I am known for my contrary opinions here, so here goes again. I think you can cut these roots (you may want to treat the cut ends with liquid copper fungicide (search that and you will find my earlier postings). Why do I think it would be OK. You do have 17 feet--that's not bad. Plus, it is a corner, so you are not cutting off a swath all along one side of the tree. Finally, you will be reducing the roots of the tree by, I would guess, less than 10 percent. Earlier in this forum, under a topic I forgot the name of, I described what was done at Penn Alps in MD to a couple of Norway spruce trees--they were within 5 feet of the foundation of a new house that was built and most of the roots on one side of these trees were cut. This house is down wind in a very, very windy location and those trees as of now, about 5 years later, are still firm and have had no top deterioration.

Now I don't know anything specific about how redwoods would react to such disturbance, but I would guess that it will be at least as well. Roads have been built all through the CA redwood state parks very, very close to large redwood trees, certainly resulting in the destruction of the roots on those sides of the trees right next to the roads, and I don't see any of these trees dying, being uprooted, or losing their tops. The road through Humbolt Sedwood State Park and Prairie Creek Redwood state park was for many, many years a main US highway, so its base was very deep. I know these redwoods are very deep rooted in the alluvial soil there, but those roots must have been destroyed.

So, I would cut the roots, treat the ends with the 1/3 liquid copper fungicide 3/4ths water mixture I recommend (just to be on the safe side) and enjoy having your house built. But, But, But, be very careful not to disturb the other rooting area of this tree during construction--have it roped off, covered with heavy plywood boards, really, really thick heavy mulch or whatever for ONLY the period needed for construction. Don't have any extra soil put over the roots.

I think you are golden!

--Spruce