Question
I am in the process of putting in a egress window which requires that I dig down about 5 feet along my one side of my house. After digging down about 2 to 3 feet I started hitting some roots that I expect are from a large oak tree nearby.

The tree is about 30 feet high and it is located about 7 feet from the area that I am digging. I am worried that if I damage any of the roots that it could hurt the tree. The roots are fairly small, about 1 inch in diameter.
Thanks for any advice you could provide.

Answer
The majority of the roots are in the first 18-24 inches of soil. If you damage more than 20-30% of the root system you can expect some branch and foliage dieback on the side toward the digging. If you can imagine the shadow of the width of the limbs being a pie shape and you cut an amount off this shape if this is less than 30% of the total you should be ok as far as the tree recovering. It more than likely will have some dieback but will not kill the tree.