Answer: You didn't mention how much you need to raise the grade or what kind of trees you have. Some trees such as green ash and birch can tolerate a little more soil added to their roots, but oaks and some maples will not tolerate much at all. You will damage most trees if you add more than three or four inches of soil over their roots. The only way to raise the grade around them is to build wells to keep the soil off the feeder roots. The wells need to be as wide as possible, the diameter of the crown if possible. You could perhaps consider terracing your yard to raise the grade toward the house gradually.
I suggest you contact your county extension office for more information on the construction of wells, and perhaps a landscape contracting firm about the possibilities of terracing.
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