Large oak tree 15' from house...

depends on your soil. A treein sandy soil will pose a threat of damage in high winds. Most oaks are pretty sturdy. Live and Swamp oak can lose big branches . is the oak hollow? any lightning damage? any bracket fungi growing fom the base?

most root damag e is near septic tanks and tile fields.
Id be most alert to damage from toppling or busted branches. we had a large ash tree that was close to the house, we had it taken down when we discovered that black snakes and squirrels were getting into the house by dropping fom branches onto the porch roof
also a high wind ripped a big branch about 24 inches in diameter and tossed it right next to the back stoop. We just had a new metal roof put on and the roof was missed by inches. So we had about 6 cords of firewood and our neighbors had all the firewood they could carry away.

Thanks farmer. That's what I thought. The foundation appears to be pretty damn thick and sturdy. It would take some some fairly strong roots to cause any substantial damage.

my comment about soil is serious. Weve had a lot of rain back home in Pa this year and , in certain areas where the soil has remained saturated or has low cohesion big trees have been blown down in thunderstorms. The tree acts like a big sail and it comes up , roots and all, sometimes causing considerable damage.

tree roots can get into old drain pipes, clogging them.

if the pipe is anywhere near the tree, it would be well worth the $ to get a plumber to snake a camera through it.

in march we had poor drainage. turns out our drain line was about 80% clogged with the roots of an azalia plant, which i subsequently replanted on the other side of the yard, away from the pipe.

good evening...I don't think the roots of the oaks will pose a problem to your house. Oaks grow deep; really deep. Watch out for maples (and I guess azaleas) which send out roots shallowly and can cause problems.
I've got two oaks (white oaks) 15' from the house and only 6' apart. Two people can stretch their arms around each tree and their fingers will not touch.
We've lived here for almost 30 years and I have spent, perhaps, $6000 on those trees. Things like farmerman mentioned: keeping them from getting top-heavy etc.
There is (or ought to be) an old Native American expression about oaks: 100 years to grow; 100 years to live and 100 years to die. If you buy this house, you assume responsibility for some few years of that cycle. realjohboy