Yes, the only difference is that when you plant a new tree, you can begin to control the roots before they cause problems. When installing a root barrier for an existing tree, you need to clean up the stray roots so that they can now be contained by the barrier.
It is a simple process, which can be done quite easily. The only downfall is you may have already begun to see the issues in your hardscape or plumbing that result from not having a barrier to begin with. For this reason, it is best to install a root barrier BEFORE there are obvious issues and damages accrued.
As a rule of thumb; any trees or plants near a hardscape should have a root barrier installed as soon as possible before damages have occurred and unwarranted expenses are accumulated.
If you are already experiencing damages to your hardscape or plumbing, you may contact us for further advice on how to take care of such an issue properly.