Trouble with cutting down trees is that it can cause as much subsidence as leaving them in place. As the roots of a removed tree rot away, the soil sinks into the spaces left behind. Also trees remove a tremendous amount of water from the soil. Once gone that water has to go somewhere else.
Personally I would leave it, at that distance any damage to the property should already be apparent. So if, no cracks etc. then the roots are not doing any harm.
If really worried then call out a Structural surveyor, expensive but ..........

I would have thought that it would be pretty safe at that distance. My contention would be that the main roots wouldn't be under the lawn as the grass would make the subsoil dry so the roots wouldn't find any moisture beneath. If you are still concerned then I would dig down in the bare ground which faces the house to sever any roots.

I would leave it unless you want it gone,ive learnt my lesson as owdboggy says where will the water go,everywhere in my case

Can't see any problem with leaving it where it is. Elders are only small trees even when mature. A spray of the flowers scalded with boiling water in a jug makes a lovely tea and the berries feed the birds if you don't want to use them in the kitchen. (And they do say that the witches are angry if you cut one down...

Don't they say that a trees roots spread as far out as the top growth? At that distance from the house I wouldn't worry and as Stera says they are a pretty tree, with flowers and berries and they don't mind how much you hack into them!