Hoe do I stop /remove tree root spread

I don't know that you could stop regrowth if the plants are still present.

I think a raised bed would be quite a good idea there.

I guess Roundup could be the answer, especially if there is going to be a raised bed on top.

Is the raised bed for shrubs and plants? Perhaps a plastic liner under the new topsoil would assist also.

I've read that you can put a vertical barrier in the soil, I guess it would be metal or concrete slabs. All sounds a bit like heavy work. I've got an area at the bottom of the garden that is under trees. We made a raised area and filled it with soil, the tree roots won't grow upwards into it. It is held in by breeze blocks that are fronted by a brick wall with steps up to it. Make it deep and sturdy.

Can you be a bit more specific if you leave in stumps there may be sinking as they rot?

If you use roundup on the roots, you risk killing the shrubs the roots belong to - if that's what you want to achieve, you'd be better off removing the shrubs by digging them out.

I thought roundup only worked on the green parts of plants? That said as Bamboo says anything that kills the roots will kill the tree/shrub. Create a raised bed with a membrane - the black stuff you put down to suppress weeds will work. Then the roots will stay below the membrane and the plants can happily live on top.

There's a new version out that can also be used as a brushwood killer - that would kill root and branch (if it works, that is)

Must remember that if we have a really serious problem

A mechanical barrier, of corrugated plastic sheet was able to stop Bamboo from spreading, so should work on other less agressive tree roots. I sank it about 1ft. deep. but trees might need to go down a bit deeper.