the roots, then put it back in place. And then just pour new concrete for the one cracked one. Easy enough--except for the 750 lbs they weigh. Actually, many are still connected as the flags are not installed separately, but have a line separating them. But I am guessing that a chisel and some movement will cause them to break apart at the line. Maybe that is what the line is for, for all I know. I have looked for ways to lift them but every source I find explains how to lift sunken slabs just enough to shovel some sand of gravel underneath. I would need to lift each slab on its side, then lower it back into place after chopping the roots. How would you guys handle this situation? Has anyone ever done this? Is it reasonable to consider?