Answer: Holly trees can grow quite large over the years. Although the roots should not cause problems with the sidewalk, I would be concerned that eventually the branches will rub and scratch the walls of the new sunroom. Since the plant is still small and you have an opportunity to move it before constructing your new sunroom, I would move it to a better place in the landscape. One where it can grow to its full potential without being crowded - or crowding your building. There are other shrubs you can place in the spot that will remain small and not cause concern in the coming years.
Best wishes with your landscape!
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