Question
Recently my neighbor podocarpus trees roots have lifted the concrete of my swimming pool on my back yard.  When we informed him about this he cut down the trees that caused this problem.  We had several estimates and the lowest bid was $10,000 to have this fix.  We are working with their insurance co. to get this repair.  But that was not the end of the problem the podocarpus trees that he had planted on the side has also lifted one of our flagstones on the side.  We had a discussion about this.  He cut the surface roots and told us that would take care of the whole problem.  That was not the case when the landscaper remove the flagstone to see what was underneath, there were tree roots spread out everywhere.  There were several huge roots that have grown all the way towards our property. The pipes were completely filled with roots.  There were also small roots everywhere.  We told them this is becoming a major problem.  This problem has raised the soil level on the side of our property and needs to be level.  The roots that they cut needs to be removed otherwise it will rot and damage our flagstones.  This is going to be another major expense that we are getting estimate. The neighbor doesn't see it that way he had a tree person he consulted that told him the roots doesn't cause any of these problems and that cutting the surface roots will solve all problems.  What are your thoughts on this?

The following are also questions we have any help is appreciated:
1)What are the damages that the 13 podocarpus trees  each 25 feet high that they planted on the side will cause in the future?  These trees were planted about 5 inches from the fence.

2)If the tree roots that they cut, were not removed and it remains underground, when it rots doesn't that break the flagstones?  

3)Doesn't the roots underneath raise the soil level and changes the elevation?  Before flagstone can be laid down what is the process?

4) How far do these tree roots spread out to?  There were also small roots all over are these going to cause any damages?

5) What are the remedies to prevent these roots from growing over to our property?

Thanks

Answer
Sandy, unfortunately these are not the types of questions that one can answer in great detail without visiting the site and seeing the actual circumstances. My thoughts are you need to cut down the trees, build a root barrier or eliminate the hardscapes.
1. I have no idea what problems may be caused in the future as it depends on where the water is, and what open areas are available to the tree to get water and finally what physical barriers may be in the way of the roots that would exclude them. Roots tend to go where the water is.
2. Rotting roots will not typically break stones. But they may leave unfilled gaps and if they lifted up the hardscape slowly over time and then rot very quickly they may cause subsidence cracks.
3. Roots don't typically raise the soil level in mass. The roots themselves typically raise and break through the surface of the ground. You need to remove all the roots down about 6" minimum to level the pad for your concrete and flagstone.
4. Unfortunately I can't tell you how far the roots will go. It depends on water and physical barriers. Many trees species can spread 3 to 4 times their own height.
5. Build a root barrier to stop the roots. Most trees roots only live in the top 18" of soil. Unfortunately there are few if any resources on tree roots to tell us how deep a specific species grows. But typically if you can build a solid wall (poured concrete) or install a heavy duty plastic root barrier to a depth of three feet, it will then preclude the roots from entering your property. Google root barriers to learn more.

Good Luck