not a tree of heaven or a walnut.....tree of heaven have a single notch in the leaf toards the stem and walnuts do not have serrated leaves. Sumac in a possibility but not sure about the species. A big hint will be the fact that the tree has compound leaves.

How about a young pecan (Carya illinoenses)? Regardless, I believe that I would remove it from the side of the house while it is still considered small.

Thanks for the thoughts you guys. Yes, Tree_Man I think you are right. I had been afraid to cut it down if it was tree of heaven for fear they would pop up everywhere. At least now it's not so difficult to remove. Too bad it's so close to the house....

also - this shows the black walnut as having slightly toothed leaves - english walnut is smooth....

Here is a link that might be useful: black walnut vs. english walnut

First thought was walnut, though not sure they grow in Cali.

if you use stump killer ... properly applied to the cambian layer immediately after cutting flush to the ground ....things will not pop up everywhere ..

and you would avoid having to dig this out ...

and this would be a good place to do such.. as nothing should be planted that close to the house ... no matter the plant ... and you would avoid utilities.. if any ... dig safe

ken