How close may a tulip poplar be to a house and not pose the threat of root damage to the slab foundation?

Our 10-year-old, 30' tulip poplar tree was about 16 feet away until we added on to the back of our house. Now it's only about 6 feet away. It's beautiful and provides great shade where it is really needed. We don't want to cut it down if it poses no threat to our foundation.

How close may a tulip poplar be to a house and not pose the threat of root damage to the slab foundation?
"Liriodendron tulipifera - tulip poplar: Big with a capital B. Fast growing, attractive, native tree - but don't use it as a street tree or plant it 10 feet away from your house. Not particularly strong-wooded. Large, tulip-like flowers are among the prettiest of all tree flowers. Not tolerant of construction damage, and large beat-up tulip poplars left standing near a new home should be regarded as hazards, not assets."





I'd personnaly recommend more like 15-20' as the average root size for a tree covers its umbrella (size of upper foliage). If you don't have a depth foundation (ie. no basement) you should be alright, but I'd watch closely as you could have problems down the road.