How implicit can a building be to an oak tree?
You need to consult your structural fix on this. There is not a single hard and quick answer since consideration needs to be given to the type of soil ...Is it low, prevailing conditions or high shrinkability soil ? This will depend on your geographical location. Foundations can be designed to accommodate trees within some situations.
For example, an English Oak whose mature largeness will be 20 to 25 metres in big shrinkabilty clay soil at 6 metres horizontally from a building . Minimum foundation depth will be 3 Metres. Further foundation precautions will be needed such as heave precautions, slip membranes and compression panel.
I grew up on a 5 acre property on which nearby were 16 oaks of four different variety.
Since oaks are known for shedding branches, getting crown rot, and exploding from rot inside the trunk (methane buidup from internal rot next to no escape hole), I would site the house away from the widest spread of the branches estimated for a mature tree.
We lost section of our barn when one of our oaks dropped a 7" diameter branch one night. Another 4' diameter tree exploded 17 foot from the ground and the upper branches barely missed the house, which be 50' from the tree's trunk. Another 5' diameter oak fell over from crown rot, but it fell away from the house onto the front lawn. Needless to say-so, we had several years' worth of firewood from these disasters.
It's best not to reshape within 10 foot of an oak's trunk to prevent crown rot.
Answers: The best rule of thumb is that the roots extend as far underground as the branches do on the tree.
If the oaks are mature,growth will be a few mm respectively year.Saplings grow quite like greased lightning,so the answer really depends on the age of the tree.
With any new building within reach trees,it's important to consider the roots may eventually invade drains,or affect foundations.
Consider also the shade type by the tree and the possibility of storm damage cause branches to fall.