"Anyway, I have heard it said that the tree is looking for moisture and nourishment and there is very little of either under the slab. Therefore the tree roots don't grow under the slab foundation and no damage results. I'm not an arborist, but it makes sense to me." Paul... About 12 or 13 years ago, I saw a heaved slab in a house with a slab-on-grade foundation. Since the house was 40 or so years old, I said, and wrote, something stupid like "the movement likely won't continue". Gosh I said some idiotic things when I first started. Anyway, I was greener than the large tree next to the house, not even realizing the tree's roots were the culprit of the heaval. Fast forward 10 years...my prior Client can't sell the house. Three home inspectors with three different buyer's all flagged the *abnormal and quite serious* structural movement. Naturally I got a call from my old Client. After meeting him at the house again, I realized what I missed the first time...roots from the large tree next to the house obviously had heaved the slab. And, thank goodness, my stupid ten-year-old statement had held; the movement did not continue. Thank goodness for mature trees. Anyway, I recommended a review by a structural engineer to add *meat* to the root assumtion. The engineer concurred, wrote a fancy report, the Client showed the report to the next buyer, and voila! May be rare, but perhaps there was a water source under the house. Goodness, that was the most sleep I ever lost over an inspection issue.