My concrete patio has a crack running across the width. I have just bought the house and am totally new to this home ownership. The crack is getting worse. The patio is surrounded by old, half-dead trees. How can I find which tree's roots are causing the problem? What can I do to stop the root growth? And after solving the two previous problems can I just repair the crack with some type of concrete repair compound? Many thanks for any help you can give me.