Depends on which one, some are small, less than 10ft others are large trees.

generally think of the spread of the canopy when mature then treble that distance at least.

Hi, I agree with Sbg as regards the planting distance, but if you want to plant 1 away from the house, then as far away as you like, but if it's a Japanese maple, [the fancy Acers], just make sure it's in a fairly sheltered spot, out of any cold wind, Derek.