Safe deck surround distance for tree
The tree will generally grow larger in diameter centered around the existing trunk....at least for the foreseeable future. Larger / older trees may at times grow out more to one side versus another but the factors that cause them to do that are probably complex and may have more to do with how the canopy of the tree develops or how the tree gets damaged or stressed through the years. My experience is that most trees will attempt to grow around an obstruction as opposed to moving over if it gets a little crowded on one side.